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post #1 of 7 (permalink) Old 12-10-2012, 07:02 AM Thread Starter
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Ignition coil tester

Member Tasmaniablue asked about making a device to test ignition coils to see if they actually perform and create lots of kilovolts, rather than just going by resistance measurements.

On this thread, post 3:


I showed a couple of ignition coil drivers, a fully electronic one with variable spark rate, etc and a much simpler, more primitive and brutal one involving just a simple automotive relay and capacitor. I thought about making the electronic one at first, but then thought about how little use it's likely to get and decided to knock up the electromechanical one that took just 15 minutes to make.

As you can see from the photo it works rather well. I have a Bonneville 360º PVL coil hooked up to a high voltage tester which has a variable spark gap and calibrated scale (not visible on photo). The coil can be made to generate up to 20 Kilovolts reliably with this device.

The relay is a simple, cheap automotive relay with one set of on-off contacts. In use it self-oscillates at a fair rate, making and breaking the contacts and thus the current to the primary of the coil. It buzzes noisily and the relay contacts get a fair hammering, but it works well enough.

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post #2 of 7 (permalink) Old 12-10-2012, 09:06 AM
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Brilliant post Forchetto, 10/10. Possibly one of the most useful items I've seen on here. I would suggest slowing it down a lot though, to avoid hammering the relay. Try something like a 3.3uF or 4.7uF capacitor instead. You could also try switching the coil with a transistor or triac, which is a much faster cutoff than the relay.
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post #3 of 7 (permalink) Old 12-10-2012, 05:29 PM
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Thank you Forchetto. I will make one of those.........I am a bit vague on electrics so this project will be a good learning experience for me. I am pleased that my post has resulted in a device that will probably be of use to quite a few of us on this forum. BTW this forum is the best of the many that I have visited.
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post #4 of 7 (permalink) Old 12-11-2012, 12:46 AM Thread Starter
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As ripper points out, a transistorised solid-state version will be better. On this one the relay gets a right pasting from prolonged use. It only needs to be run for a minute or so to see that the coil works though, so can probably get away with it.

I have asked my technical department to create a printed circuit for the electronic version, but as usual they tell me they'll do it when "they get a round tuit". Probably something like this:

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post #5 of 7 (permalink) Old 12-12-2012, 02:44 AM
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any idea where i can get one Des.
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post #6 of 7 (permalink) Old 09-29-2013, 03:25 PM
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The question I have...and I know it is a can of worms type question...is really...How MUCH voltage...AND how much CURRENT is really needed?? is more better??

AND...while many coil makers are hyping the fudge out of their products as "Higher Output" what no one tells you is over what RPM range do these high out coils..produce a higher output?? Some coils may produce more voltage or current at low RPM's but less at High RPM'S. and some may do the opposite...

Some usefull curves and graphs of output V&I vs. RPM of various coils would be interesting...sounds like a job for DerryUK!!!!
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post #7 of 7 (permalink) Old 09-29-2013, 07:58 PM
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Could you do the same thing with a loop type voltage meter, the kind that measures load and output by placing it around a wire or cable under load?

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