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#1
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de-bounce
I am tinkering with some 25 year old TTL logic chips and I need to make a
de-bounce circuit that will stay on for the duration of a the push-button. I have several ways already to debounce the button close, but they are one-shot pulses that have thein own duration. I need both the close and open of the push button to be debounced and it to keep the duration of the button push. I have seen schmitt trigger circuits (that I have tried to build but dont seem to work (have to triple check the wiring)), and other RC variations. What kind of easily accessible parts (like from Radio Shack) should I be looking for. It all has to run on 4-AA batteries. Looked an some op-amp parts at RS but they seem to all require 18v, or more, supply. BTW, the debouncing solution needs to be acurate to within about 1 milli-second. Henry |
#2
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de-bounce
"Henry" wrote in message
om... I am tinkering with some 25 year old TTL logic chips and I need to make a de-bounce circuit that will stay on for the duration of a the push-button. I have several ways already to debounce the button close, but they are one-shot pulses that have thein own duration. I need both the close and open of the push button to be debounced and it to keep the duration of the button push. I have seen schmitt trigger circuits (that I have tried to build but dont seem to work (have to triple check the wiring)), and other RC variations. What kind of easily accessible parts (like from Radio Shack) should I be looking for. It all has to run on 4-AA batteries. Looked an some op-amp parts at RS but they seem to all require 18v, or more, supply. BTW, the debouncing solution needs to be acurate to within about 1 milli-second. Henry The easiest way is to use a pushbutton with Form C contact (single pole, double throw) connected to 2 cross connected NOR gates so that when the moving contact hits one pole connected to one NOR gate the cross connection latches in one state and when the moving contact hits the other pose connected to the other NOR gate the cross connection latches in the other state. Thus you get a latch circuit the follows the pushbutton with no glitches. If you don't know how to implement this let me I can give you more details Dan -- Dan Hollands 1120 S Creek Dr Webster NY 14580 585-872-2606 www.QuickScoreRace.com |
#3
Posted to alt.electronics
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de-bounce
"Dan Hollands" wrote in message ... "Henry" wrote in message om... I am tinkering with some 25 year old TTL logic chips and I need to make a de-bounce circuit that will stay on for the duration of a the push-button. I have several ways already to debounce the button close, but they are one-shot pulses that have thein own duration. I need both the close and open of the push button to be debounced and it to keep the duration of the button push. I have seen schmitt trigger circuits (that I have tried to build but dont seem to work (have to triple check the wiring)), and other RC variations. What kind of easily accessible parts (like from Radio Shack) should I be looking for. It all has to run on 4-AA batteries. Looked an some op-amp parts at RS but they seem to all require 18v, or more, supply. BTW, the debouncing solution needs to be acurate to within about 1 milli-second. Henry The easiest way is to use a pushbutton with Form C contact (single pole, double throw) connected to 2 cross connected NOR gates so that when the moving contact hits one pole connected to one NOR gate the cross connection latches in one state and when the moving contact hits the other pose connected to the other NOR gate the cross connection latches in the other state. Thus you get a latch circuit the follows the pushbutton with no glitches. If you don't know how to implement this let me I can give you more details Dan Thanks, but I have no control over the push button. Its a camera shutter. Might be mechanical, might be electronic. Either way it acts like a simple push button closing a circuit. The mechanical ones, of course have noise. I have an old camera that I want to try some specialy effects photography with. I also have a view camera that has a focal plane leaf shutter (built into the lens) that, in theory, should sync with a flash through its range of shutter speeds (up to 1/250 of a second.) Anyway, thanks. I will keep looking. Henry |
#4
Posted to alt.electronics
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de-bounce
Henry
Without some knowledge of the type and electrical charactoristis of the button it is hard to design a debounce circuit. Even with a mechanical switch are sure that need one - what is the button going to do -- Dan Hollands 1120 S Creek Dr Webster NY 14580 585-872-2606 www.QuickScoreRace.com "Henry" wrote in message ... "Dan Hollands" wrote in message ... "Henry" wrote in message om... I am tinkering with some 25 year old TTL logic chips and I need to make a de-bounce circuit that will stay on for the duration of a the push-button. I have several ways already to debounce the button close, but they are one-shot pulses that have thein own duration. I need both the close and open of the push button to be debounced and it to keep the duration of the button push. I have seen schmitt trigger circuits (that I have tried to build but dont seem to work (have to triple check the wiring)), and other RC variations. What kind of easily accessible parts (like from Radio Shack) should I be looking for. It all has to run on 4-AA batteries. Looked an some op-amp parts at RS but they seem to all require 18v, or more, supply. BTW, the debouncing solution needs to be acurate to within about 1 milli-second. Henry The easiest way is to use a pushbutton with Form C contact (single pole, double throw) connected to 2 cross connected NOR gates so that when the moving contact hits one pole connected to one NOR gate the cross connection latches in one state and when the moving contact hits the other pose connected to the other NOR gate the cross connection latches in the other state. Thus you get a latch circuit the follows the pushbutton with no glitches. If you don't know how to implement this let me I can give you more details Dan Thanks, but I have no control over the push button. Its a camera shutter. Might be mechanical, might be electronic. Either way it acts like a simple push button closing a circuit. The mechanical ones, of course have noise. I have an old camera that I want to try some specialy effects photography with. I also have a view camera that has a focal plane leaf shutter (built into the lens) that, in theory, should sync with a flash through its range of shutter speeds (up to 1/250 of a second.) Anyway, thanks. I will keep looking. Henry |
#5
Posted to alt.electronics
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de-bounce
Maybe this will work ?...
Solving Switch Bounce Problems http://www.embedded.com/showArticle....cleID=18902552 TTL. So use a TTL, 74, LS, ALS, hex inverter for a debouncer? Your using TTL now so there shouldn't be a problem with 1 milli-second. If not fast enough, look at the ALS, S, AS TTL logic families ? "Henry" wrote in message om... I am tinkering with some 25 year old TTL logic chips and I need to make a de-bounce circuit that will stay on for the duration of a the push-button. I have several ways already to debounce the button close, but they are one-shot pulses that have thein own duration. I need both the close and open of the push button to be debounced and it to keep the duration of the button push. I have seen schmitt trigger circuits (that I have tried to build but dont seem to work (have to triple check the wiring)), and other RC variations. What kind of easily accessible parts (like from Radio Shack) should I be looking for. It all has to run on 4-AA batteries. Looked an some op-amp parts at RS but they seem to all require 18v, or more, supply. BTW, the debouncing solution needs to be acurate to within about 1 milli-second. Henry |
#6
Posted to alt.electronics
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de-bounce
Yes, I have read how difficult of a problem that it is. And what makes it
worse is that I wanted to make it a general circuit good for mony, if not most, camera shutters whether they be mechanical or digital. One of the things is that I wanted to make a timer to measure how long a shutter is open (old mechanical camera shutters can vary (as much as 20%) from the indicated shutter speed. I have an idea for a solution, but is seems odd. Henry "Dan Hollands" wrote in message ... Henry Without some knowledge of the type and electrical charactoristis of the button it is hard to design a debounce circuit. Even with a mechanical switch are sure that need one - what is the button going to do -- Dan Hollands 1120 S Creek Dr Webster NY 14580 585-872-2606 www.QuickScoreRace.com "Henry" wrote in message ... "Dan Hollands" wrote in message ... "Henry" wrote in message om... I am tinkering with some 25 year old TTL logic chips and I need to make a de-bounce circuit that will stay on for the duration of a the push-button. I have several ways already to debounce the button close, but they are one-shot pulses that have thein own duration. I need both the close and open of the push button to be debounced and it to keep the duration of the button push. I have seen schmitt trigger circuits (that I have tried to build but dont seem to work (have to triple check the wiring)), and other RC variations. What kind of easily accessible parts (like from Radio Shack) should I be looking for. It all has to run on 4-AA batteries. Looked an some op-amp parts at RS but they seem to all require 18v, or more, supply. BTW, the debouncing solution needs to be acurate to within about 1 milli-second. Henry The easiest way is to use a pushbutton with Form C contact (single pole, double throw) connected to 2 cross connected NOR gates so that when the moving contact hits one pole connected to one NOR gate the cross connection latches in one state and when the moving contact hits the other pose connected to the other NOR gate the cross connection latches in the other state. Thus you get a latch circuit the follows the pushbutton with no glitches. If you don't know how to implement this let me I can give you more details Dan Thanks, but I have no control over the push button. Its a camera shutter. Might be mechanical, might be electronic. Either way it acts like a simple push button closing a circuit. The mechanical ones, of course have noise. I have an old camera that I want to try some specialy effects photography with. I also have a view camera that has a focal plane leaf shutter (built into the lens) that, in theory, should sync with a flash through its range of shutter speeds (up to 1/250 of a second.) Anyway, thanks. I will keep looking. Henry |
#7
Posted to alt.electronics
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de-bounce
Thanks for the link and I have already been to that site. Great site and I
am using it as one of my references. Problem is that I dont have any 74 series with schmitt triggers. I looked thourgh my box of old TTL chips. I have nand gates, counters, flipflops, 555 timers, (plus transistors, resistors, capacitors, etc) but nothing with a schmitt trigger built in. Being out in a rural area and financially drained (from caregiving for my mother in her last years) I can not justify $25 minimum ordering with S&H for a $0.49 chip. Radio Shack does not carry these, and my attempts to build my own from transistors in my box-o-ole-lectronics seems to have failed. Lacking a scope I cant really tell if what I assemble is working. So I am continuing by trial and error. All I know is that with what I have built so far I am getting multiple triggers from the old camera shutter that I have. That is my noisy switch that I am using. Henry "newtype" wrote in message 5.254... Maybe this will work ?... Solving Switch Bounce Problems http://www.embedded.com/showArticle....cleID=18902552 TTL. So use a TTL, 74, LS, ALS, hex inverter for a debouncer? Your using TTL now so there shouldn't be a problem with 1 milli-second. If not fast enough, look at the ALS, S, AS TTL logic families ? "Henry" wrote in message om... I am tinkering with some 25 year old TTL logic chips and I need to make a de-bounce circuit that will stay on for the duration of a the push-button. I have several ways already to debounce the button close, but they are one-shot pulses that have thein own duration. I need both the close and open of the push button to be debounced and it to keep the duration of the button push. I have seen schmitt trigger circuits (that I have tried to build but dont seem to work (have to triple check the wiring)), and other RC variations. What kind of easily accessible parts (like from Radio Shack) should I be looking for. It all has to run on 4-AA batteries. Looked an some op-amp parts at RS but they seem to all require 18v, or more, supply. BTW, the debouncing solution needs to be acurate to within about 1 milli-second. Henry |
#8
Posted to alt.electronics
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de-bounce
On 2005-12-25, Henry wrote:
I am tinkering with some 25 year old TTL logic chips and I need to make a de-bounce circuit that will stay on for the duration of a the push-button. I have several ways already to debounce the button close, but they are one-shot pulses that have thein own duration. I need both the close and open of the push button to be debounced and it to keep the duration of the button push. I have seen schmitt trigger circuits (that I have tried to build but dont seem to work (have to triple check the wiring)), and other RC variations. What kind of easily accessible parts (like from Radio Shack) should I be looking for. It all has to run on 4-AA batteries. Looked an some op-amp parts at RS but they seem to all require 18v, or more, supply. BTW, the debouncing solution needs to be acurate to within about 1 milli-second. something like this might do the trick +------------------+--+5 | | [10K] [10K] | | \ +-----+ +---+---- out in /\ | | | | -------[1K]---+---[100K]---(---+ | | / | / | | | r2 | |/ | \ | +-[100K]-)-| __L__ \| | | |\| ~~T~~ |-+---[330k]-+ -\ | 0.1uF |/| R1 | | /- | | | | -------------+------------+------------------+------- the input may need a pull up, the output should be capable of driving TTL. small capacitors in parallel with the base resistors may help with the waveform a bit. increasing the timing capacitor to 1uF may help if you're still seeing bounce with this, Bye. Jasen |
#9
Posted to alt.electronics
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de-bounce
On Mon, 26 Dec 2005 01:17:50 -0500, "Henry"
wrote: Thanks for the link and I have already been to that site. Great site and I am using it as one of my references. Problem is that I dont have any 74 series with schmitt triggers. I looked thourgh my box of old TTL chips. I have nand gates, counters, flipflops, 555 timers, (plus transistors, resistors, capacitors, etc) but nothing with a schmitt trigger built in. Being out in a rural area and financially drained (from caregiving for my mother in her last years) I can not justify $25 minimum ordering with S&H for a $0.49 chip. Radio Shack does not carry these, and my attempts to build my own from transistors in my box-o-ole-lectronics seems to have failed. Lacking a scope I cant really tell if what I assemble is working. So I am continuing by trial and error. All I know is that with what I have built so far I am getting multiple triggers from the old camera shutter that I have. That is my noisy switch that I am using. --- Henry, please bottom post, since it makes it much easier to follow the chronological flow of the thread. Thanks. As for your problem, the only really sensible solution is the one Dan Hollands offered, using a SPDT momentary switch and cross-coupled gates to form an RS latch. That way _totally_ eliminates all bounce and the period of the output signal is _precisely_ equal to the time it takes for the swich's common terminal to get from one contact to the other. If you've got a quad NAND (7400, LS00, HC00, etc.) and a SPST switch you can make a latch, like this: Vcc Vcc | | [1K] [1K] | | O--| --O---A |NC | NO NAND Y--+--- OUT | O +--B | | | | | | GND | A--+ | +--Y NAND | B--+ | | +------------------+ Now, when you press the switch, the instant the common hits the normally open contact, OUT will go high and stay high for as long as you keep the switch pressed. When you release the switch, OUT will go low the instant the arm hits the NC contact and it will stay that way until you again press the switch. Re. your other post, about measuring the actual shutter timing, what's your idea and what kind of test equipment have you got? -- John Fields Professional Circuit Designer |
#10
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de-bounce
Henry, please bottom post, since it makes it much easier to follow
the chronological flow of the thread. Thanks. Thanks, I will try to keep that is mind. Im on several different forums (photography, sci-fi, etc.) and different ones have different preferences, if any. Ussually I follow with what the last person used, or I try to. Thanks everyone for all the help and suggestions. I will be giving several suggested circuits a try soon. Assuming that I can build them correctly, and have the parts. Henry |
#11
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de-bounce
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