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Author Topic: Ignition Coil Won't Spark from Mosfet but DOES spark By Hand??? HELP!?  (Read 26533 times)

pha3z

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I'm trying to get an ignition coil to create sparks running it with a Mosfet powered by a 555 timer.   The Mosfet is definitely switching.  I checked it with resistor, ampmeter, and o-scope.  Everything is behaving predictably but when I use it to power a car Ignition Coil, I don't get any sparks.  I can tap the terminals of the Ignition coil by hand -- Even with it connected up to the mosfet circuit -- and get sparks.  But when I try to let the mosfet drive it, there are no sparks.  There is definitely current flowing.  And if I change the frequency to super low (like a pulse every second), the ampmeter is registering the pulses.  If I change the frequency to super high (like 100khz), I get averaged current flow on the ampmeter.  But I don't get sparks!!!!!  I also switched out mosfet with other kinds (different ratings).  Didn't fix it.

Anyone else ever run into this problem???

Here's a schematic similar to my setup:
http://www3.telus.net/chemelec/Projects/Car-Coil/Car-Coil-1.png

Hope someone else has had this problem before and can help!!

Thanks,
Jim

Rafael Ti

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Re: Ignition Coil Won't Spark from Mosfet but DOES spark By Hand??? HELP!?
« Reply #1 on: February 16, 2012, 02:50:30 PM »
I would advise you to use a driver between pin 3 of 555 and the gate of MOSfet. It looks like the output resistance of 555 is to big to drive the MOSfet correctly due to capacity G - S, and this is why u can't get sharp enough pulses. Check the TC4422 for instance... You can also try to increase the capacity of 1uF tantalum capacitor shown on diagram to say 100uF,or more, but it rather won't work.
The other reason could be that the Rds on of the transistor is to high comparing to impedance of coil and the curent you have is not enough to spark...

TinselKoala

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Re: Ignition Coil Won't Spark from Mosfet but DOES spark By Hand??? HELP!?
« Reply #2 on: February 17, 2012, 06:29:51 AM »
A mosfet driver will help, but I think the turn on- turn off time of the 640 is too slow anyway. Try a 510, and try the same circuit with a 2n3055 on a heatsink.
I used a 2n2222a to drive the gate of the mosfet in the flyback version of this circuit. Be careful !! The ignition coil can startle you but the flyback version can kill.

http://www.youtube.com/watch?v=VNL8QTS0sM0




TinselKoala

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Re: Ignition Coil Won't Spark from Mosfet but DOES spark By Hand??? HELP!?
« Reply #3 on: February 18, 2012, 10:02:19 PM »
Ignition coils don't work like that they are too of the flyback type just as regular CRT flyback transformer meaning they spark on field collapse.
So you slowly charge up the coil/magnetic field and when you switch it off the field suddenly collapses and this generates the high voltage for the spark.
In older setups a capacitor was charged and then discharged into the 0 ohm primary from the ignition coil which are configured as auto transformers and this worked very well.
It's called CDI for capacitor discharge ignition so you might want to take a look at that type of circuitry.

Ignition coils don't work like that?
Well, then..... I must have made some mistake.... because in my video above I show an ignition coil WORKING LIKE THAT. Don't I? And I even give the schematic so anyone with an ignition coil and a Radio Shack can build one and see whether or not ignition coils work like that.

The main differences between the ignition coil version and the flyback version is that the ignition coil has a heavy iron core and generally is driven at a frequency far from its resonant frequency, so all you get is voltage amplification by turns ratio. The flyback version uses a user-installed 10-turn primary, has no heavy iron core, and if done properly works at or close to its resonant frequency. So you get voltage amplification by standing wave resonance, like in a Tesla coil, and can make more dramatic sparks... until you fry the flyback transformer.

A capacitive discharge ignition system doesn't even HAVE an ignition coil. That's the whole point.
http://en.wikipedia.org/wiki/Capacitor_discharge_ignition

TinselKoala

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Re: Ignition Coil Won't Spark from Mosfet but DOES spark By Hand??? HELP!?
« Reply #4 on: February 19, 2012, 05:27:45 AM »
The transformers used in CDI systems are very different from ignition coils.

The OP of this thread asked for help with an ignition coil spark system using a 555 timer.  Are you being helpful?

Let's see your video demonstration of your circuit.

Magluvin

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Re: Ignition Coil Won't Spark from Mosfet but DOES spark By Hand??? HELP!?
« Reply #5 on: February 19, 2012, 06:05:14 AM »
here is a vid I have made using capacitive discharge of near 500v from a .13uf cap.

The small neon board from a scanner light, is charging the cap via an Avramenko plug via 1 leg of the neon transformer. By taking the other leg of the neon transformer and attaching it to an insulated wire wound around the ign coil can, the capacitive coupling through the can to the inner coil, provides a path to charge the capacitor faster than the 1 legged AV plug alone.

It provides very good spark and relatively no heat from the neon transformer nor the ign coil, as compared to running the coil via points setup. Tesla's igniter for gasoline engines(pat) is also a more efficient way to drive the ign coil than standard points setup.

Im using SIDAC's as a solid state spark gap, 2 in series, for the capacitive discharge.

http://www.youtube.com/watch?v=TR3WmK3qrws

Mags





poynt99

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Re: Ignition Coil Won't Spark from Mosfet but DOES spark By Hand??? HELP!?
« Reply #6 on: February 19, 2012, 06:43:00 AM »
pha3z,

Two possibilities that may be snuffing out your spark are:

1) Too low of a MOSFET OFF resistance
2) The MOSFET body diode is zenering or avalanching.

.99

Johan_1955

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Re: Ignition Coil Won't Spark from Mosfet but DOES spark By Hand??? HELP!?
« Reply #7 on: February 19, 2012, 10:24:57 AM »
Hi,


Would be good to take the Series Diode from the HV-Coil away, is keeping him away from the needed ringing, make sure Duty-Cycle is 50/50.


Regards, Johan

TinselKoala

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Re: Ignition Coil Won't Spark from Mosfet but DOES spark By Hand??? HELP!?
« Reply #8 on: February 19, 2012, 02:32:27 PM »
No they are not.

And don't ask me questions nor tell me what to do.
Also, let the man himself decide who's being helpful and who's not.
If you are here to argue do it with someone else.

You are the one who is arguing. I am providing FACTS and REFERENCES and SUGGESTIONS to help the OP achieve his goal. I even illustrate that what I say is true by DEMONSTRATING that it is true.

Why don't you provide a reference that says the pulse-forming transformer in a CDI system is an ordinary ignition coil? Why don't you provide a video or two showing your excellent experimental work? Don't ask you questions? Don't tell you what to do..... when you are telling me what to do?

OK, fine. You clearly know more about this stuff than I do, with your two or three posts on the topic.


@Johan: I encourage you to experiment with the circuit, with and without the diode. Have lots of spare 555 timers when you do.

Here's what a properly switched mosfet coil sparker can do--- of course the component count is a bit larger and a bit more skill is involved here than in the simple ignition coil. One reason this works like it does is because --- like a flyback transformer and unlike an automotive coil, there is no heavy iron core and the coil is driven at its resonant frequency. Don't watch this, microcontroller, it will probably upset you.
http://www.youtube.com/watch?v=LFDjZ_Va9xg

Johan_1955

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Re: Ignition Coil Won't Spark from Mosfet but DOES spark By Hand??? HELP!?
« Reply #9 on: February 19, 2012, 07:45:49 PM »
Hi,


@KookooDiesel: For Diesel savings, please look at: http://www.youtube.com/user/OostromTechnicsSL ,  based on:


@TK: For a good spark you need to the right coil related Pulse-Width, Mag & De-Mag times to get the right induction / Spark, so a PWM frequency driven is false, you need a fixed Pulse-Width (50/50) and a adjustable frequency.


This is my back ground and at that time, with Krüber and Motoplat ignitions: http://www.youtube.com/watch?v=DKDo-XkUfos


Regards Johan

WilbyInebriated

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Re: Ignition Coil Won't Spark from Mosfet but DOES spark By Hand??? HELP!?
« Reply #10 on: February 20, 2012, 02:36:11 PM »
tinsel koala... the perfect blend of sophistry and moronic that gives us the word sophomore; the pretender to wisdom.

fritz

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Re: Ignition Coil Won't Spark from Mosfet but DOES spark By Hand??? HELP!?
« Reply #11 on: February 21, 2012, 08:24:28 PM »
Your coil is perfectly right.....

A typical ignition coil is designed for a max of 8000 rpm´s.
With a four-stroke engine  you will get  an ignition per revolution.
So the maximum rated frequency is 133 Hz (!!!).  so not even kHz.
So it fires every 8ms.
To achieve the maximum performance - there will be about >5ms to "load" the coil and the rest for the spark _(if not even more loading time)

The amount of voltage applied vs. time vs. inductivity gives you the energy stored in the coil.
This energy is released on turning off.
If you operate the coil with 100khz instead of 133Hz - you would need about more than 800 times more voltage to get the same charge in.
Instead of 12 V you would need 9000V switched to get the same energy.
But your coil ist designed with isolation restricted to somewhat beyond ;-))


http://en.wikipedia.org/wiki/Inductance

The lower the frequency and the longer you switch in the current - the more energy you get into the coil. This is just limited by the ohmic resistance of the copper.
With charging time about 1s - I remember sparks of 2-4cm from an ingnition coil.

With 100kHz and 12V - there will be no ignition coil at all to produce useful sparks.








TinselKoala

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Re: Ignition Coil Won't Spark from Mosfet but DOES spark By Hand??? HELP!?
« Reply #12 on: February 23, 2012, 05:47:34 PM »
Are you folks not able to watch the YT videos I posted of my IGNITION COIL making 3-4 cm HOT ARCS on the small Jacob's Ladder, using 12 V input and a 555 timer switching a power transistor??

I think it's hilarious that people are telling me all these reasons why I can't be doing what I'm doing. I even publish the schematic, ffs. But what else do I expect from this forum. Nineteen threads discussing things that can't possibly work or be useful in any way, and this thread.... where I am apparently doing the impossible, according to you.

And of course there's my own personal troll, who follows me everywhere like a sick puppy dog, and still is worried about which MOSFET I used debunking Ainslie years ago -- but has not made a single comment about her revealed error which totally invalidates all her claims.