Design for Dashboard Timing Advance Meter

I love it!

On something a bit more modern I'd even argue to make it adjustable, but I suspect wrong vintage for that.

Good luck!

Well thought out SSCpal.

Seems you may have answered your own original posting from last month

http://cr4.globalspec.com/thread/73618/Dashboard-Timing-Display-for-Hot-Rod

Let's know how it works out.

I'll give you a GA if you add a comment here.

Thanks, Wal. I'm an amateur circuit designer, but had most of these parts laying around the bench, so that was my guideline. I'm going to assemble an ignition system simulator on a board (have those parts too) to optimize the firing detector circuitry and go from there. I have a "knock detector" I got on eBay that I've never used, and may incorporate that somehow to correlate it with advance. Add a datalogger to my laptop and have a record of things that go bump in the night.

Enjoy!

Using capacitive coupling to plug cable won't be too time reliable since you will have to use high impedance and gain amplification, steep low pass filter to reject the coil oscillations and that would ruin the timing information. Plus on a braker point ignition it will also pick contact closing. Clamping diodes must also be very fast to provide any protection to cirquit on the slightest HV leak. I 'd prefere passing the plug cable through a torroid core (possibly dividable), winded with a few ground referenced turns. It's a common way to sense current, (variations are used in AC clamp meters and timing light guns) and it's safer, plus it will only pick actual spark current pulse. And all this if you can't get your timing from low voltage side. S.M.

Yes, the firing signal is the part I'm least sure about. The core is a good idea. When I get my ignition simulator built, I'll try some different things and look at the signals on a 'scope. Thanks for the thoughtful input.

I've got the meter movement hooked up and have a small problem. The pointer doesn't move until about 5ma. So I need to somehow bias it to move as soon as we have an advance signal. Any ideas?