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ken collins

Strobes

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I got a couple variable speed 25 watt cheap strobes I want to fire off a controller via a relay. I removed the scr from the ckt board, shorted the gate to either the anode or cathode, and hooked a couple wires to the anode and cathode, thinking when I touch the wires together, the strobe would fire. wellll, that didn't work. any suggestions?

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How certain are you that you have the three leads correctly identified? Haven't seen the circuit, but I would expect that leaving the gate floating would be the best option.. Note that you are probably playing with what could easily be 170 to 350 volts on those leads, so you are definitely playing at your own risk...

I would also caution that some fixed rate strobes may easily charge capacitors over their rated voltage if they don't fire as often as in their original design.

Personally, if I were doing it, I would look at keeping the original SCR in there, and adding an optocoupler SCR in series with the gate. Install the optocoupler and current limiting resistor inside the strobe, with good insulation on it, and then you are not bringing any high voltage outside the strobe case, and you can use a DC card channel to safely trigger the strobe..

But, at these voltages, you did not hear it from me! shock.gif

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ken collins wrote:

I got a couple variable speed 25 watt cheap strobes I want to fire off a controller via a relay. I removed the scr from the ckt board, shorted the gate to either the anode or cathode, and hooked a couple wires to the anode and cathode, thinking when I touch the wires together, the strobe would fire. wellll, that didn't work. any suggestions?
Ok, you removed the SCR from the strobe? Lets say that you are refering to the SCR on the strobe. Now you say that you shorted the gate lead to one of the other two leads of the SCR socket. What is this suppose to do for you? If anything, leave the gate lead floating. I do agree that you are playing with very high voltages, in the order of several hundred volts. Can you say tazer?

With out getting a look at the circuit I am hard press to say what is going on. But with the gate shorted to the anode or cathode, maybe you are dumping the charge to ground. Once the gate is floated, I would think that the unit should fire. As for the cap over charging. Most circuits are built to supply only so many volts. And a good circuit will be rated to only built to a value less than the WVDC of the cap.

Please my friend be very careful will working on a strobe. That cap can sit you one your arse, or kill you.

Max

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I've sort of thought about changing some fixed rate strobes to remote trigger.. However, the cap that fires the trigger coil is not rated to the same voltage as the source that charges it. The reason it is not an issue is that the voltage on that cap is applied to a neon tube that breaks down and conducts through a series resistance to the SCR gate before the rated voltage on the cap is exceeded..

So in this case, if you just replaced the neon lamp with a SCR, and failed to trigger at least as often as the original design, you could easily charge the cap beyond the rated voltage...

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I got the info for this off the "ChristmasinKent Web site. I removed the scr and put wires in the ckt board where the scr was. I essentially shorted all three terminals together,(being very careful). I was just taking a break from building kits, and thought I'd try, and see what happens. Just happen to have seven of these floating around, and thought I'd put em to use. Thanks for everyone's input and especially the safety notes. I was aware of the caps and the high voltage potential.

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Thanks for everybodys input.. Did finally get back to this project tonight with an optocoupler. Worked like a charm.. Thanks klb, sparky, and Jeff and max-paul

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Hi Jeff, gonna use em as a shooting star effect. Wanted something brighter than a curtan strobe, or rope light. Although now that I have it figured out, the mind is wandering..... Thanks again for everybodys help. Ken

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