Make An LED Timing Light
Need a timing light but don't want to spend $100+?
Make An LED Timing Light From Parts You Probably Already Have
Problem: Need to adjust timing on '68 Pontiac Tempest, I don't have a timing light. I'm in a situation where most people would go out to Harbor Freight and pick one up. Me, well I'm generally not like that. I remembered one time I made an inductive ignition pickup for a tachometer on a go-kart... Why couldn't I just let that drive a few bright LED's and use it? Of course the reason that they use xenon strobes instead of light bulbs is because light bulbs glow down when you shut them off, a property that Led's lack. Making them ideal for this situation. I started with the sensing circuit which would convieniently drive about 200 mA worth of LED's. Because of the short duty cycle in this application, we are able to run our LED's way over continous current ratings, as well as the power MOSFET. The great thing about this design is that you can use any parts that closely resemble the ones I used. Nothing is very critical at all. The design is based around the 2N7000 power mosfet (my favorite) and only has 5 resistors 1 capacitor and 2 diodes. You will need; (1) 2N7000 mosfet (1) .01 uF capacitor at 50 to 100v (1) 10 ohm resistor (1) 1K ohm resistor (1) 100K ohm resistor (1) piece of perfboard or breadboard (1) clamp shut ferrite bead (1) 1N4001 diode (1) 5-20 volt tranzorb OR power zener. You will also need a few feet of wire for the pickup and some 2 conductor wire for power and lights. You can use however many LED's you want, but you need (1) more 330 ohm for every LED you use besides the first (2) which are included in the parts list. I reccomend using clear LED's because of their "projection" properties. As for color anything will work. I used red and blue because the blue LED lights at a higher bias voltage (so that the light is still functional with improper gate bias), to a certain extent of course. The schematic can be found here, LED timing light schematic

if you want to laugh at my old schematic...
MS Paint LED timing light schematic

now, some of you who are more familiar with electronics may be confused by the pickup, well... it was
just kind of an experimental thing. technically a good sparkplug wire will not make a magnetic field, and an inductor
on the end of a single wire can't transfer a current.  yeah, I agree.  BUT, it works so hey.

I think it has something to do with just a stray capacitance between the coil and the sparkplug wire, for some reason, halfway making a resonant circuit with the capacitor on the pickup coil makes it work way better.

either way, it works.

Here's a video of a version of the timing light built by Doug, youtube channel name ""
he built the circuit and came up with his own pickup design .
he uses it to check the timing on his scooter

Very Good Job!
works great!


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Sarasota, FL USA