Help Designing an Ignition Coil Tester

[debe]

You are right the LED is drawn wrong way around. Theres plenty of 2SD1071 transistors on ebay at reasonable prices Ive bought about 20 of them some time ago for ignition modules. You could also use BU931P or BU941 or any other Ign switching transistor that has internal protection diodes.

 

[dr pepper]

I use a current clamp to test coils in vehicle, a good thing to have on that unit would be a sense resistor between the fet and gnd, then you can 'scope the current waveform.

One of the most common failure modes of a coil is shorted truns in the pri or sec, this is easily noticed on the current waveform, as instead of an oscillation followed by a steady current increase through the inductance of the coil from zero, the current steps from 0 vertically to somewhere part way to full coil current.

 

[debe]

Thanks for that suggestion dr pepper, will add that feature.

 

[milkoni]

Thanks to all!
Very useful information!
For my project I found a new information. Two ignition Coils are connected in parallel but with opposite polarity. This means that the output voltages of each coil are out of phase or opposite to each other (when one is positive, the other is negative).
Is this mean that I have to test 2 coils together, or a single coil?
In the attached file 791 to 794 are the ignition coils.

 

[dr pepper]

debe 0.1r 10w ought to do the trick.
Then you'll get 1v per 10a.

 

[debe]

milkoni, personaly I would test each coil individualy. I go to the wreckers here & salvage various conectors that plug into coils, to connect the tester.

 

[shortbus=]

Wouldn't it be faster and easier to use a GM or Ford ignition module and a 555 timer to make a coil tester?

 

[ClydeCrashKop]

I happen to have an ignition module from a 1980 Nissan.
What kind of input does it want?
Is that pickup coil hall effect?
How would I interface a 555 or Arduino to it without hurting it?

 

[shortbus=]

Don't know about that one, that's why I suggested GM or Ford. Although the pickup coil kind of looks like a GM, and they give a low voltage output as each of the reluctor wheel teeth goes by.

 

[debe]

Yes Clyde you can drive the IGN module with a 555. In the circuit I posted just substitute the transistor with the module & it will work fine.