Ignition circuit help
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Chuck:
Yes. A set of points or a switch connected to ground from the point labeled "OUT" now from the hall sensor would work just fine. No condenser (capacitor) or other parts required.
Perhaps Steve can draw that option for us.
Sage
Yes. A set of points or a switch connected to ground from the point labeled "OUT" now from the hall sensor would work just fine. No condenser (capacitor) or other parts required.
Perhaps Steve can draw that option for us.
Sage
Chuck!
I did not consider the terminal blocks in that post. The only reason I put terminals on the board is so I will be able to change it out easily if it fails at one of the 2 shows I display at. If it's going to fail, that's where it will happen.
canadianhorsepower
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Hi I don't know if it's because it makes you feel better or if your just enjoying
contradicting what I'm saying, but the end result is unfair to post readers.
I think that your bright enought to know that 6 inch of twisted pairs of wire will make noise in a circuit, a mechanical switch is even worst. I think that you also know that debouncing circuit ( to eliminate noise from a switch)is very popular, that using a matching capacitor is a common practice, then why not playing it safe with your buddy and tell them the truth.
I know and You know that a small capacitor across the switch or the point
wont affect the circuit. But you also know that if one was needed and was not install then problem will happen.
Steve, a small cap .01uf is like 4 cents put one in it's like inssurance to a good working circuit
Mosey
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I for one, enjoy the polite and respectful tone of this forum. Please eliminate the harsh and possibly antagonistic aspects of your posts, so the wisdom and knowledge can stand on their own. Thanks,Hi I don't know if it's because it makes you feel better or if your just enjoying
contradicting what I'm saying, but the end result is unfair to post readers.
I think that your bright enought to know that 6 inch of twisted pairs of wire will make noise in a circuit, a mechanical switch is even worst. I think that you also know that debouncing circuit ( to eliminate noise from a switch)is very popular, that using a matching capacitor is a common practice, then why not playing it safe with your buddy and tell them the truth.
I know and You know that a small capacitor across the switch or the point
wont affect the circuit. But you also know that if one was needed and was not install then problem will happen.
Steve, a small cap .01uf is like 4 cents put one in it's like inssurance to a good working circuit
Mosey
canadianhorsepower
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Mosey, sorry to desapoint you I dont see any thing beeing impolite or disrespectful. I'm only describing what's going on and thats it.
I think that if someone is asking for help it is mostly because of a lack of knowledge and should not be side track for any reason.
cheers
Hi Steve,
I hope your experimentation is going well. I agree with Luc and Sage that spinning some magnets would be an ideal test whether you use a small electric motor or spin a disc with a variable speed drill or whatever might be handy for you. I would try to keep the magnet spacing diameter the same as it will be on your engine and use the same magnets you intend to use.
Sorry this post is so long winded but maybe it might be beneficial to some folks. If you choose to ignore this post I certainly understand.
I have built on your schematic a little and offer a couple of suggestions for experimentation. Your circuit is coming along nicely and I think it will work as is so take my ideas for just what they are. A possible way to improve your circuit.
Both Q1 and Q2 in your circuit will be used as switches. Therefore, there is no need to bias either transistor as you would if you were building an amplifier. That means that the only purpose for R1 and R4 are to keep the transistor base from floating when the transistor is off. If neither R1 or R4 were present then there is a chance the transistor could be turned on from transient current surges with enough amplitude to forward bias the transistor. Rule of thumb is R1 and R4 should be 10x R2 and R3 respectively which I have shown in the drawing. The actual value for R1 and R4 doesn't really matter so much as long as it keeps the base of the transistor pinned close to the supply rail when the transistor is off (12V for Q3 and ground for Q4). The problem with making R1 and R4 too small is that the resistors will rob part of the current that you want to drive the transistor base to drive your coil. For instance, as drawn originally, R4 is 1000 ohms. Q2 is a darlington transistor so the turn on voltage is going to be approximately 1.5V. At 1000 ohms the current through R4 will be 1.5 mA. Max current through R3 will be (12V - approx .7V for 2N3906 emmiter diode - 1.5V for BU941 darlington emitter pair) = 9.8V / 470 ohms = 20.8 mA. Subtract the 1.5 mA in parallel with Q2's base and you have about 19.4 mA. Multiply that by 300, which is approximately the gain of Q2 and you have a maximum of about 5.82A to drive your coil. Using a value of 4.7k for R4 would result in a current through R4 of approx 0.3 mA which would result in approx 20.5 mA hitting the base of Q2 or 6.15A through your coil. Not a huge difference (+5.4% increase) but illustrates the point.
I am also suggesting the use of D1 (1N914 or 1N4148) between the output of the SS441A and ground as shown. I couldn't find any data for the output transistor in the SS441A data sheet but your BU941 output transistor has an internal protection diode that will provide a current path when the ignition coil collapses and creates a spark. That current path will result in a short duration voltage surge (on the order of a few hundred volts) of opposite polarity that could quite possibly wipe out the SS441A output transistor. The diode will prevent that.
I am also suggesting the use of a filtering capacitor (C1) placed as close as possible to the power terminals of the SS441A. The SS441A has an internal voltage regulator and the capacitor will help remove any surges from the power supply. My preference would be a tantalum capacitor but an electrolytic (around 100uf) and a ceramic disk (around .1 uf) in parallel would probably work equally as well.
Luc and Sage both have correctly said that inverting the signal so the magnetic pulse discharges instead of charges the coil may work well for your motor considering you will be using a "wasted spark" setup for your motor. Your circuit lends itself well to inversion because your output transistor is a darlington and will require 1.5 volts or so to turn it on. The output transistor of your SS441A will saturate @ about .4 volts which will definitely turn the BU941 off. The benefit is that your coil will have more than enough time to charge up. The downside, as Luc and Sage have both pointed out is:
1) reduced battery life
2) your coil may run hot
3) your output transistor will definitely run hotter
Best regards,
Les
I hope your experimentation is going well. I agree with Luc and Sage that spinning some magnets would be an ideal test whether you use a small electric motor or spin a disc with a variable speed drill or whatever might be handy for you. I would try to keep the magnet spacing diameter the same as it will be on your engine and use the same magnets you intend to use.
Sorry this post is so long winded but maybe it might be beneficial to some folks. If you choose to ignore this post I certainly understand.
I have built on your schematic a little and offer a couple of suggestions for experimentation. Your circuit is coming along nicely and I think it will work as is so take my ideas for just what they are. A possible way to improve your circuit.
Both Q1 and Q2 in your circuit will be used as switches. Therefore, there is no need to bias either transistor as you would if you were building an amplifier. That means that the only purpose for R1 and R4 are to keep the transistor base from floating when the transistor is off. If neither R1 or R4 were present then there is a chance the transistor could be turned on from transient current surges with enough amplitude to forward bias the transistor. Rule of thumb is R1 and R4 should be 10x R2 and R3 respectively which I have shown in the drawing. The actual value for R1 and R4 doesn't really matter so much as long as it keeps the base of the transistor pinned close to the supply rail when the transistor is off (12V for Q3 and ground for Q4). The problem with making R1 and R4 too small is that the resistors will rob part of the current that you want to drive the transistor base to drive your coil. For instance, as drawn originally, R4 is 1000 ohms. Q2 is a darlington transistor so the turn on voltage is going to be approximately 1.5V. At 1000 ohms the current through R4 will be 1.5 mA. Max current through R3 will be (12V - approx .7V for 2N3906 emmiter diode - 1.5V for BU941 darlington emitter pair) = 9.8V / 470 ohms = 20.8 mA. Subtract the 1.5 mA in parallel with Q2's base and you have about 19.4 mA. Multiply that by 300, which is approximately the gain of Q2 and you have a maximum of about 5.82A to drive your coil. Using a value of 4.7k for R4 would result in a current through R4 of approx 0.3 mA which would result in approx 20.5 mA hitting the base of Q2 or 6.15A through your coil. Not a huge difference (+5.4% increase) but illustrates the point.
I am also suggesting the use of D1 (1N914 or 1N4148) between the output of the SS441A and ground as shown. I couldn't find any data for the output transistor in the SS441A data sheet but your BU941 output transistor has an internal protection diode that will provide a current path when the ignition coil collapses and creates a spark. That current path will result in a short duration voltage surge (on the order of a few hundred volts) of opposite polarity that could quite possibly wipe out the SS441A output transistor. The diode will prevent that.
I am also suggesting the use of a filtering capacitor (C1) placed as close as possible to the power terminals of the SS441A. The SS441A has an internal voltage regulator and the capacitor will help remove any surges from the power supply. My preference would be a tantalum capacitor but an electrolytic (around 100uf) and a ceramic disk (around .1 uf) in parallel would probably work equally as well.
Luc and Sage both have correctly said that inverting the signal so the magnetic pulse discharges instead of charges the coil may work well for your motor considering you will be using a "wasted spark" setup for your motor. Your circuit lends itself well to inversion because your output transistor is a darlington and will require 1.5 volts or so to turn it on. The output transistor of your SS441A will saturate @ about .4 volts which will definitely turn the BU941 off. The benefit is that your coil will have more than enough time to charge up. The downside, as Luc and Sage have both pointed out is:
1) reduced battery life
2) your coil may run hot
3) your output transistor will definitely run hotter
Best regards,
Les
Thanks Les, Dsage, CHP, but it looks as if i'm moving on to plan B. The coil would not fire. I could see the voltage changing at the primary side but no spark. I am going to figure out another way. Even if the circuit didn't work for me, at least there is a good circuit that came out of it. I am sure it will help someone here. I'm sorry all your hard work added up to nothing but i'm sure if it were a standard coil the circuit would have worked just fine.
canadianhorsepower
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Hey Steve,
I'll buy them I have a serious problem when a piece of wire
put together by a human beeing won't respond:wall: if (when) I'll suceed
if you wont them back no problemo you'll get them back like you mentioned before they belong
to that comp/engine project
What's your plan B???
I don't know how much electronic you do, but if you send me a pm I will email you this book
good luck, the "Paint artist"Rof}Rof}Rof}
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Steve, have you tried the coil with a standard auto condenser and points or some other kind of make / break? I know a regular auto ignition system with points and a coil won't work without the condenser.
Chuck
Chuck
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Here are some schematics to Ignition Circuits that might be useful...
http://www.5bears.com/tim4.htm
Chuck
http://www.5bears.com/tim4.htm
Chuck
canadianhorsepower
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I think that with all what Steve heard about with ignition :rant::wall:???:shrug:stickpokescratch.gif:-[th_rulze*club*:redface2:*discussion*
The next project will be a DIESEL engine Rof}Rof}Rof}Rof}Rof}
The next project will be a DIESEL engine Rof}Rof}Rof}Rof}Rof}
Hello Chuck!
It will fire a standard coil. It's the duel coil that doesn't want to work.
I don't have one yet. Need to take a step back and figure out what I want to do.
Lakc
Well-Known Member
I have been working on plan B all along.
Taking a break now, as I am tired of debugging a/d and interrupt code. Good news is I managed to create very scary voltages across large capacitors. Bad news is I smoked the two Pic16F690's I was using for development. :rant:But the spark that did it was glorious
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Les:
All good suggestions. I'm not sure where the original circuits were coming from. My efforts were simply to eliminate some of the more obvious issues with the circuit(s) as presented.
I agree that all of your suggestings would improve / protect the circuit beyond the original basic design presented. Having said that, the circuit should (and apparently does) work as it has evolved. Adding any of your suggestions would certainly make it more robust.
If I had the luxury of starting over I'd design the IGBT circuit I presented way back in post 17. I guess it's probably not perfect either but we are always trying to balance complexity with benefits / cost.
Re: the other circuit:
Although having the coil energized all of the time would give you a spark right away (when the transistor is triggered off) it might lead to more problems than benefits. The transistor would be dissipating 6A x 1.5 volts = 9 watts almost contunuously. Also, most guys are using batteries of about 7Ah (at a 20hour rate). With 6A continuous the battery might not last long. Of course this is how car ignitions operate but then there is an alternator as backup.
I'm sure Steve is frustrated at the moment. He says it fires a standard coil so I'll have to assume the dual output coil has problems. I'll think about it a bit and suggest a test.
Canadianhorsepower:
The input impedane of the circuit with the switch actvating the transistor directly is more or less about 680 ohms. It is unlikely there would be any "noise" on the switch leads large enough to bias the transistor on (requiring at least 10ma of current). But, like you said, small capacitors are cheap and a small .01uf wouldn't hurt.
(Now don't anyone criticize that statement because at some point the capacitor will slow down the transistor switching off time, but we won't go there).
There are lots of things that "could" be added to any circuit and most times you need to test these things on the bench, see where you have problems, and fix those problems.
Unfortunate that you chose to accuse me of lying to everyone that the capacitor IS need and I was somehow CHOOSING to not tell them about it.
Sage
All good suggestions. I'm not sure where the original circuits were coming from. My efforts were simply to eliminate some of the more obvious issues with the circuit(s) as presented.
I agree that all of your suggestings would improve / protect the circuit beyond the original basic design presented. Having said that, the circuit should (and apparently does) work as it has evolved. Adding any of your suggestions would certainly make it more robust.
If I had the luxury of starting over I'd design the IGBT circuit I presented way back in post 17. I guess it's probably not perfect either but we are always trying to balance complexity with benefits / cost.
Re: the other circuit:
Although having the coil energized all of the time would give you a spark right away (when the transistor is triggered off) it might lead to more problems than benefits. The transistor would be dissipating 6A x 1.5 volts = 9 watts almost contunuously. Also, most guys are using batteries of about 7Ah (at a 20hour rate). With 6A continuous the battery might not last long. Of course this is how car ignitions operate but then there is an alternator as backup.
I'm sure Steve is frustrated at the moment. He says it fires a standard coil so I'll have to assume the dual output coil has problems. I'll think about it a bit and suggest a test.
Canadianhorsepower:
The input impedane of the circuit with the switch actvating the transistor directly is more or less about 680 ohms. It is unlikely there would be any "noise" on the switch leads large enough to bias the transistor on (requiring at least 10ma of current). But, like you said, small capacitors are cheap and a small .01uf wouldn't hurt.
(Now don't anyone criticize that statement because at some point the capacitor will slow down the transistor switching off time, but we won't go there).
There are lots of things that "could" be added to any circuit and most times you need to test these things on the bench, see where you have problems, and fix those problems.
Unfortunate that you chose to accuse me of lying to everyone that the capacitor IS need and I was somehow CHOOSING to not tell them about it.
Sage
canadianhorsepower
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:bow::bow::bow:Rof}Rof}Rof}:bow::bow::bow:
does that make youre ego better
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Steve:
Sorry to bug you.
I'd just like to close the loop on a few things suggested earlier.
Did you (or could you) try the dual output coil by:
Use a spark plug in free air (not in the engine)
Connect a clip lead from one HV lead to the tower of the plug
Take a second clip lead from the other HV lead to the threads of the plug. Use no grounds on the plug.
I'm sure you probably tried this but I didn't see the results of this test.
I think you responded that the circuit will fire your old school coil - right? If not I /we can suggest a few circuit troubleshooting ideas.
One right off the top:
Arrange a voltmeter across the primary of the dual output coil (+/- leads), preferrably with clip leads so your hands are free.
With the magnet NOT activating the hall sensor you should measure zero volts.
Activate the hall sensor with a magnet JUST LONG ENOUGH to take a stable measurement on the meter.
What do you see?
I think you said the resistance of the coil primary was 0.8 ohms?
Did you take into consideration the resistance of your meter leads? Short your leads together and take that measurement and subtract it from your coil measurement. Why? because the meter leads might measure as much as 0.2 ohms themselves.
What do you get?
It's difficult to tell what "normal" would be for any coil. You might compare it to your "good" coil. I have an old-school coil here and it measures 0.2 ohms. (Not sure where I'm going with this one).
Sage
Sorry to bug you.
I'd just like to close the loop on a few things suggested earlier.
Did you (or could you) try the dual output coil by:
Use a spark plug in free air (not in the engine)
Connect a clip lead from one HV lead to the tower of the plug
Take a second clip lead from the other HV lead to the threads of the plug. Use no grounds on the plug.
I'm sure you probably tried this but I didn't see the results of this test.
I think you responded that the circuit will fire your old school coil - right? If not I /we can suggest a few circuit troubleshooting ideas.
One right off the top:
Arrange a voltmeter across the primary of the dual output coil (+/- leads), preferrably with clip leads so your hands are free.
With the magnet NOT activating the hall sensor you should measure zero volts.
Activate the hall sensor with a magnet JUST LONG ENOUGH to take a stable measurement on the meter.
What do you see?
I think you said the resistance of the coil primary was 0.8 ohms?
Did you take into consideration the resistance of your meter leads? Short your leads together and take that measurement and subtract it from your coil measurement. Why? because the meter leads might measure as much as 0.2 ohms themselves.
What do you get?
It's difficult to tell what "normal" would be for any coil. You might compare it to your "good" coil. I have an old-school coil here and it measures 0.2 ohms. (Not sure where I'm going with this one).
Sage
I have been working on plan B all along.
But the spark that did it was glorious
Did you want me to bring this coil to you? I can drop it off anytime this week. I have a brand new one still in the box.
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