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#1
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RC plane motor questions
I've been interested in small brushless motors for some time and it
seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. But what kind of signal does the ESC need? The same type of signal that RC servos use? Do I need to get a programming card for the ESC? And how is the rpm/volt detrermined? I'm thinking that I should get a kit motor to learn about them but I also want to get some regular motors to compare. It looks like Hobby King might be the best place to buy the motors from but I don't know. Any help would be greatly appreciated. Thanks, Eric |
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#2
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RC plane motor questions
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#4
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RC plane motor questions
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#5
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RC plane motor questions
On 06/23/2011 12:48 PM, Cydrome Leader wrote:
wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. I'm not sure what you're making, but the power to weight of those brushless motors is quite impressive. There's a catch though, if you're not using them to just run a fan, which is all they're good for. they lack position sensors, so you can't just spin them back and forth like a regular motor unless you have some sort of really awesome motor controller. They seem to now have brushless RC car motors and controllers. I'm not sure how those work though. I believe the brushless car motors have hall sensors for commutation, the same as an industrial servo brushless would. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html |
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#6
Posted to rec.crafts.metalworking
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RC plane motor questions
On 06/23/2011 10:10 AM, Robert Roland wrote:
On Thu, 23 Jun 2011 16:18:39 +0000 (UTC), wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. But what kind of signal does the ESC need? The same type of signal that RC servos use? A plain, normal ESC will use the same signal a servo uses. It connects to the receiver just like a servo. There are also special ESCs that are controlled by SPI or similar. These are used where very quick response times are needed. Do I need to get a programming card for the ESC? It depends. Some higher-end ESCs allow you to tune their parameters, but they come preconfigured to working defaults, so will work fine in most applications. Some ESCs are programmed using the throttle stick in connection with beeps emitted through the motor, some need a programming card, while others are connected to a PC. Some controllers cannot be reconfigured at all. And how is the rpm/volt detrermined? It is determined by a number of factors, such as magnet strength, number of windings, number of poles, physical size, and more. I'm thinking that I should get a kit motor to learn about them but I also want to get some regular motors to compare. I've never built my own motor, so I can't help you there. It looks like Hobby King might be the best place to buy the motors from but I don't know. I have not (yet) dealt with them, but I have heard from numerous happy customers, so they seem to be a decent outfit. That's pretty much what I would say. The only exception is that the stuff Hobby King sells can have quality problems, both the kind that causes infant mortality, and issues with long-term reliability and robustness. If you really want it to last, particularly if you're stressing the bearings in any way, Hobby King's products may not be the best. AXI, eFlight, Scorpion, Castle Creations, and Plettenberg are all better (1st tier, or almost so) motor brands that I know. But they're more spendy -- use the Hobby King stuff to get your feet wet, then go from there. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html |
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#7
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RC plane motor questions
On Thu, 23 Jun 2011 13:42:27 -0700, Tim Wescott
wrote: On 06/23/2011 10:10 AM, Robert Roland wrote: On Thu, 23 Jun 2011 16:18:39 +0000 (UTC), wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. But what kind of signal does the ESC need? The same type of signal that RC servos use? A plain, normal ESC will use the same signal a servo uses. It connects to the receiver just like a servo. There are also special ESCs that are controlled by SPI or similar. These are used where very quick response times are needed. Do I need to get a programming card for the ESC? It depends. Some higher-end ESCs allow you to tune their parameters, but they come preconfigured to working defaults, so will work fine in most applications. Some ESCs are programmed using the throttle stick in connection with beeps emitted through the motor, some need a programming card, while others are connected to a PC. Some controllers cannot be reconfigured at all. And how is the rpm/volt detrermined? It is determined by a number of factors, such as magnet strength, number of windings, number of poles, physical size, and more. I'm thinking that I should get a kit motor to learn about them but I also want to get some regular motors to compare. I've never built my own motor, so I can't help you there. It looks like Hobby King might be the best place to buy the motors from but I don't know. I have not (yet) dealt with them, but I have heard from numerous happy customers, so they seem to be a decent outfit. That's pretty much what I would say. The only exception is that the stuff Hobby King sells can have quality problems, both the kind that causes infant mortality, and issues with long-term reliability and robustness. If you really want it to last, particularly if you're stressing the bearings in any way, Hobby King's products may not be the best. AXI, eFlight, Scorpion, Castle Creations, and Plettenberg are all better (1st tier, or almost so) motor brands that I know. But they're more spendy -- use the Hobby King stuff to get your feet wet, then go from there. Thanks Rob, Winston, Cy and Tim, I knew there would be someone here who would be familiar with these things. I have two projects in mind. The first is a gyroscopic stabiliser for a digital camera. I built a prototype with brass flywheels and pager motors. It worked OK but the life of the pager motors is low. And they were a little noisy. So I'm thinking that maybe one of these new fangled three phase brushless motors used with good bearings might work. I seem to remember downloading a circuit built around a 555 timer that puts out the pulses used by servos. So with a cheap ESC, LiPo battery, and brushless motor I might be able to make a lightweight gyro stabiliser. The other project that I've been working on is a spinning wheel with a brake on it. The idea is that when the brake is slowly released the wheel will start to spin, with less braking leading to faster spinning. So I need a motor that can remain stalled without overheating. With a stalled brushed motor the energy delivered is not shared equally by all the windings and so maybe it will overheat. I don't know if the three phase brushless motor drives keep energising windings in sequence when the motor is stalled. This something I want to find out. Eric |
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#8
Posted to rec.crafts.metalworking
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RC plane motor questions
On Jun 23, 3:07*pm, wrote:
On Thu, 23 Jun 2011 13:42:27 -0700, Tim Wescott wrote: On 06/23/2011 10:10 AM, Robert Roland wrote: On Thu, 23 Jun 2011 16:18:39 +0000 (UTC), wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. But what kind of signal does the ESC need? The same type of signal that RC servos use? A plain, normal ESC will use the same signal a servo uses. It connects to the receiver just like a servo. There are also special ESCs that are controlled by SPI or similar. These are used where very quick response times are needed. Do I need to get a programming card for the ESC? It depends. Some higher-end ESCs allow you to tune their parameters, but they come preconfigured to working defaults, so will work fine in most applications. Some ESCs are programmed using the throttle stick in connection with beeps emitted through the motor, some need a programming card, while others are connected to a PC. Some controllers cannot be reconfigured at all. And how is the rpm/volt detrermined? It is determined by a number of factors, such as magnet strength, number of windings, number of poles, physical size, and more. I'm thinking that I should get a kit motor to learn about them but I also want to get some regular motors to compare. I've never built my own motor, so I can't help you there. It looks like Hobby King might be the best place to buy the motors from but I don't know. I have not (yet) dealt with them, but I have heard from numerous happy customers, so they seem to be a decent outfit. That's pretty much what I would say. *The only exception is that the stuff Hobby King sells can have quality problems, both the kind that causes infant mortality, and issues with long-term reliability and robustness. *If you really want it to last, particularly if you're stressing the bearings in any way, Hobby King's products may not be the best. AXI, eFlight, Scorpion, Castle Creations, and Plettenberg are all better (1st tier, or almost so) motor brands that I know. *But they're more spendy -- use the Hobby King stuff to get your feet wet, then go from there. Thanks Rob, Winston, Cy and Tim, I knew there would be someone here who would be familiar with these things. I have two projects in mind. The first is a gyroscopic stabiliser for a digital camera. I built a prototype with brass flywheels and pager motors. It worked OK but the life of the pager motors is low. And they were a little noisy. So I'm thinking that maybe one of these new fangled three phase brushless motors used with good bearings might work. I seem to remember downloading a circuit built around a 555 timer that puts out the pulses used by servos. So with a cheap ESC, LiPo battery, and brushless motor I might be able to make a lightweight gyro stabiliser. The other project that I've been working on is a spinning wheel with a brake on it. The idea is that when the brake is slowly released the wheel will start to spin, with less braking leading to faster spinning. So I need a motor that can remain stalled without overheating. With a stalled brushed motor the energy delivered is not shared equally by all the windings and so maybe it will overheat. I don't know if the three phase brushless motor drives keep energising windings in sequence when the motor is stalled. This something I want to find out. Eric- Hide quoted text - - Show quoted text - How are you dynamically balancing your rotors? Have been looking for a small dynamic balancer that could be built by an individual without bankruptcy staring me in the face. Would be of interest for doing a bunch of projects involving high-speed revolving parts. Think model turbojets... As far as stalled rotors, a friction clutch is the usual solution, motor doesn't see a real current spike that way. Just have to replace the clutch if you wear it out from stalling too frequently. Stan |
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#9
Posted to rec.crafts.metalworking
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RC plane motor questions
"Tim Wescott" wrote in message ... On 06/23/2011 12:48 PM, Cydrome Leader wrote: wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. I'm not sure what you're making, but the power to weight of those brushless motors is quite impressive. There's a catch though, if you're not using them to just run a fan, which is all they're good for. they lack position sensors, so you can't just spin them back and forth like a regular motor unless you have some sort of really awesome motor controller. They seem to now have brushless RC car motors and controllers. I'm not sure how those work though. I believe the brushless car motors have hall sensors for commutation, the same as an industrial servo brushless would. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html The rc car's "electronic speed control" (ESC) support both sensor and sensor less brushless motors. You can program into the handheld transmitter throttle and braking endpoints and curves, linier or otherwise. The speed controlls can deliver lots of power. My Emaxx 1/10 scale rc truck will pull 300 amps acceleration and 180 amps on braking at 16.8 volts. With motors pulling lots of power things can get hot in a hurry. Spektrum transmitter's and receivers are what I prefer. The "2.4Ghz" units eliminate interference and channel crystal changing when near other units. They will automatically switch up to 80 channels/units in the same location. You program failsafe throttle and other servo positions in case of signal loss. Check your local rc racing club. They usually have a web site with help and buy/sell forums |
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#11
Posted to rec.crafts.metalworking
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RC plane motor questions
On Jun 23, 4:42*pm, Tim Wescott wrote:
On 06/23/2011 10:10 AM, Robert Roland wrote: On Thu, 23 Jun 2011 16:18:39 +0000 (UTC), wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm ... That's pretty much what I would say. *The only exception is that the stuff Hobby King sells can have quality problems, both the kind that causes infant mortality, and issues with long-term reliability and robustness. *If you really want it to last, particularly if you're stressing the bearings in any way, Hobby King's products may not be the best. AXI, eFlight, Scorpion, Castle Creations, and Plettenberg are all better (1st tier, or almost so) motor brands that I know. *But they're more spendy -- use the Hobby King stuff to get your feet wet, then go from there. Tim Wescott For serious applications: http://www.maxonmotorusa.com/ jsw |
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#12
Posted to rec.crafts.metalworking
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RC plane motor questions
wrote in message
... I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. But what kind of signal does the ESC need? The same type of signal that RC servos use? Do I need to get a programming card for the ESC? And how is the rpm/volt detrermined? I'm thinking that I should get a kit motor to learn about them but I also want to get some regular motors to compare. It looks like Hobby King might be the best place to buy the motors from but I don't know. Any help would be greatly appreciated. Thanks, Eric R/C sends pulses to the servos or speed controls, they get a pulse about every 20mS or so. The pulse for neutral for a servo, or half speed for an ESC is approximately 1.5mS. The pulse width range is from 1mS to 2mS plus/minus a little fudging on the trim, etc. So, if you want to experiment you can use something like 555 timer IC's or I would suggest something like a Basic Stamp or Arduino. I prefer the Arduino because they are cheaper and much more powerful. I don't know exactly how the R/C brushless motors and speed controls work, they may be something like sensorless vector ac drives. Anyway, I'm not sure exactly but they probably work a lot like 3 phase motors with AC variable speed drives. I think some modern speed controls sense the pulse and automatically program themselves to work properly, the pulse they receive on power up is the OFF and then going the other way increases speed. For example, if they are powered up receiving 1ms pulses, that is off and 2ms pulses would be full throttle. Likewise if they are powered up receiving 2ms pulses then 1ms pulses would be full throttle. Hope this helps RogerN |
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#13
Posted to rec.crafts.metalworking
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RC plane motor questions
wrote in message
... On Thu, 23 Jun 2011 13:42:27 -0700, Tim Wescott wrote: On 06/23/2011 10:10 AM, Robert Roland wrote: On Thu, 23 Jun 2011 16:18:39 +0000 (UTC), wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. But what kind of signal does the ESC need? The same type of signal that RC servos use? A plain, normal ESC will use the same signal a servo uses. It connects to the receiver just like a servo. There are also special ESCs that are controlled by SPI or similar. These are used where very quick response times are needed. Do I need to get a programming card for the ESC? It depends. Some higher-end ESCs allow you to tune their parameters, but they come preconfigured to working defaults, so will work fine in most applications. Some ESCs are programmed using the throttle stick in connection with beeps emitted through the motor, some need a programming card, while others are connected to a PC. Some controllers cannot be reconfigured at all. And how is the rpm/volt detrermined? It is determined by a number of factors, such as magnet strength, number of windings, number of poles, physical size, and more. I'm thinking that I should get a kit motor to learn about them but I also want to get some regular motors to compare. I've never built my own motor, so I can't help you there. It looks like Hobby King might be the best place to buy the motors from but I don't know. I have not (yet) dealt with them, but I have heard from numerous happy customers, so they seem to be a decent outfit. That's pretty much what I would say. The only exception is that the stuff Hobby King sells can have quality problems, both the kind that causes infant mortality, and issues with long-term reliability and robustness. If you really want it to last, particularly if you're stressing the bearings in any way, Hobby King's products may not be the best. AXI, eFlight, Scorpion, Castle Creations, and Plettenberg are all better (1st tier, or almost so) motor brands that I know. But they're more spendy -- use the Hobby King stuff to get your feet wet, then go from there. Thanks Rob, Winston, Cy and Tim, I knew there would be someone here who would be familiar with these things. I have two projects in mind. The first is a gyroscopic stabiliser for a digital camera. I built a prototype with brass flywheels and pager motors. It worked OK but the life of the pager motors is low. And they were a little noisy. So I'm thinking that maybe one of these new fangled three phase brushless motors used with good bearings might work. I seem to remember downloading a circuit built around a 555 timer that puts out the pulses used by servos. So with a cheap ESC, LiPo battery, and brushless motor I might be able to make a lightweight gyro stabiliser. The other project that I've been working on is a spinning wheel with a brake on it. The idea is that when the brake is slowly released the wheel will start to spin, with less braking leading to faster spinning. So I need a motor that can remain stalled without overheating. With a stalled brushed motor the energy delivered is not shared equally by all the windings and so maybe it will overheat. I don't know if the three phase brushless motor drives keep energising windings in sequence when the motor is stalled. This something I want to find out. Eric You might want to check out the gyroscopes used in R/C helicopters to stabilize them, they are real gyroscopes except they use vibration to sense rotation instead of spinning a flywheel. The vibrating crystal resists rotation just like a flywheel or pendulum would, it's called the corollis sp or similar (from memory) effect. These electronic gyros are used in r/c helicopters and also things like the steady-shot in digital cameras. I bought a couple of Murata gyroscopes several years ago but haven't done much with them yet, future project though.... RogerN |
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#14
Posted to rec.crafts.metalworking
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RC plane motor questions
wrote:
On Thu, 23 Jun 2011 13:42:27 -0700, Tim Wescott wrote: On 06/23/2011 10:10 AM, Robert Roland wrote: On Thu, 23 Jun 2011 16:18:39 +0000 (UTC), wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. But what kind of signal does the ESC need? The same type of signal that RC servos use? A plain, normal ESC will use the same signal a servo uses. It connects to the receiver just like a servo. There are also special ESCs that are controlled by SPI or similar. These are used where very quick response times are needed. Do I need to get a programming card for the ESC? It depends. Some higher-end ESCs allow you to tune their parameters, but they come preconfigured to working defaults, so will work fine in most applications. Some ESCs are programmed using the throttle stick in connection with beeps emitted through the motor, some need a programming card, while others are connected to a PC. Some controllers cannot be reconfigured at all. And how is the rpm/volt detrermined? It is determined by a number of factors, such as magnet strength, number of windings, number of poles, physical size, and more. I'm thinking that I should get a kit motor to learn about them but I also want to get some regular motors to compare. I've never built my own motor, so I can't help you there. It looks like Hobby King might be the best place to buy the motors from but I don't know. I have not (yet) dealt with them, but I have heard from numerous happy customers, so they seem to be a decent outfit. That's pretty much what I would say. The only exception is that the stuff Hobby King sells can have quality problems, both the kind that causes infant mortality, and issues with long-term reliability and robustness. If you really want it to last, particularly if you're stressing the bearings in any way, Hobby King's products may not be the best. AXI, eFlight, Scorpion, Castle Creations, and Plettenberg are all better (1st tier, or almost so) motor brands that I know. But they're more spendy -- use the Hobby King stuff to get your feet wet, then go from there. Thanks Rob, Winston, Cy and Tim, I knew there would be someone here who would be familiar with these things. I have two projects in mind. The first is a gyroscopic stabiliser for a digital camera. I built a prototype with brass flywheels and pager motors. It worked OK but the life of the pager motors is low. And they were a little noisy. So I'm thinking that maybe one of these new fangled three phase brushless motors used with good bearings might work. I seem to remember downloading a circuit built around a 555 timer that puts out the pulses used by servos. So with a cheap ESC, LiPo battery, and brushless motor I might be able to make a lightweight gyro stabiliser. The other project that I've been working on is a spinning wheel with a brake on it. The idea is that when the brake is slowly released the wheel will start to spin, with less braking leading to faster spinning. So I need a motor that can remain stalled without overheating. With a stalled brushed motor the energy delivered is not shared equally by all the windings and so maybe it will overheat. I don't know if the three phase brushless motor drives keep energising windings in sequence when the motor is stalled. This something I want to find out. Eric Back in the late 1970s, when living in the US, I saw IIRC mil surplus gyroscopes for stabilising binoculars on sale in some magazine, can't remember which but they may still be around. At the time I was involved in archery and using a 95 lb long bow and took the **** out of the target archers and their pulleys and stabilisers and such and suggested they fit some. It wasn't long after I saw someone doing just that. It was about the same time I realised the mental side of any target sport as shooting at a standard size archery target would result in a given group then placing the likes of a bottle cap in the middle of the target would result in a consistently and significantly smaller group, the smaller target resulting in greater focus. |
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#15
Posted to rec.crafts.metalworking
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RC plane motor questions
On Jun 23, 5:07*pm, wrote:
On Thu, 23 Jun 2011 13:42:27 -0700, Tim Wescott wrote: On 06/23/2011 10:10 AM, Robert Roland wrote: On Thu, 23 Jun 2011 16:18:39 +0000 (UTC), wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. But what kind of signal does the ESC need? The same type of signal that RC servos use? A plain, normal ESC will use the same signal a servo uses. It connects to the receiver just like a servo. There are also special ESCs that are controlled by SPI or similar. These are used where very quick response times are needed. Do I need to get a programming card for the ESC? It depends. Some higher-end ESCs allow you to tune their parameters, but they come preconfigured to working defaults, so will work fine in most applications. Some ESCs are programmed using the throttle stick in connection with beeps emitted through the motor, some need a programming card, while others are connected to a PC. Some controllers cannot be reconfigured at all. And how is the rpm/volt detrermined? It is determined by a number of factors, such as magnet strength, number of windings, number of poles, physical size, and more. I'm thinking that I should get a kit motor to learn about them but I also want to get some regular motors to compare. I've never built my own motor, so I can't help you there. It looks like Hobby King might be the best place to buy the motors from but I don't know. I have not (yet) dealt with them, but I have heard from numerous happy customers, so they seem to be a decent outfit. That's pretty much what I would say. *The only exception is that the stuff Hobby King sells can have quality problems, both the kind that causes infant mortality, and issues with long-term reliability and robustness. *If you really want it to last, particularly if you're stressing the bearings in any way, Hobby King's products may not be the best. AXI, eFlight, Scorpion, Castle Creations, and Plettenberg are all better (1st tier, or almost so) motor brands that I know. *But they're more spendy -- use the Hobby King stuff to get your feet wet, then go from there. Thanks Rob, Winston, Cy and Tim, I knew there would be someone here who would be familiar with these things. I have two projects in mind. The first is a gyroscopic stabiliser for a digital camera. I built a prototype with brass flywheels and pager motors. It worked OK but the life of the pager motors is low. And they were a little noisy. So I'm thinking that maybe one of these new fangled three phase brushless motors used with good bearings might work. I seem to remember downloading a circuit built around a 555 timer that puts out the pulses used by servos. So with a cheap ESC, LiPo battery, and brushless motor I might be able to make a lightweight gyro stabiliser. The other project that I've been working on is a spinning wheel with a brake on it. The idea is that when the brake is slowly released the wheel will start to spin, with less braking leading to faster spinning. So I need a motor that can remain stalled without overheating. With a stalled brushed motor the energy delivered is not shared equally by all the windings and so maybe it will overheat. I don't know if the three phase brushless motor drives keep energising windings in sequence when the motor is stalled. This something I want to find out. Eric- Hide quoted text - - Show quoted text - Instead of screwing around with 555 circuits, you really ought to consider a microcontroller. Making servo pulses with an AVR is super- simple, maybe ten lines of code to get it set up, and from there, you just change a register value to pick a new speed. With one of the AtTiny parts, you'd actueally have fewer components than you would with a 555. |
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#16
Posted to rec.crafts.metalworking
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RC plane motor questions
On Jun 23, 9:34*pm, CaveLamb wrote:
Since Roger is suggesting a roll-yer-own approach I thought I'd offer an example of a software only servo driver. - written for a 16 Mhz AT (way back last century)... ... Back about 1985 I wrote a PC-AT assembly driver for an H bridge motor controller to test open-loop stepper damping schemes for a printer carriage drive. I don't have the code but IIRC it was only 10 - 20 lines, OUT instructions separated by fixed countdown loops to time the pulses. jsw |
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#17
Posted to rec.crafts.metalworking
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RC plane motor questions
On 06/23/2011 02:07 PM, wrote:
On Thu, 23 Jun 2011 13:42:27 -0700, Tim wrote: On 06/23/2011 10:10 AM, Robert Roland wrote: On Thu, 23 Jun 2011 16:18:39 +0000 (UTC), wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. But what kind of signal does the ESC need? The same type of signal that RC servos use? A plain, normal ESC will use the same signal a servo uses. It connects to the receiver just like a servo. There are also special ESCs that are controlled by SPI or similar. These are used where very quick response times are needed. Do I need to get a programming card for the ESC? It depends. Some higher-end ESCs allow you to tune their parameters, but they come preconfigured to working defaults, so will work fine in most applications. Some ESCs are programmed using the throttle stick in connection with beeps emitted through the motor, some need a programming card, while others are connected to a PC. Some controllers cannot be reconfigured at all. And how is the rpm/volt detrermined? It is determined by a number of factors, such as magnet strength, number of windings, number of poles, physical size, and more. I'm thinking that I should get a kit motor to learn about them but I also want to get some regular motors to compare. I've never built my own motor, so I can't help you there. It looks like Hobby King might be the best place to buy the motors from but I don't know. I have not (yet) dealt with them, but I have heard from numerous happy customers, so they seem to be a decent outfit. That's pretty much what I would say. The only exception is that the stuff Hobby King sells can have quality problems, both the kind that causes infant mortality, and issues with long-term reliability and robustness. If you really want it to last, particularly if you're stressing the bearings in any way, Hobby King's products may not be the best. AXI, eFlight, Scorpion, Castle Creations, and Plettenberg are all better (1st tier, or almost so) motor brands that I know. But they're more spendy -- use the Hobby King stuff to get your feet wet, then go from there. Thanks Rob, Winston, Cy and Tim, I knew there would be someone here who would be familiar with these things. I have two projects in mind. The first is a gyroscopic stabiliser for a digital camera. I built a prototype with brass flywheels and pager motors. It worked OK but the life of the pager motors is low. And they were a little noisy. So I'm thinking that maybe one of these new fangled three phase brushless motors used with good bearings might work. I seem to remember downloading a circuit built around a 555 timer that puts out the pulses used by servos. So with a cheap ESC, LiPo battery, and brushless motor I might be able to make a lightweight gyro stabiliser. The other project that I've been working on is a spinning wheel with a brake on it. The idea is that when the brake is slowly released the wheel will start to spin, with less braking leading to faster spinning. So I need a motor that can remain stalled without overheating. With a stalled brushed motor the energy delivered is not shared equally by all the windings and so maybe it will overheat. I don't know if the three phase brushless motor drives keep energising windings in sequence when the motor is stalled. This something I want to find out. Why control motor speed with a brake when you can control it actively? Get an ESC that has a helicopter mode, program it right, and it'll give you a specific RPM at the motor for a specific pulse width at the input. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html |
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#18
Posted to rec.crafts.metalworking
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RC plane motor questions
On 06/23/2011 02:07 PM, wrote:
On Thu, 23 Jun 2011 13:42:27 -0700, Tim wrote: On 06/23/2011 10:10 AM, Robert Roland wrote: On Thu, 23 Jun 2011 16:18:39 +0000 (UTC), wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. But what kind of signal does the ESC need? The same type of signal that RC servos use? A plain, normal ESC will use the same signal a servo uses. It connects to the receiver just like a servo. There are also special ESCs that are controlled by SPI or similar. These are used where very quick response times are needed. Do I need to get a programming card for the ESC? It depends. Some higher-end ESCs allow you to tune their parameters, but they come preconfigured to working defaults, so will work fine in most applications. Some ESCs are programmed using the throttle stick in connection with beeps emitted through the motor, some need a programming card, while others are connected to a PC. Some controllers cannot be reconfigured at all. And how is the rpm/volt detrermined? It is determined by a number of factors, such as magnet strength, number of windings, number of poles, physical size, and more. I'm thinking that I should get a kit motor to learn about them but I also want to get some regular motors to compare. I've never built my own motor, so I can't help you there. It looks like Hobby King might be the best place to buy the motors from but I don't know. I have not (yet) dealt with them, but I have heard from numerous happy customers, so they seem to be a decent outfit. That's pretty much what I would say. The only exception is that the stuff Hobby King sells can have quality problems, both the kind that causes infant mortality, and issues with long-term reliability and robustness. If you really want it to last, particularly if you're stressing the bearings in any way, Hobby King's products may not be the best. AXI, eFlight, Scorpion, Castle Creations, and Plettenberg are all better (1st tier, or almost so) motor brands that I know. But they're more spendy -- use the Hobby King stuff to get your feet wet, then go from there. Thanks Rob, Winston, Cy and Tim, I knew there would be someone here who would be familiar with these things. I have two projects in mind. The first is a gyroscopic stabiliser for a digital camera. I built a prototype with brass flywheels and pager motors. It worked OK but the life of the pager motors is low. And they were a little noisy. So I'm thinking that maybe one of these new fangled three phase brushless motors used with good bearings might work. I seem to remember downloading a circuit built around a 555 timer that puts out the pulses used by servos. So with a cheap ESC, LiPo battery, and brushless motor I might be able to make a lightweight gyro stabiliser. The other project that I've been working on is a spinning wheel with a brake on it. The idea is that when the brake is slowly released the wheel will start to spin, with less braking leading to faster spinning. So I need a motor that can remain stalled without overheating. With a stalled brushed motor the energy delivered is not shared equally by all the windings and so maybe it will overheat. I don't know if the three phase brushless motor drives keep energising windings in sequence when the motor is stalled. This something I want to find out. Note, too, that most ESC's won't just start up and go -- they need to see the command at idle for a while, then they'll recognize a command for a higher speed. This is a safety feature, to keep that great big pair of steak knives you have mounted on the front of your plane from starting to spin if you forgot to set the throttle on your transmitter to idle before you plugged in the battery in the plane. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html |
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#19
Posted to rec.crafts.metalworking
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RC plane motor questions
On Thu, 23 Jun 2011 12:03:01 -0700, Winston
wrote: ...uses a heat sink which only makes contact with a select few of the transistors it is meant to cool: http://home.c2i.net/w-479147/temp/sink.jpg This is a grid of 3 x 5 = 15 transistors with only 7 survivors after a hot run with low batteries. The damage was a result of a malfunction caused by water intrusion. I will add an update to that thread soon. -- RoRo |
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#20
Posted to rec.crafts.metalworking
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RC plane motor questions
On Thu, 23 Jun 2011 18:14:30 -0500, "RogerN"
wrote: I don't know exactly how the R/C brushless motors and speed controls work, they may be something like sensorless vector ac drives. In a sensorless system, the controller measures induced voltage on the non-driven phase of the motor to determine where in the commutation cycle it is. For startup, where the speed is zero and therefore no induced voltage is present, a special startup mode is needed. There are several different techniques for starting up reliably. The simplest method is to just commutate blindly at low speed for a while and see if any voltage appears. This technique will result in limited startup torque, and may even cause the motor to turn backwards a few degrees just as it starts. Anyway, I'm not sure exactly but they probably work a lot like 3 phase motors with AC variable speed drives. Very similar, but they don't use a sine shaped drive. At partial power, the current is modulated, but the frequency and duty cycle remains constant through the whole cycle. At full power, the phase current is either full on or full off. I think some modern speed controls sense the pulse and automatically program themselves to work properly, the pulse they receive on power up is the OFF and then going the other way increases speed. For example, if they are powered up receiving 1ms pulses, that is off and 2ms pulses would be full throttle. Likewise if they are powered up receiving 2ms pulses then 1ms pulses would be full throttle. I have not seen a controller like that. In fact, I think it would be dangerous. The controllers I have seen, will emit beeping noises and refuse to start the motor at all until the operator has lowered the throttle to full stop first. Some controllers enter the configuration mode if they are switched on with the throttle at max. -- RoRo |
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#21
Posted to rec.crafts.metalworking
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RC plane motor questions
john B. wrote:
Well, anyway, presented here just to dig the C-hags...  A real programmer would use binary :-) Not since John Von Neumann met the ENIAC... -- Richard Lamb http://www.home.earthlink.net/~cavelamb http://www.home.earthlink.net/~sv_temptress |
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#22
Posted to rec.crafts.metalworking
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RC plane motor questions
On Jun 24, 7:49*am, john B. wrote:
On Thu, 23 Jun 2011 20:34:23 -0500, CaveLamb wrote: ... A real programmer would use binary :-) ... Then I was a "real" programmer until I got tired of flipping switches and wired in an octal keypad. You would have posted in Morse from your home-built ham station. ..--- ... .-- |
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#23
Posted to rec.crafts.metalworking
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RC plane motor questions
On Thu, 23 Jun 2011 18:27:22 -0500, "RogerN"
wrote: wrote in message .. . On Thu, 23 Jun 2011 13:42:27 -0700, Tim Wescott wrote: On 06/23/2011 10:10 AM, Robert Roland wrote: On Thu, 23 Jun 2011 16:18:39 +0000 (UTC), wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. But what kind of signal does the ESC need? The same type of signal that RC servos use? A plain, normal ESC will use the same signal a servo uses. It connects to the receiver just like a servo. There are also special ESCs that are controlled by SPI or similar. These are used where very quick response times are needed. Do I need to get a programming card for the ESC? It depends. Some higher-end ESCs allow you to tune their parameters, but they come preconfigured to working defaults, so will work fine in most applications. Some ESCs are programmed using the throttle stick in connection with beeps emitted through the motor, some need a programming card, while others are connected to a PC. Some controllers cannot be reconfigured at all. And how is the rpm/volt detrermined? It is determined by a number of factors, such as magnet strength, number of windings, number of poles, physical size, and more. I'm thinking that I should get a kit motor to learn about them but I also want to get some regular motors to compare. I've never built my own motor, so I can't help you there. It looks like Hobby King might be the best place to buy the motors from but I don't know. I have not (yet) dealt with them, but I have heard from numerous happy customers, so they seem to be a decent outfit. That's pretty much what I would say. The only exception is that the stuff Hobby King sells can have quality problems, both the kind that causes infant mortality, and issues with long-term reliability and robustness. If you really want it to last, particularly if you're stressing the bearings in any way, Hobby King's products may not be the best. AXI, eFlight, Scorpion, Castle Creations, and Plettenberg are all better (1st tier, or almost so) motor brands that I know. But they're more spendy -- use the Hobby King stuff to get your feet wet, then go from there. Thanks Rob, Winston, Cy and Tim, I knew there would be someone here who would be familiar with these things. I have two projects in mind. The first is a gyroscopic stabiliser for a digital camera. I built a prototype with brass flywheels and pager motors. It worked OK but the life of the pager motors is low. And they were a little noisy. So I'm thinking that maybe one of these new fangled three phase brushless motors used with good bearings might work. I seem to remember downloading a circuit built around a 555 timer that puts out the pulses used by servos. So with a cheap ESC, LiPo battery, and brushless motor I might be able to make a lightweight gyro stabiliser. The other project that I've been working on is a spinning wheel with a brake on it. The idea is that when the brake is slowly released the wheel will start to spin, with less braking leading to faster spinning. So I need a motor that can remain stalled without overheating. With a stalled brushed motor the energy delivered is not shared equally by all the windings and so maybe it will overheat. I don't know if the three phase brushless motor drives keep energising windings in sequence when the motor is stalled. This something I want to find out. Eric You might want to check out the gyroscopes used in R/C helicopters to stabilize them, they are real gyroscopes except they use vibration to sense rotation instead of spinning a flywheel. The vibrating crystal resists rotation just like a flywheel or pendulum would, it's called the corollis sp or similar (from memory) effect. These electronic gyros are used in r/c helicopters and also things like the steady-shot in digital cameras. I bought a couple of Murata gyroscopes several years ago but haven't done much with them yet, future project though.... RogerN The purpose of my gyros is to do the actual stabilising. The gyros used in helicopters are sensors. In my Sony camera is some type of physical lens positioning system that uses some type of motion sensor for positioning info. However, it is not enough for more violent shaking. I have a relative who loves to take pictures but has hands that now shake so much that some type of stabiliser might really help. Eric |
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#24
Posted to rec.crafts.metalworking
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RC plane motor questions
On Thu, 23 Jun 2011 18:12:31 -0700 (PDT), rangerssuck
wrote: On Jun 23, 5:07*pm, wrote: On Thu, 23 Jun 2011 13:42:27 -0700, Tim Wescott wrote: On 06/23/2011 10:10 AM, Robert Roland wrote: On Thu, 23 Jun 2011 16:18:39 +0000 (UTC), wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. But what kind of signal does the ESC need? The same type of signal that RC servos use? A plain, normal ESC will use the same signal a servo uses. It connects to the receiver just like a servo. There are also special ESCs that are controlled by SPI or similar. These are used where very quick response times are needed. Do I need to get a programming card for the ESC? It depends. Some higher-end ESCs allow you to tune their parameters, but they come preconfigured to working defaults, so will work fine in most applications. Some ESCs are programmed using the throttle stick in connection with beeps emitted through the motor, some need a programming card, while others are connected to a PC. Some controllers cannot be reconfigured at all. And how is the rpm/volt detrermined? It is determined by a number of factors, such as magnet strength, number of windings, number of poles, physical size, and more. I'm thinking that I should get a kit motor to learn about them but I also want to get some regular motors to compare. I've never built my own motor, so I can't help you there. It looks like Hobby King might be the best place to buy the motors from but I don't know. I have not (yet) dealt with them, but I have heard from numerous happy customers, so they seem to be a decent outfit. That's pretty much what I would say. *The only exception is that the stuff Hobby King sells can have quality problems, both the kind that causes infant mortality, and issues with long-term reliability and robustness. *If you really want it to last, particularly if you're stressing the bearings in any way, Hobby King's products may not be the best. AXI, eFlight, Scorpion, Castle Creations, and Plettenberg are all better (1st tier, or almost so) motor brands that I know. *But they're more spendy -- use the Hobby King stuff to get your feet wet, then go from there. Thanks Rob, Winston, Cy and Tim, I knew there would be someone here who would be familiar with these things. I have two projects in mind. The first is a gyroscopic stabiliser for a digital camera. I built a prototype with brass flywheels and pager motors. It worked OK but the life of the pager motors is low. And they were a little noisy. So I'm thinking that maybe one of these new fangled three phase brushless motors used with good bearings might work. I seem to remember downloading a circuit built around a 555 timer that puts out the pulses used by servos. So with a cheap ESC, LiPo battery, and brushless motor I might be able to make a lightweight gyro stabiliser. The other project that I've been working on is a spinning wheel with a brake on it. The idea is that when the brake is slowly released the wheel will start to spin, with less braking leading to faster spinning. So I need a motor that can remain stalled without overheating. With a stalled brushed motor the energy delivered is not shared equally by all the windings and so maybe it will overheat. I don't know if the three phase brushless motor drives keep energising windings in sequence when the motor is stalled. This something I want to find out. Eric- Hide quoted text - - Show quoted text - Instead of screwing around with 555 circuits, you really ought to consider a microcontroller. Making servo pulses with an AVR is super- simple, maybe ten lines of code to get it set up, and from there, you just change a register value to pick a new speed. With one of the AtTiny parts, you'd actueally have fewer components than you would with a 555. I know how to control a servo with a microcontoller. The 555 solution is, I believe, cheaper. Eric |
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#25
Posted to rec.crafts.metalworking
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RC plane motor questions
On Jun 24, 11:40*am, wrote:
On Thu, 23 Jun 2011 18:12:31 -0700 (PDT), rangerssuck wrote: On Jun 23, 5:07*pm, wrote: On Thu, 23 Jun 2011 13:42:27 -0700, Tim Wescott wrote: On 06/23/2011 10:10 AM, Robert Roland wrote: On Thu, 23 Jun 2011 16:18:39 +0000 (UTC), wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. But what kind of signal does the ESC need? The same type of signal that RC servos use? A plain, normal ESC will use the same signal a servo uses. It connects to the receiver just like a servo. There are also special ESCs that are controlled by SPI or similar. These are used where very quick response times are needed. Do I need to get a programming card for the ESC? It depends. Some higher-end ESCs allow you to tune their parameters, but they come preconfigured to working defaults, so will work fine in most applications. Some ESCs are programmed using the throttle stick in connection with beeps emitted through the motor, some need a programming card, while others are connected to a PC. Some controllers cannot be reconfigured at all. And how is the rpm/volt detrermined? It is determined by a number of factors, such as magnet strength, number of windings, number of poles, physical size, and more. I'm thinking that I should get a kit motor to learn about them but I also want to get some regular motors to compare. I've never built my own motor, so I can't help you there. It looks like Hobby King might be the best place to buy the motors from but I don't know. I have not (yet) dealt with them, but I have heard from numerous happy customers, so they seem to be a decent outfit. That's pretty much what I would say. *The only exception is that the stuff Hobby King sells can have quality problems, both the kind that causes infant mortality, and issues with long-term reliability and robustness. *If you really want it to last, particularly if you're stressing the bearings in any way, Hobby King's products may not be the best. AXI, eFlight, Scorpion, Castle Creations, and Plettenberg are all better (1st tier, or almost so) motor brands that I know. *But they're more spendy -- use the Hobby King stuff to get your feet wet, then go from there. Thanks Rob, Winston, Cy and Tim, I knew there would be someone here who would be familiar with these things. I have two projects in mind. The first is a gyroscopic stabiliser for a digital camera. I built a prototype with brass flywheels and pager motors. It worked OK but the life of the pager motors is low. And they were a little noisy. So I'm thinking that maybe one of these new fangled three phase brushless motors used with good bearings might work. I seem to remember downloading a circuit built around a 555 timer that puts out the pulses used by servos. So with a cheap ESC, LiPo battery, and brushless motor I might be able to make a lightweight gyro stabiliser. The other project that I've been working on is a spinning wheel with a brake on it. The idea is that when the brake is slowly released the wheel will start to spin, with less braking leading to faster spinning. So I need a motor that can remain stalled without overheating. With a stalled brushed motor the energy delivered is not shared equally by all the windings and so maybe it will overheat. I don't know if the three phase brushless motor drives keep energising windings in sequence when the motor is stalled. This something I want to find out. Eric- Hide quoted text - - Show quoted text - Instead of screwing around with 555 circuits, you really ought to consider a microcontroller. Making servo pulses with an AVR is super- simple, maybe ten lines of code to get it set up, and from there, you just change a register value to pick a new speed. With one of the AtTiny parts, you'd actueally have fewer components than you would with a 555. I know how to control a servo with a microcontoller. The 555 solution is, I believe, cheaper. Eric- Hide quoted text - - Show quoted text - maybe, but not by more than a buck or so. |
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#26
Posted to rec.crafts.metalworking
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RC plane motor questions
On Thu, 23 Jun 2011 23:07:32 -0700, Tim Wescott
wrote: On 06/23/2011 02:07 PM, wrote: On Thu, 23 Jun 2011 13:42:27 -0700, Tim wrote: On 06/23/2011 10:10 AM, Robert Roland wrote: On Thu, 23 Jun 2011 16:18:39 +0000 (UTC), wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. But what kind of signal does the ESC need? The same type of signal that RC servos use? A plain, normal ESC will use the same signal a servo uses. It connects to the receiver just like a servo. There are also special ESCs that are controlled by SPI or similar. These are used where very quick response times are needed. Do I need to get a programming card for the ESC? It depends. Some higher-end ESCs allow you to tune their parameters, but they come preconfigured to working defaults, so will work fine in most applications. Some ESCs are programmed using the throttle stick in connection with beeps emitted through the motor, some need a programming card, while others are connected to a PC. Some controllers cannot be reconfigured at all. And how is the rpm/volt detrermined? It is determined by a number of factors, such as magnet strength, number of windings, number of poles, physical size, and more. I'm thinking that I should get a kit motor to learn about them but I also want to get some regular motors to compare. I've never built my own motor, so I can't help you there. It looks like Hobby King might be the best place to buy the motors from but I don't know. I have not (yet) dealt with them, but I have heard from numerous happy customers, so they seem to be a decent outfit. That's pretty much what I would say. The only exception is that the stuff Hobby King sells can have quality problems, both the kind that causes infant mortality, and issues with long-term reliability and robustness. If you really want it to last, particularly if you're stressing the bearings in any way, Hobby King's products may not be the best. AXI, eFlight, Scorpion, Castle Creations, and Plettenberg are all better (1st tier, or almost so) motor brands that I know. But they're more spendy -- use the Hobby King stuff to get your feet wet, then go from there. Thanks Rob, Winston, Cy and Tim, I knew there would be someone here who would be familiar with these things. I have two projects in mind. The first is a gyroscopic stabiliser for a digital camera. I built a prototype with brass flywheels and pager motors. It worked OK but the life of the pager motors is low. And they were a little noisy. So I'm thinking that maybe one of these new fangled three phase brushless motors used with good bearings might work. I seem to remember downloading a circuit built around a 555 timer that puts out the pulses used by servos. So with a cheap ESC, LiPo battery, and brushless motor I might be able to make a lightweight gyro stabiliser. The other project that I've been working on is a spinning wheel with a brake on it. The idea is that when the brake is slowly released the wheel will start to spin, with less braking leading to faster spinning. So I need a motor that can remain stalled without overheating. With a stalled brushed motor the energy delivered is not shared equally by all the windings and so maybe it will overheat. I don't know if the three phase brushless motor drives keep energising windings in sequence when the motor is stalled. This something I want to find out. Note, too, that most ESC's won't just start up and go -- they need to see the command at idle for a while, then they'll recognize a command for a higher speed. This is a safety feature, to keep that great big pair of steak knives you have mounted on the front of your plane from starting to spin if you forgot to set the throttle on your transmitter to idle before you plugged in the battery in the plane. Thanks for the starting advive Tim. As for controlling speed, it's not the brake that's controlling the speed. The motor will need to spin at some determined speed but the driven wheel will sometimes be subjected braking forces and when these forces diminish the wheel must resume the determined speed smoothly. Thanks, Eric |
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#27
Posted to rec.crafts.metalworking
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RC plane motor questions
On Fri, 24 Jun 2011 09:18:41 -0700 (PDT), rangerssuck
wrote: On Jun 24, 11:40*am, wrote: On Thu, 23 Jun 2011 18:12:31 -0700 (PDT), rangerssuck wrote: On Jun 23, 5:07*pm, wrote: On Thu, 23 Jun 2011 13:42:27 -0700, Tim Wescott wrote: On 06/23/2011 10:10 AM, Robert Roland wrote: On Thu, 23 Jun 2011 16:18:39 +0000 (UTC), wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. But what kind of signal does the ESC need? The same type of signal that RC servos use? A plain, normal ESC will use the same signal a servo uses. It connects to the receiver just like a servo. There are also special ESCs that are controlled by SPI or similar. These are used where very quick response times are needed. Do I need to get a programming card for the ESC? It depends. Some higher-end ESCs allow you to tune their parameters, but they come preconfigured to working defaults, so will work fine in most applications. Some ESCs are programmed using the throttle stick in connection with beeps emitted through the motor, some need a programming card, while others are connected to a PC. Some controllers cannot be reconfigured at all. And how is the rpm/volt detrermined? It is determined by a number of factors, such as magnet strength, number of windings, number of poles, physical size, and more. I'm thinking that I should get a kit motor to learn about them but I also want to get some regular motors to compare. I've never built my own motor, so I can't help you there. It looks like Hobby King might be the best place to buy the motors from but I don't know. I have not (yet) dealt with them, but I have heard from numerous happy customers, so they seem to be a decent outfit. That's pretty much what I would say. *The only exception is that the stuff Hobby King sells can have quality problems, both the kind that causes infant mortality, and issues with long-term reliability and robustness. *If you really want it to last, particularly if you're stressing the bearings in any way, Hobby King's products may not be the best. AXI, eFlight, Scorpion, Castle Creations, and Plettenberg are all better (1st tier, or almost so) motor brands that I know. *But they're more spendy -- use the Hobby King stuff to get your feet wet, then go from there. Thanks Rob, Winston, Cy and Tim, I knew there would be someone here who would be familiar with these things. I have two projects in mind. The first is a gyroscopic stabiliser for a digital camera. I built a prototype with brass flywheels and pager motors. It worked OK but the life of the pager motors is low. And they were a little noisy. So I'm thinking that maybe one of these new fangled three phase brushless motors used with good bearings might work. I seem to remember downloading a circuit built around a 555 timer that puts out the pulses used by servos. So with a cheap ESC, LiPo battery, and brushless motor I might be able to make a lightweight gyro stabiliser. The other project that I've been working on is a spinning wheel with a brake on it. The idea is that when the brake is slowly released the wheel will start to spin, with less braking leading to faster spinning. So I need a motor that can remain stalled without overheating. With a stalled brushed motor the energy delivered is not shared equally by all the windings and so maybe it will overheat. I don't know if the three phase brushless motor drives keep energising windings in sequence when the motor is stalled. This something I want to find out. Eric- Hide quoted text - - Show quoted text - Instead of screwing around with 555 circuits, you really ought to consider a microcontroller. Making servo pulses with an AVR is super- simple, maybe ten lines of code to get it set up, and from there, you just change a register value to pick a new speed. With one of the AtTiny parts, you'd actueally have fewer components than you would with a 555. I know how to control a servo with a microcontoller. The 555 solution is, I believe, cheaper. Eric- Hide quoted text - - Show quoted text - maybe, but not by more than a buck or so. I bought a Basic Stamp kit from Parallax and learned how to control servos with a microcontroller. I'm not sure how use a pot to vary the pulse output rate from the stamp. But I can do this easily with a 555. If I needed hundreds of motor drivers I wonder what would be the best way to go. If I just wanted to control no load speed and direction without any type of feedback from the motor could a microcontroller do that by using power transistors? Easily and cheaply? Since I haven't even ordered a motor and ESC yet these questions may be premature. Eric |
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RC plane motor questions
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#29
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RC plane motor questions
Robert Roland wrote:
On Fri, 24 Jun 2011 19:08:45 +0000 (UTC), wrote: If I just wanted to control no load speed and direction without any type of feedback from the motor could a microcontroller do that by using power transistors? Easily and cheaply? These motors cannot practically be driven without feedback, but you could very well use the micro to handle the feedback as well. In fact, all the commercial ESCs I have seen close up use not much more than an Atmel microcontroller and a bunch of power MOSFETs to do the job. If you had access to the firmware, you could simply modify it to read a potentiometer directly in stead of reading the pulses from the RC receiver. If you want to build your own, you can find several open designs where both hardware drawings and source code is freely available. Why bother with a pot? Actually, there are several solid state 3-axis accelerometers available. Parallax has one - pretty reasonably priced. -- Richard Lamb http://www.home.earthlink.net/~cavelamb http://www.home.earthlink.net/~sv_temptress |
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#30
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RC plane motor questions
"Robert Roland" wrote in message
... On Thu, 23 Jun 2011 18:14:30 -0500, "RogerN" wrote: I don't know exactly how the R/C brushless motors and speed controls work, they may be something like sensorless vector ac drives. In a sensorless system, the controller measures induced voltage on the non-driven phase of the motor to determine where in the commutation cycle it is. For startup, where the speed is zero and therefore no induced voltage is present, a special startup mode is needed. There are several different techniques for starting up reliably. The simplest method is to just commutate blindly at low speed for a while and see if any voltage appears. This technique will result in limited startup torque, and may even cause the motor to turn backwards a few degrees just as it starts. Anyway, I'm not sure exactly but they probably work a lot like 3 phase motors with AC variable speed drives. Very similar, but they don't use a sine shaped drive. At partial power, the current is modulated, but the frequency and duty cycle remains constant through the whole cycle. At full power, the phase current is either full on or full off. I think some modern speed controls sense the pulse and automatically program themselves to work properly, the pulse they receive on power up is the OFF and then going the other way increases speed. For example, if they are powered up receiving 1ms pulses, that is off and 2ms pulses would be full throttle. Likewise if they are powered up receiving 2ms pulses then 1ms pulses would be full throttle. I have not seen a controller like that. In fact, I think it would be dangerous. The controllers I have seen, will emit beeping noises and refuse to start the motor at all until the operator has lowered the throttle to full stop first. Some controllers enter the configuration mode if they are switched on with the throttle at max. -- RoRo Yeah, that's right, I was getting confused between my car speed controls and heli speed controls. The car reversible speed control automatically sets the zero speed on power up, this is because some transmitters have 50/50 forward reverse, some have 70/30 or somewhere around there. The heli speed controls start flashing and disable if they are above zero throttle. I haven't measured the pulse width connected to a speed control so I don't know if zero speed is 1ms or 2ms pulse. One of my heli speed controls has a governor, that might be nice for gyroscopes. RogerN |
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#31
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RC plane motor questions
On Fri, 24 Jun 2011 07:43:13 -0500, CaveLamb
wrote: john B. wrote: Well, anyway, presented here just to dig the C-hags... A real programmer would use binary :-) Not since John Von Neumann met the ENIAC... I actually met a bloke that had worked on computers where to boot you had to enter a small "read that and do something about it" routine on the front panel. |
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#32
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RC plane motor questions
wrote:
On Thu, 23 Jun 2011 13:42:27 -0700, Tim Wescott wrote: On 06/23/2011 10:10 AM, Robert Roland wrote: On Thu, 23 Jun 2011 16:18:39 +0000 (UTC), wrote: I've been interested in small brushless motors for some time and it seems like the ones made for RC use are plentiful and cheap. Bujt I'm having a hard time getting my questions answered about these things. My uses will not be in some type of RC toy, but "toys" that I want to make for myself. I know I will need to get an ESC to drive the motor. But what kind of signal does the ESC need? The same type of signal that RC servos use? A plain, normal ESC will use the same signal a servo uses. It connects to the receiver just like a servo. There are also special ESCs that are controlled by SPI or similar. These are used where very quick response times are needed. Do I need to get a programming card for the ESC? It depends. Some higher-end ESCs allow you to tune their parameters, but they come preconfigured to working defaults, so will work fine in most applications. Some ESCs are programmed using the throttle stick in connection with beeps emitted through the motor, some need a programming card, while others are connected to a PC. Some controllers cannot be reconfigured at all. And how is the rpm/volt detrermined? It is determined by a number of factors, such as magnet strength, number of windings, number of poles, physical size, and more. I'm thinking that I should get a kit motor to learn about them but I also want to get some regular motors to compare. I've never built my own motor, so I can't help you there. It looks like Hobby King might be the best place to buy the motors from but I don't know. I have not (yet) dealt with them, but I have heard from numerous happy customers, so they seem to be a decent outfit. That's pretty much what I would say. The only exception is that the stuff Hobby King sells can have quality problems, both the kind that causes infant mortality, and issues with long-term reliability and robustness. If you really want it to last, particularly if you're stressing the bearings in any way, Hobby King's products may not be the best. AXI, eFlight, Scorpion, Castle Creations, and Plettenberg are all better (1st tier, or almost so) motor brands that I know. But they're more spendy -- use the Hobby King stuff to get your feet wet, then go from there. Thanks Rob, Winston, Cy and Tim, I knew there would be someone here who would be familiar with these things. I have two projects in mind. The first is a gyroscopic stabiliser for a digital camera. I built a prototype with brass flywheels and pager motors. It worked OK but the life of the pager motors is low. And they were a little noisy. So I'm thinking that maybe one of these new fangled three phase brushless motors used with good bearings might work. I seem to remember downloading a circuit If you're getting by with pagers motors, I think these RC type motors are probalby way too big for what you need. astroflight.com does have some smaller motors these days. maxcim.com has some of the largest ones. for precision tiny motors, check out http://www.portescap.com/ You can't even hear some of those motors when they're running. pancake type motors can be used AS flywheels too- try to get a motor from a DLT tape drive. they're really nice. built around a 555 timer that puts out the pulses used by servos. So with a cheap ESC, LiPo battery, and brushless motor I might be able to make a lightweight gyro stabiliser. The other project that I've been working on is a spinning wheel with a brake on it. The idea is that when the brake is slowly released the wheel will start to spin, with less braking leading to faster spinning. So I need a motor that can remain stalled without overheating. With a stalled brushed motor the energy delivered is not shared equally by all the windings and so maybe it will overheat. I don't know if the three phase brushless motor drives keep energising windings in sequence when the motor is stalled. This something I want to find out. Eric Maybe you can make some sort of magnetic coupling as used in pumps. In brushless motor fans, they have what's called "locked rotor protection". If the motor stalls, the driver circuit pretty much gives up and doesn't output full power, waits a second or two and tries to start the fan again to see if the fault clears. They usually do this forever without burning out. Some induction motors are "impedance protected" and won't burn out if stalled as their impedance is high enough that they can't draw enough power to burst into flames in the first place. |
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#33
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RC plane motor questions
On Jun 24, 9:46*pm, john B. wrote:
... I actually met a bloke that had worked on computers where to boot you had to enter a small "read that and do something about it" routine on the front panel. I'm a bloke who designed and built one. The manually entered bootstrap loader was a 32 byte loop that read in a Teletype tape, downwards so the final byte overwrote a jump destination to start the monitor program, which was a very simple operating system that could load more code from paper or magnetic tape. IIRC the bootstrap loader began with a conditional jump to the monitor that wasn't true at cold start. The paper tape boot program changed it to JMP to skip the bootstrap loader at subsequent resets. jsw |
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#34
Posted to rec.crafts.metalworking
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RC plane motor questions
Jim Wilkins wrote:
On Jun 24, 9:46 pm, john wrote: ... I actually met a bloke that had worked on computers where to boot you had to enter a small "read that and do something about it" routine on the front panel. I'm a bloke who designed and built one. The manually entered bootstrap loader was a 32 byte loop that read in a Teletype tape, downwards so the final byte overwrote a jump destination to start the monitor program, which was a very simple operating system that could load more code from paper or magnetic tape. IIRC the bootstrap loader began with a conditional jump to the monitor that wasn't true at cold start. The paper tape boot program changed it to JMP to skip the bootstrap loader at subsequent resets. jsw The Okuma OSP-2000 cnc control loaded with boot strap loader loop. You first have to manually set in about 21 bytes of code using switches to set up the computer to run the bootstrap from a short punch tape. Once you load the bootstrap the actual executive system tapes can be loaded. These machines used two 8K bubble memory boards. The newer options went with a cmos memory. John |
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