Ignition driver problem

[NanoSoft]

Ok so my ignition setup right now is a piece of junk and never works so i decided to build a electric circuit based on a 555 timer chip. I found many plans on the Internet and built many of them on a breadboard. The problem is i can't get a spark bigger then around .1 mm

The circuits work but i can't get a very big spark. This goes for all three different designs i tried. I tried a different battery and that didn't help so i tried a different coil and that didn't work either. Does anyone have any ideas?

I think that maybe all my coils might be weak and not designed to produce as high of a voltage as i would like. Could that be the problem or could it be that i am using a breadboard and haven't soldered the components. Any help is welcome.

Nanosoft

[resosys]

Ok so my ignition setup right now is a piece of junk and never works so i decided to build a electric circuit based on a 555 timer chip. I found many plans on the Internet and built many of them on a breadboard. The problem is i can't get a spark bigger then around .1 mm

The circuits work but i can't get a very big spark. This goes for all three different designs i tried. I tried a different battery and that didn't help so i tried a different coil and that didn't work either. Does anyone have any ideas?

Some of the designs out there are horrible. I have found that coils can make a big difference, but you should be able to get a much stronger spark than .1mm.

I think that maybe all my coils might be weak and not designed to produce as high of a voltage as i would like. Could that be the problem or could it be that i am using a breadboard and haven't soldered the components. Any help is welcome.

There is a design posted on this forum somewhere that works well. I've also got one that works well but I don't have the schematic drawn up and I need to do a bit of filtering to keep the HV off the battery leads.

If the designs you're using have a diode across the coil terminals, the spark will be considerably smaller since the diode kills the coil's need to ring when the field collapses.

A design with a big darlington or fet seems to be the way to go.

Post links to the designs you're using and I can take a look at them.

I'd recommend building the circuit that was posted to the forum some months back. It's better than mine.

Chris

[resosys]

Here's the thread for the recent spark circuit:

http://www.pulse-jets.com/phpbb2/viewto ... rk+circuit

[maina]

helo.. if you want a big spark plug..
see this post there are two inition coil... bye bye

http://www.pulse-jets.com/phpbb2/viewtopic.php?t=1751

[Ray]

One of the most common mistakes made with a 555 timer ciruit type sparker is that people try to switch the power on and off, instead of switching the ground on and off. You want the coil to saturate, then discharge...switching the power usually doesn't allow the coil to saturate and most of the energy you want for a spark just goes to the ground of the battery, the easiest path. If you switch the ground (you'll have another ground path through the spark gap) it forces the energy through the area you want it when you open the ground to the coil.

You want the circuit to conduct through the coil most of the time, then when you pull the gound and you get a good spark out of it.

Make sure the duty cycle is around 50%

Make sure that the transistor you have is opening the ground, not the power. It should be between the negative post of the coil and ground.

The frequency should be fairly low...try for around 200 hz.

A diode across the transistor will help the transistor last longer...you want the anode to ground...it helps tame the inductive kick and protect the transistor.

Post the circuit you built, we can help you troubleshoot.

[NanoSoft]

Thank for your comments. Here are the circuits that I built.

Nanosoft

[Viv]

Attached is a coil drive circuit I have used with success, this is based on a transitorised capacitor discharge car ignition circuit, you can buy the whole thing as a kit from Velleman kits complete with heat sink, PCB, and all parts.

This used to be used on the BCVP project and puts out a scary hot spark.

To drive the unit use a duel 555 with one timer set to produce around 200 Hz, the second timer is set to about 50 Hz, the low speed timer is connected to the gate of the second so you get a series of 200 Hz high frequency pulses delivered at 50 Hz, these are fed to the pulse input of the coil driver circuit.

The idea is to get a short pulse of high frequency sparks 50 times a second instead of single sparks that most other ignition circuits produce.

It works and has been used by Nick and I for many years

Viv

[larry cottrill]

Viv -

Unfortunately, you haven't drawn the little arrow inside the transistors to show which is the emitter and which is the collector ;-)

L Cottrill

[Viv]

Viv -

Unfortunately, you haven't drawn the little arrow inside the transistors to show which is the emitter and which is the collector ;-)

L Cottrill

Bugger!

Viv

[Viv]

Viv -

Unfortunately, you haven't drawn the little arrow inside the transistors to show which is the emitter and which is the collector ;-)

L Cottrill

Just to please you Larry I added the arrow:-)

Viv

[Viv]

*cough*there'stwotransistors*cough*

Why have two and three resistors in paralell? Was that just what you had on hand, or is there a reason to not replace R1 and R2 with one 165 ohm and R5 R6 and R7 with one 50 ohm?

Oh pick pick pick! ok theres two bleeding transistors but i is not a draftman! I will aks luk to do you a proper drawing OK! I did this in a paint program three years ago for my own use and I knew wich way they whent in.

Yes you can choose and use what ever resistors you have to hand as long as they add up to the required value and dissipation, the ones shown are easy to get off the shelf at low cost thats all.

Splitting R5 R6 R7 gives a smaller footprint as higher wattage resistors are bigger, and dont use wire wound types:-)

Viv

[Ray]

You built all three of these circuits?

The last one has the autocoil connected backwards...It should have the negative side to ground.

I didn't do the math to figure out the duty cycle and frequency for the 555, I'll just assume that its correct.

The second one has 3 2N3055's, you really only need one. Drop the 5K potentiometer from the circuit, the one between the 555 and the transistors. You don't need it and it will pby only prevent the transistors from turning on fully.

The first one shows a flyback transformer, I assume that you are using the car coil on all of them...

I would check several things...first make sure the circuit is built to the drawing. Check it, then check it again.

The one thing that none of the circuits you posted show is where to ground the high voltage out of the coil. You should not ground it at the negative terminal of the coil, you should ground it at the circuit ground. If you ground it at the neg. terminal of the coil, you won't have a ground when the transistor opens and thats when you get the spark...you should run your wire from the HV terminal to the spark gap, then from the spark gap to the battery.

Check that the 555 is oscillating...you could disconnect the coil and hook up a small speaker to the circuit momentarily...you should hear a tone...hook it up to the 555 after the 100 ohm resistor and before the transistor, you'll hear a quieter tone. After the transisters will pby be loud and may blow the speaker, so only hook it up for an instant. You need to check it on the output of the 555 and the output of the transistor to verify that the transistor is working OK. If it works before, but not after the transistor is blown.

Your autocoil might not be good. Check the resistance from the + to the - and from the HV terminal to the -. I don't know what coil you are using, but the manufacturer should be able to provide you with some specifications. You could always just put in a different coil that you know is good, and see if you get a better spark.

Do you have a heat sink on your transistor(s)? You'll need something. Even if its just a chunk of aluminum plate...

Lastly, you don't say what type of battery you are using. It needs to be capable of delivering quite a bit of current. A lead acid cell is best, the type you would use for a car or a motorcycle. Don't try to run it off of a battery charger, they usually don't filter the output, so it pulses...

Check these things then let me know if you are still having trouble.

[NanoSoft]

Thank you for the comments. Yes i built all three and all three work when hooked up to a speaker so i assume the circuits are working. I have switched between two batteries. Both were chareged and one was new so thats not it. So i think it is my coil but i switched coils and the same happend so maybe i need a better coil? Maybe a higher performance one for racing. Hop i figure it out soon. I will try your circuit Viv and see what happens. My bet is it will do the same as the others.

Nanosoft

[resosys]

Nanosoft,

What type of batteries are you using? You'll need to be able to deliver about 5 amps at 12V, or 3 amps minimum.

Also, my experience with the 3055 based circuits has been horrible. I'm a newbie with electronics, but have a couple of phd EE's at my disposal and they both have helped me work out the bugs in various circuits. The 3055 doesn't have enough gain and lets a lot of the HV ring during the colapse of the primary coil, back into the 555. I've gone through a lot of 555's and burned a lot of fingers in the 3055s.

I have used about 10 different coils, all of which are the standard variety. They all work. Some are stronger than others, but they all make nice hot sparks. I don't think you need a racing coil.

Are you coming to the meet? I'll hopefully have a few spark circuits built up on some pcb's I made. If so, you can have one or we can mess with yours to see if we can find the problems.

I'm hoping to design a new circuit in the coming months and I'll post a website howto when it's done.

Chris

[Ray]

what frequency are you running it at? have you tried a lower/higher one? Was the tone on the speaker very high pitched, or low pitched.

I would still check the ground for the spark gap. It can not be connected prior to the transistor, you must have a ground that returns directly to the battery.

If the gain of the transistor is a problem (and it could well be) you can connect the 2N3055's in a darlington pair configuration. Like the picture...