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From: John Popelish
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X-Mailer: Mozilla 4.7 [en] (Win98; U)
Subject: Re: Photo Flash Trigger Circuit Help
Date: Thu, 14 Nov 2002 15:42:15 GMT
NNTP-Posting-Date: Thu, 14 Nov 2002 10:42:15 EST
> Hello John, thank you for your kind reply.
> When you say a microfarad capacitor do you mean a 1 microfarad capacitor?
> Also the SCR I am using is Radio Shack Part Number 276-1067 and the data on
> the back says:
> "DC gate trigger current: Typ. 0.6ma"
> But I guess a little extra current flow never hurt.
> The Zener is just one that I had in one of my parts boxes, I chose it for no
> other particular reason but thanks for letting me know that I can safely use
> a 1/4 watt as I do have a mind to make the circuit as small as possible.
> I will try all the modifications you have suggested and let you know how it
> turns out.
> Thank you again for your help I really appreciate it.
Yes, a microfarad means 1 microfarad. I pulled that value out of thin
air, but I think any value near that should work. The 0.6 ma gate
spec definitely means that there is no internal shunt load resistor
across the gate, but does not imply that that is the right level of
gate current to produce a clean turn on. But I think it will work
fine with the suggestions I made. Especially consider raising the
value of the 5.6k resistor, as that value will produce almost two
watts of heat, while draining energy from the strobe trigger circuit,
possibly lowering its functionality. With the capacitor holding the
gate energy, you might well get this value over 20k, reducing its heat
to less than a half watt. This will also reduce the size. Let me
know if you have any new problems with these ideas.
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