Splitting an ignition coil output

Thread Starter

Jerry Dziuba

Joined Feb 18, 2016
28
I am using an automotive ignition coil to generate a spark to ignite a pilot for gas combustion. In certain combustors we are using a split grid for two different gas sources and were wanting to supply this split grid with separate pilots and were hoping to be able to power the igniter rods from one coil. Obviously just splitting the coil output line to two igniters will not work as only the one with the least resistive path to ground will spark.
Can anyone think of any possible solutions other that a manual switch to physically connect/disconnect the ignition line to each pilot and light them separately?
 

AnalogKid

Joined Aug 1, 2013
8,251
Not unlike the problem in every gas engine built since 1910, and they all have the same solution - a rotary switch called a distributor. I think it is possible to drive two ignition coils from one exciter circuit, but I've never tried it.

Depending on how much spark energy you need, there are small 15 kV boost converter modules on ebay for very low cost. Two of them probably are smaller than a single automotive coil.

Hypatia thinks 100 kV is a light breakfast; maybe he has a trick to share.

ak
 

crutschow

Joined Mar 14, 2008
24,081
Besides the one DD noted, there are a many other dual output coils available that are used for wasted-spark ignition systems.
Basically instead of one end of he secondary going to ground, as with a standard coil, the dual output coils bring out both ends of the winding.
Thus the spark goes through both spark gaps in series at the same time.
The output voltage just has to be high enough to ionize both gaps (to the coil it looks like one gap with double the gap length).
 

Hypatia's Protege

Joined Mar 1, 2015
3,203
Can anyone think of any possible solutions other that a manual switch to physically connect/disconnect the ignition line to each pilot and light them separately?
Yes, of course --- Merely place the gaps in series:cool: --- Note that said scheme may be readily realized via use of a 'floating secondary' coil as described in post #4:)

Best regards
HP

PS --- FWIW applicable coils were/(are?) employed on many GM V6 engines over the past 20+ years (e.g. Olds, Buick, etc...)
 
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Thread Starter

Jerry Dziuba

Joined Feb 18, 2016
28
Thanks for the heads up about the dual output coils everyone, I never knew they existed.

I am curious about what HP meant with "Merely place the gaps in series", if indeed that was a serious comment. I'm not sure I'm comprehending the idea there.
 
Thanks for the heads up about the dual output coils everyone, I never knew they existed.

I am curious about what HP meant with "Merely place the gaps in series", if indeed that was a serious comment. I'm not sure I'm comprehending the idea there.
--Emphasis added--
But that's precisely what said scheme is doing -- You may visualize the electrical circuit as follows:

CoilEnd1 → Gap1 → Common → Gap2 → CoilEnd2 Got it?:)

Note that 'Duel output' is a misnomer -- The HV winding of such a coil is merely a floating, isolated, secondary -- hence the 'output' terminals are attached to opposite ends of the same coil...

Best regards
HP:cool:
 
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Thread Starter

Jerry Dziuba

Joined Feb 18, 2016
28
Got it! Thanks. While it does give me two sparks actually implementing it in the design would be a bit unwieldy I'm afraid. So we have a dual output coil on the way and hopefully that will fit the bill nicely.

Thanks again to everyone for the heads up on those, if it works out it will hands down be the easiest of all the possible solutions we've been experimenting with to date.
 
Got it! Thanks. While it does give me two sparks actually implementing it in the design would be a bit unwieldy I'm afraid. So we have a dual output coil on the way and hopefully that will fit the bill nicely.

Thanks again to everyone for the heads up on those, if it works out it will hands down be the easiest of all the possible solutions we've been experimenting with to date.
There seems to be some misapprehension -- The circuit described in post #11 is the scheme of a so called 'duel output coil'! As stated above 'duel output' coils arent truly 'duel output'... -- The good news is that it will work fine so long as the gaps/igniters share a common ground... --- If that's not an option, the next best solution is use of two (co-excited) coils each referenced to the the return of it's respective gap...

Best regards
HP
 

Thread Starter

Jerry Dziuba

Joined Feb 18, 2016
28
Ah, I got you now! I actually used a "single output" coil and ran a common wire between gaps and then to ground. But I see that in the "dual output" the coil acts as the common link from opposite ends.

Thanks for the clarification. Helps my understanding and yes, they will be sharing the same case ground so it should work fine.
 
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