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#1
Posted to alt.electronics
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Power Requirements
Made several PCBs (digitally) and now looking at what power I'll need to
power them. Pretty simple boards, bunch of LEDs, resistors for those LEDs, relays, and switches. As I said, pretty simple. :-) I need to decide on voltage as well as the amperage requirement. This is my first project I've done entirely by myself so just looking for ideas. Do I need to add up the amperage requirement for each LED? (.020mA) and then the requirement for each Relay and then thats my requirement? Does this need to be done for the voltage? If each LED is 2VDC and .020mA and I have 10 does that mean I need 20VDC at .200mA or just 2VDC at .200mA? There is no amperage requirement for resistors, correct? Also the current will be flowing through 100feet of cable, I'm assuming I need to figure in resistance at that kind of length? Thanks for any help! |
#2
Posted to alt.electronics
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Power Requirements
On Thu, 14 Dec 2006 00:32:29 GMT, "SBFan2000"
wrote: Made several PCBs (digitally) and now looking at what power I'll need to power them. Pretty simple boards, bunch of LEDs, resistors for those LEDs, relays, and switches. As I said, pretty simple. :-) I need to decide on voltage as well as the amperage requirement. This is my first project I've done entirely by myself so just looking for ideas. Do I need to add up the amperage requirement for each LED? (.020mA) and then the requirement for each Relay and then thats my requirement? Does this need to be done for the voltage? If each LED is 2VDC and .020mA and I have 10 does that mean I need 20VDC at .200mA or just 2VDC at .200mA? There is no amperage requirement for resistors, correct? Also the current will be flowing through 100feet of cable, I'm assuming I need to figure in resistance at that kind of length? Thanks for any help! I don't want to decry your efforts concerning your venture with making your first pcb's but I make the observation that you seem to have tackled this back to front :-) When designing a pcb it is generally known beforehand what the circuit design will be and what components will be used. Only with this knowledge beforehand can you determine the component layout and what thickness and spacing requirements are for the copper tracks. Each pcb you design will be specific to the design project, except in the case you are producing a general purpose bredboarding type pcb. Usually, one doesn't make breadboarding pcb's these days except for special cases and in most cases using a protoboard is the way to go to settle on a final design. Only when the design is finalised do you design the pcb. Having said that, your brief description requiring driving of leds, relays and switches will be dependant upon the pcb layout. For example, if you have laid out the pcb so that the leds are in series then the voltage requirement to drive them will be higher than if you have arranged the leds to be driven in parallel. Also, depending upon the led colour, the voltage requirements will be different for each led colour. Then if you use high efficiency leds these require no more than 5mA for operation. If you get my drift, what I am saying is do things the right order - circuit design, prototype construction, pcb design, first-final build in that order. (In many cases the first-final build - as implied - will not be the last, except for the simplest designs. Good luck with your project. |
#3
Posted to alt.electronics
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Power Requirements
I did pick out final components except for the relays. I'm not entirely
understanding how they are rated. I left room on the PCBs to accomidate most relays pins. I had a good idea of the voltage I wanted to use. I had selected 24vdc but was wondering if 12 or 18vdc would be enough. Basically I want a button that I push on a "control panel" to travel the 100ft to a relay which then turns on a 115vac supply. Like I said I'm having issues understanding the way relays are rated. Assuming I go with 24vdc I would need a relay with a coil rated at 24vdc and a N.O. switch that can handle 115vac at 10-20A, correct? All leds are either red or green and based on what I read are 2vdc at ..020mA. I do have 3-4 blue leds which I read at 4vdc and .040mA (if memory serves) Could you explain "in series" and "in Parallel." The way I understand it (and I could be wrong) Parallel would be having power go from one led to the other in a chain? Serial would be a home run track, back to power, for each led. In this case parallel is the way I did it. (with a resistor for each led) I didn't mean to imply that the PCBs are totally done. They are merely to the point where I can no longer put off relay selection. That all said, I don't doubt I'm doing things wrong and backwards, it is my first PCB from scratch. (I've repaired them at work) How about these: http://cgi.ebay.com/Tyco-Relays-SPST...QQcmdZViewItem "Ross Herbert" wrote in message ... On Thu, 14 Dec 2006 00:32:29 GMT, "SBFan2000" wrote: Made several PCBs (digitally) and now looking at what power I'll need to power them. Pretty simple boards, bunch of LEDs, resistors for those LEDs, relays, and switches. As I said, pretty simple. :-) I need to decide on voltage as well as the amperage requirement. This is my first project I've done entirely by myself so just looking for ideas. Do I need to add up the amperage requirement for each LED? (.020mA) and then the requirement for each Relay and then thats my requirement? Does this need to be done for the voltage? If each LED is 2VDC and .020mA and I have 10 does that mean I need 20VDC at .200mA or just 2VDC at .200mA? There is no amperage requirement for resistors, correct? Also the current will be flowing through 100feet of cable, I'm assuming I need to figure in resistance at that kind of length? Thanks for any help! I don't want to decry your efforts concerning your venture with making your first pcb's but I make the observation that you seem to have tackled this back to front :-) When designing a pcb it is generally known beforehand what the circuit design will be and what components will be used. Only with this knowledge beforehand can you determine the component layout and what thickness and spacing requirements are for the copper tracks. Each pcb you design will be specific to the design project, except in the case you are producing a general purpose bredboarding type pcb. Usually, one doesn't make breadboarding pcb's these days except for special cases and in most cases using a protoboard is the way to go to settle on a final design. Only when the design is finalised do you design the pcb. Having said that, your brief description requiring driving of leds, relays and switches will be dependant upon the pcb layout. For example, if you have laid out the pcb so that the leds are in series then the voltage requirement to drive them will be higher than if you have arranged the leds to be driven in parallel. Also, depending upon the led colour, the voltage requirements will be different for each led colour. Then if you use high efficiency leds these require no more than 5mA for operation. If you get my drift, what I am saying is do things the right order - circuit design, prototype construction, pcb design, first-final build in that order. (In many cases the first-final build - as implied - will not be the last, except for the simplest designs. Good luck with your project. |
#4
Posted to alt.electronics
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Power Requirements
On Thu, 14 Dec 2006 02:02:22 GMT, "SBFan2000"
wrote: I did pick out final components except for the relays. I'm not entirely understanding how they are rated. I left room on the PCBs to accomidate most relays pins. I had a good idea of the voltage I wanted to use. I had selected 24vdc but was wondering if 12 or 18vdc would be enough. Basically I want a button that I push on a "control panel" to travel the 100ft to a relay which then turns on a 115vac supply. Like I said I'm having issues understanding the way relays are rated. Assuming I go with 24vdc I would need a relay with a coil rated at 24vdc and a N.O. switch that can handle 115vac at 10-20A, correct? You could use any voltage you like depending upon what guage wire you use for the 100ft link. Generally any voltage from 12V - 24V would be quite suitable if you use twin conductor cable with conductors of 0.4mm (26AWG) diameter (or better) copper. All leds are either red or green and based on what I read are 2vdc at .020mA. I do have 3-4 blue leds which I read at 4vdc and .040mA (if memory serves) Could you explain "in series" and "in Parallel." The way I understand it (and I could be wrong) Parallel would be having power go from one led to the other in a chain? Serial would be a home run track, back to power, for each led. In this case parallel is the way I did it. (with a resistor for each led) Oh dear me.... are you sure you should be getting into a project involving 115Vac? If you don't understand what series and parallel connections for low voltage components such as leds then you could get yourself killed when playing around with lethal voltages and currents. Have you tried doing some basic research into the meaning of these terms? - Google is your friend... I would never connect leds of different colours in a series string because they all have different voltage requirements. I would only connect leds of the same colour in any individual series string. I didn't mean to imply that the PCBs are totally done. They are merely to the point where I can no longer put off relay selection. That all said, I don't doubt I'm doing things wrong and backwards, it is my first PCB from scratch. (I've repaired them at work) How about these: http://cgi.ebay.com/Tyco-Relays-SPST...QQcmdZViewItem It depends on what type of load you are planning to control with the relay output. That particular relay is only rated to switch 10A @ 250Vac into a resistive load. Also, it can only switch a maximum load of 280W. You would not use it to control an inductive load such as a 115Vac electric motor or pump. See full data sheet here http://relays.tycoelectronics.com/datasheets/OJ-OJE.pdf What type of load are you intending to drive? |
#5
Posted to alt.electronics
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Power Requirements
"Ross Herbert" wrote in message ... On Thu, 14 Dec 2006 02:02:22 GMT, "SBFan2000" wrote: I did pick out final components except for the relays. I'm not entirely understanding how they are rated. I left room on the PCBs to accomidate most relays pins. I had a good idea of the voltage I wanted to use. I had selected 24vdc but was wondering if 12 or 18vdc would be enough. Basically I want a button that I push on a "control panel" to travel the 100ft to a relay which then turns on a 115vac supply. Like I said I'm having issues understanding the way relays are rated. Assuming I go with 24vdc I would need a relay with a coil rated at 24vdc and a N.O. switch that can handle 115vac at 10-20A, correct? You could use any voltage you like depending upon what guage wire you use for the 100ft link. Generally any voltage from 12V - 24V would be quite suitable if you use twin conductor cable with conductors of 0.4mm (26AWG) diameter (or better) copper. Understood All leds are either red or green and based on what I read are 2vdc at .020mA. I do have 3-4 blue leds which I read at 4vdc and .040mA (if memory serves) Could you explain "in series" and "in Parallel." The way I understand it (and I could be wrong) Parallel would be having power go from one led to the other in a chain? Serial would be a home run track, back to power, for each led. In this case parallel is the way I did it. (with a resistor for each led) Oh dear me.... are you sure you should be getting into a project involving 115Vac? If you don't understand what series and parallel connections for low voltage components such as leds then you could get yourself killed when playing around with lethal voltages and currents. Have you tried doing some basic research into the meaning of these terms? - Google is your friend... Could you please explain series and parallel so I can verify what I have already researched and read on the subject instead of just saying that if I don't understand it I'm to stupid to deal with it? I would never connect leds of different colours in a series string because they all have different voltage requirements. I would only connect leds of the same colour in any individual series string. I didn't. I have three different colors but no colors are mixed with other colors. Both my red and green leds are all 2VDC and the 3 Blues are 4VDC. Technically I could connect the red and greens but I didn't. Every single LED in the system also has its own dedicated resistor. I'm not using one resistor for the entire string because (from what I researched) a led with slightly different requirements could burnout. This thing already has almost 100 resistors if that give you an idea of the LEDs required. I didn't mean to imply that the PCBs are totally done. They are merely to the point where I can no longer put off relay selection. That all said, I don't doubt I'm doing things wrong and backwards, it is my first PCB from scratch. (I've repaired them at work) How about these: http://cgi.ebay.com/Tyco-Relays-SPST...PCB_W0QQitemZ1 20060224418QQihZ002QQcategoryZ42897QQrdZ1QQssPageN ameZWD1VQQcmdZViewItem It depends on what type of load you are planning to control with the relay output. That particular relay is only rated to switch 10A @ 250Vac into a resistive load. Also, it can only switch a maximum load of 280W. You would not use it to control an inductive load such as a 115Vac electric motor or pump. 10A should be fine. Just using standard home outlet to supply this thing. I can make sure I use a 10 breaker or I can build a 10A (or slightly less) fuse into the system. See full data sheet here http://relays.tycoelectronics.com/datasheets/OJ-OJE.pdf What type of load are you intending to drive? Boy you'll love this, A short circuit! Basically a low gauge wire connected to positive and negative that will burn up when the relay is tripped. A light bulb with out the glass, basically. I should say that I have already built this and used it twice it works quite well. The current system uses 115Vac at 15A for the entire system. I'm just redesigning to get the controls and the majority of the rest of the system at lower voltage. I thought of using 24VDC for the whole thing but a trace on one of the boards could burn up instead of the filament. Thats the reason for the relays to isolate the short from the rest of the system. I suppose I could have one PSU (24VDC) for the system side and another for the "short" side. it would be slightly safer. :-) |
#6
Posted to alt.electronics
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Power Requirements
On Thu, 14 Dec 2006 22:45:44 GMT, "SBFan2000"
wrote: "Ross Herbert" wrote in message .. . On Thu, 14 Dec 2006 02:02:22 GMT, "SBFan2000" wrote: I did pick out final components except for the relays. I'm not entirely understanding how they are rated. I left room on the PCBs to accomidate most relays pins. I had a good idea of the voltage I wanted to use. I had selected 24vdc but was wondering if 12 or 18vdc would be enough. Basically I want a button that I push on a "control panel" to travel the 100ft to a relay which then turns on a 115vac supply. Like I said I'm having issues understanding the way relays are rated. Assuming I go with 24vdc I would need a relay with a coil rated at 24vdc and a N.O. switch that can handle 115vac at 10-20A, correct? On reading the explanation of the type of load you wish to drive (last paragraph below) it seems I may have interpreted that you wanted the relay contact to control the 115Vac output. When you said "I would need a relay with a coil rated at 24vdc and a N.O. switch that can handle 115vac at 10-20A, correct?" I thought you were referring to the N.O. contact on the relay as the "N.O. switch" which needed to be rated for 115Vac at 10 - 20A, but it appears that the N.O. switch you were referring to may be the switch used to cause the operation of the 24V relay at the remote end of the 100 ft cable. Is this correct? The switch used to control the relay coil only needs to be capable of handling a maximum of 1 - 2A at the operating voltage of 24Vdc. It won't matter if you do use a higher rated switch for this function. A sketch of what you are trying to achieve would be helpful. You could use any voltage you like depending upon what guage wire you use for the 100ft link. Generally any voltage from 12V - 24V would be quite suitable if you use twin conductor cable with conductors of 0.4mm (26AWG) diameter (or better) copper. Understood All leds are either red or green and based on what I read are 2vdc at .020mA. I do have 3-4 blue leds which I read at 4vdc and .040mA (if memory serves) Could you explain "in series" and "in Parallel." The way I understand it (and I could be wrong) Parallel would be having power go from one led to the other in a chain? Serial would be a home run track, back to power, for each led. In this case parallel is the way I did it. (with a resistor for each led) Oh dear me.... are you sure you should be getting into a project involving 115Vac? If you don't understand what series and parallel connections for low voltage components such as leds then you could get yourself killed when playing around with lethal voltages and currents. Have you tried doing some basic research into the meaning of these terms? - Google is your friend... Could you please explain series and parallel so I can verify what I have already researched and read on the subject instead of just saying that if I don't understand it I'm to stupid to deal with it? Basic explanation of series and parallel circuits http://www.allaboutcircuits.com/vol_1/chpt_5/1.html Connecting LED's in series (20mA types) http://unclean.org/howto/led_circuit.html If you haven't been here then it is a good place to start http://led.linear1.org/ They have a LED series parallel calculator wizard http://led.linear1.org/led.wiz I would never connect leds of different colours in a series string because they all have different voltage requirements. I would only connect leds of the same colour in any individual series string. I didn't. I have three different colors but no colors are mixed with other colors. Both my red and green leds are all 2VDC and the 3 Blues are 4VDC. Technically I could connect the red and greens but I didn't. Every single LED in the system also has its own dedicated resistor. I'm not using one resistor for the entire string because (from what I researched) a led with slightly different requirements could burnout. This thing already has almost 100 resistors if that give you an idea of the LEDs required. Try using the LED calculator wizard in the link above to check out the circuit arrangement for each of the LED colour arrays you are building. I didn't mean to imply that the PCBs are totally done. They are merely to the point where I can no longer put off relay selection. That all said, I don't doubt I'm doing things wrong and backwards, it is my first PCB from scratch. (I've repaired them at work) How about these: http://cgi.ebay.com/Tyco-Relays-SPST...PCB_W0QQitemZ1 20060224418QQihZ002QQcategoryZ42897QQrdZ1QQssPage NameZWD1VQQcmdZViewItem It depends on what type of load you are planning to control with the relay output. That particular relay is only rated to switch 10A @ 250Vac into a resistive load. Also, it can only switch a maximum load of 280W. You would not use it to control an inductive load such as a 115Vac electric motor or pump. 10A should be fine. Just using standard home outlet to supply this thing. I can make sure I use a 10 breaker or I can build a 10A (or slightly less) fuse into the system. See full data sheet here http://relays.tycoelectronics.com/datasheets/OJ-OJE.pdf What type of load are you intending to drive? Boy you'll love this, A short circuit! Basically a low gauge wire connected to positive and negative that will burn up when the relay is tripped. A light bulb with out the glass, basically. I should say that I have already built this and used it twice it works quite well. The current system uses 115Vac at 15A for the entire system. I'm just redesigning to get the controls and the majority of the rest of the system at lower voltage. I thought of using 24VDC for the whole thing but a trace on one of the boards could burn up instead of the filament. Thats the reason for the relays to isolate the short from the rest of the system. I suppose I could have one PSU (24VDC) for the system side and another for the "short" side. it would be slightly safer. :-) You will needa separate low power 24V dc supply to drive the relay coil - 100mA output capability would be suitable for the relay you have nominated. Use a separate high power 24V dc supply for the output (load side). This will need to be a fairly robust supply and may not need to be a regulated supply - a simple brute force mains transformer, bridge rectifier and filter capacitor arrangement with a hefty output circuit breaker or fuse (say 50A). The problem I see for the relay you have nominated is that the relay contacts will either be welded together or simply blasted away as soon as they make to supply 24V to the short circuit load. It is not going to be suitable for what you want to do. A pcb mounted relay will not be the way to go. For the function you require to perform you need a heavy duty contactor or mercury relay to handle the fast high current surge you will produce. Something like these would be suitable http://www.tempco.com/Accessories/Me...ent_Relays.htm Note: to drive the 24V dc coil of a RLY01355 (35A rating) you would need a 24Vdc coil supply capable of around 250mA. |
#7
Posted to alt.electronics
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Power Requirements
On 2006-12-14, Ross Herbert wrote:
I would never connect leds of different colours in a series string because they all have different voltage requirements. I would only connect leds of the same colour in any individual series string. theres no risa as long as the LEDs are all happy with the same current, LEDs aren't controlled by voltage anyway, they're controlled by current and drop whatever voltage they need. Bye. Jasen |
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