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Flip flop to reverse switch?

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hogshead

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I have an old fashioned distributor that fires a strobe as the points of the distributor being tested open. I want to test a four contact rotary switch (a model T Ford timer) so that the strobe fires when the switch closes. I tried a conventional relay, but the point bounce caused multiple firings of the strobe. My thought is a flip flop that will open when the switch closes and stay open for 20ms or so. Can someone point me in the right direction?
 
Wouldn't a modern inductive pick-up timing light work? A spark is a spark is a spark!
 
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Mike, I don't see how. There is no high tension. Just switching action. I am trying to test a low tension switch. I want to be sure that it is turning on every 90 degrees exactly whilst turning 1500 rpm or so.
 
Ok, but doesn't the strobe rely on the inductive kick from the coil primary? Are you sure the strobe fires on just a clean 6 to 12V square wave?

Personally, I would just use my oscilloscope.
 
I'm not sure exactly how the strobe works. It is inside the machine and uses a neon light to illuminate a rotating white arrow that points to a degree wheel. This machine was built in the 40's (has tubes). As I recall it has a 5U4, which is a full wave rectifier, I presume to supply DC to the neon light. I don't know how it uses the opening of the points to trigger the neon light though. There may be another triode or something. Sorry, it has been years since I've cracked it open. OK, so how would you do it on a scope? At any given speed I can get four ugly square waves. How do I know that they are 90 degrees apart? I have a 4 channel scope, although maybe 1 or 2 is enough?

My preference would still be to make a circuit to mimic the opening of points by the closing of the switch.
 
Ok, then let us back up. It is not a switch that triggers the strobe, it is the voltage that appears across the switch that does it. In a points ignition system, it is likely the low-to-high edge of the voltage across the points as the points open that does it. The rising voltage occurs because the coil is powered from the battery, and the points provide a path to ground, where the ignition event occurs just as the points open.

I have no idea what the model T timer does. Is there a battery involved?
 
First off Mike, thanks for your interest in this. You may be correct as to how the strobe is triggered, although I don't think that you are. If an inductor were involved the strobe timing would retard as the speed of the machine increased due to the fixed lag time to ramp up the coil. I think the falling voltage triggers a tube amplifier circuit. The plate of the tube drives the strobe (I presume).

A model T timer is a rotary switch driven off of the camshaft at half engine speed. Instead of producing a spark when the connection is broken, it completes a circuit to a relay. When the points on the relay open the field collapses and the spark occurs. On the Model T there is no battery involved in normal operation, the current is supplied by an internal permanent magnet AC generator (alternator) that is indexed to the crankshaft. The timer actually acts as a mechanical rectifier (commutator) and picks off a half cycle of the AC potential. The coil then fires when the current rises to a preset level (about 3 amps typically). Because the coil fires at this preset level, the coil will usually fire at the same point on the AC waveform regardless of speed, thus keeping the timing steady as the engine speed increases.

All of this has nothing to do with the problem at hand. I want to test the accuracy of these timers on my old fashioned distributor tester. I want to spin the things up and see four arrows 90 degrees apart, just as I do with a four cylinder distributor.
 
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