Need Help making a DIY timing light

Thread Starter

ateliersoma

Joined Nov 20, 2018
4
I want to build a timing light like this https://www.ebay.com/p/Car-Motorcycle-Ignition-Timing-Light-Gun-Inductive-Xenon-Tester-Auto-Engine-Tool/2096901646 for testing vehicle's ignition timing. So basically, it works by plugging red and black clamps to the battery positive and negative terminals respectively and the third clamp (the big square clamp) will be latched to the high tension wire of the vehicle spark plug and whenever that sparkplug fires, the timing light will turn on as in this video

I'm wondering if a DIY of such tool is possible and what will be the components for the project. The hard part I guess will be the clamp that picks up signal from the spark plug wire. So far, I have found 2 possible schematics which are quite different: https://imgur.com/Uz81Mfb from http://citroen.tramontana.co.hu/en/ignition/stroboscopic-timing-light or this https://imgur.com/dhGSf0L where a 555 timer is used and the pickup sensor is a ferrite core looped with 250 turns of 28 gauge copper wire.

I don't know much about electronics so I don't know which schematic will be more suitable.
 

drc_567

Joined Dec 29, 2008
714
In the first circuit shown, the energy that triggers the thyristor gate, thus turning on the LED, comes completely from the inductively coupled pick-up clamp. Consequently, the clamp will have to be relatively efficient and have a correct orientation for the thyristor to fire. Note that the trigger path does not connect to the DC circuitry from the battery ... There is no dot where the trigger wire crosses with the R2 resistor wire, so they are not physically touching or connected.
 

Thread Starter

ateliersoma

Joined Nov 20, 2018
4
In the first circuit shown, the energy that triggers the thyristor gate, thus turning on the LED, comes completely from the inductively coupled pick-up clamp. Consequently, the clamp will have to be relatively efficient and have a correct orientation for the thyristor to fire. Note that the trigger path does not connect to the DC circuitry from the battery ... There is no dot where the trigger wire crosses with the R2 resistor wire, so they are not physically touching or connected.
Thanks for the feedback, in this schematic diagram https://imgur.com/Uz81Mfb, what does the hollow hole near the trigger port mean (encircled in red) and is C1 capacitance supposed to be 22pF? (listed as 220 in the figure)

So in theory, it will work as long as the trigger clamp is appropriate?
 

DickCappels

Joined Aug 21, 2008
5,884
The coiled part is a capacitive pickup. You can use five to ten turns of a small gauge wire around the high voltage lead, don't over-do it. You should also be able to use a small spring loaded clamp like a clothespin (remember those?) to hold a small piece of metal against the high voltage lead. A few square cm should be more than enough.
 

DickCappels

Joined Aug 21, 2008
5,884
Thanks for the feedback, in this schematic diagram https://imgur.com/Uz81Mfb, what does the hollow hole near the trigger port mean (encircled in red) and is C1 capacitance supposed to be 22pF? (listed as 220 in the figure)

So in theory, it will work as long as the trigger clamp is appropriate?
upload_2018-11-20_16-13-2.png

The loop ("hollow hole") represents a shield. The trigger input is in a shielded cable.

"So in theory, it will work as long as the trigger clamp is appropriate?[/QUOTE]". In theory, yes.
 

drc_567

Joined Dec 29, 2008
714
220 uF doesn't seem right. As you suggest, try 22 pF or maybe 0.01 uF.

Another variation to experiment with would be to pick a ferrite core large enough to hold the windings, then remove a 'slice' of the ferrite ring perimeter large enough to insert the #1 cylinder wire, then replace the ferrite ring slice, so as to have a continuous magnetic loop. A narrow Dremel carbide cutting disc should do the job. Use a small permanent magnet to hold the slot piece in place.
 
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