A new ignition circuit

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dsage

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BTW.
Perhaps it wasn't clear, but you can connect your points to the input instead of the hall sensor. The hall sensor and magnet works like points i.e. normally high input going to ground when active.
Eliminate the capacitor / condenser that it typically across the points on your engine. It is not necessary and will cause issues.
 
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I have bult 3 of these but this is the first one I've used with points. No condenser used. The led comes on and it fired when the points close for sure and went out but didn't fire when the points openied when I was trying to set the timing last night. You have to barely turn it to set the timing so the lock out may be the problem but how do you get around that. The parts are as specified and built on the same PCB board as the others so I dought wiring is the problem but I will build another today just in case. BTW thanks to everyone involved in designing this. Bob
 

dsage

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When you turn the engine over by hand it may "appear" that the spark is occurring when the points close (the LED lights). In fact when it is operated so slowly the timeout is triggering every time. The timeout is only about 15 mill-seconds (I think) after the points close (the LED turns on).
So what you see is the LED go on, the timeout happens and the timeout will issue one spark before you can turn it enough for the LED to go out. Once triggered (by timeout or otherwise) it will not generate another spark until the cycle repeats.

You can set your initial timing using the LED. The led follows your points operation.
Use a degree wheel or degrees marked on the flywheel with a TDC mark reference. A timing light will be of no use turning by hand because of the timeout spark triggering it
Turn the engine over by hand and watch the LED go ON. Ignore the spark and keep turning until the LED goes OFF. Set your timing according to the marks.
Just set it roughly. You can use a timing light once the engine is running.
The 15ms timeout is a non-issue when the engine is running.
Unless like I said, you have a very slow running single cylinder engine. Typically a full sized hit-miss.
You should also check and adjust the dwell degrees of the points. Most hit-miss engines have excessively large dwell time (points closed time). This is just a waste of power and overheats the coil keeping the coil charged for more than the 6ms or so it takes to fully charge it.
 
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dsage

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I never envisioned the timeout being an issue. And it hasn't been. The circuit could have been designed for a several second (or longer) timeout. Something more in line with times that might actually damage a coil should it stay energized.
But that would require more circuitry than the driver itself. The point was to keep the circuit as simple as possible. Tradeoffs are always in play with circuitry.
As mentioned C2 can be increased a bit if you get kick-back from a large single cylinder engine when pulling it over by hand. But the LED starts to act funny if it gets to be more than a few microfarads.
Decreasing the dwell is an all round better solution.
You can do the math for your engine minimum rpm / dwell time etc.
 
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