Breaker points triggered transistor ignition

[cmanson123]

Help I need help building a circuit that can be triggered by the points sytem in my tractor that uses a 12vt coil. I am planing on using a gm hei coil off of a 86 cavalier twin posts,aka waste spark, that has a coil resitance of .33 ohms.

 

[MikeMl]

You want to retain the points and not modify the distributor?

Is the dwell requirement for the HEI coil similar to the original coil? (I dont know, but I think not)

 

[shortbus=]

Here is what you need. even though the are using it for a motorcycle it will work on anything with points and a 12V system. Put a new set of points in when converting and you will never need to change them again. **broken link removed**

 

[cmanson123]

Thanks i built that circuit and it is for a min coil ohm rating of 2.3 ohms as i stated the coils i am using is .33 ohms i have blown three modules with that circuit with the module mounted to a computer processor heatsink the first on i built ran for about 30 min . I figured a bad module secone one not good heat sink third never even made it past bench test.
I also built this circuit **broken link removed** using a slight ly diffrent igbt only rated at 410 volts this circuit the trigger transistor fires once the second time i try it it shorts triggered and transistor is no good...help agravated and distgusted /

 

[cmanson123]

i'm not sure about the dwell specs but being the coil has lower resitance i'm sure the dwell is going to be diffrent

 

[shortbus=]

Add a 2Ω resistor between module and coil. This will give the needed resistance to make the module live longer. Or get the module that goes with that coil. The dwell is controlled by the points.

 

[MikeMl]

...The dwell is controlled by the points.

Yeah, but the electronic ignition modules frequently require a much different dwell compared to a coil.

 

[cmanson123]

Shortbus I tried adding the 2ohm resitor to the grounding side before the transitor neg side of coil but it didn't seem to allow the engine to run and i know i should be able to build a better circuit than that one for less i just can't seem to think of the componets to put together in the right sequence.

 

[cmanson123]

Yes mike I would like to retain the point because it's just a twin cylinder onan and has no distributor

 

[shortbus=]

@cmanson123 - Have a look at these circuits - https://www.5bears.com/tim4.htm

On the GM modules, are you mounting them to a heatsink of any kind? Even a piece of aluminum sheet metal will work.

 

[debe]

Using points you need to use the HEI circuit in Fig 4 with time out, this will protect the module if the engine stops with the points closed. If its an Onan with ign coil with 2 HT leads, just use a GM coil the same which should suit the HEI module.

 

[cmanson123]

I built that circuit with the time out and used a pentium 3 heatsink for the module still blew out I don't know what to do those module cost 38 bucks is there a cicuit like the gm module one with a better transisotr that can handle more amperage?

 

[cmanson123]

WELL LADIES AND GENTS,I have built the circuit using a ford igniton module mounted on a pentium 3 heatsink and it works wonderfull. So i guess if you want something done just continue to search the internet till u find it yourself. Thanks for all the help that you people supplied and a few of them might of worked. I really would of prefered to make my own but when in rome. https://www.advrider.com/forums/showthread.php?t=417099

 

[debe]

Thanks for that info, I have stacks of those TFI modules & never realised they worked with Points.