Another question

Henry

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Dec 27, 2005, 2:25:16 PM12/27/05

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Sorry that I am being such an annoyance, but I have another question. I dont
want anyone to go through the trouble of providing an entire circuit. In
fact I want to do it myself. I just wanted to be pointed in the right
directions. What parts do I research, etc.

Anyway, here is the problem. I want to electronically trigger a photo flash
of unknown trigger voltage. The flash provides the voltage. The circuit
simply needs closed to fire the flash. But here is the trick. Photo flashes,
especially older ones, have a wide range of trigger circuit voltages. At the
low end it could be only 3.5v. On the high end it could be 300v. I have 3
flash units. (3.5v, 15v, and 55v) Although I read that there are a few old
units that go 100v and higher. Much above 5v can be death to a modern
electronic camera. So I want to make a circuit such that I can use any of
mine, and maybe other, flash unit with a electronic camera. (Either mine or
a friend's.)

So, what kinds of componets do I research that can give me the ability to
trigger a flash with a range of 3.5 to, say, 100v? I have done a search and
found high voltage transistors that can handle 200v (collector to emitter)
but still only need 5v at the base. Someone has mentioned looking into
something called an SCR. That same person suggested an opto-isolator for
best possible protection of the camera. What about a voltage regulator? (I
might be using someone else's $1000+ digital camera, so I want to be extra
carefull. Last thing I want to do is to return to them a fried camera.)

I have found sites discussing the theory of some of these components, but
they dont really give the practicle trade-offs as to when you might want to
use one verses another. Again, I am not looking for an exact circuit, just
an idea what to best spend my energy researching.

Thanks in advance,
Henry

Dan Hollands

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Dec 27, 2005, 4:23:42 PM12/27/05

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"Henry" <hen...@pghmail.com> wrote in message
news:m4ydnZ6Pmo0MDize...@pghconnect.com...

Henry

Use an optical isolator

See http://dkc3.digikey.com/PDF/T053/1570-1571.pdf

choose one with Vceo greater than 200V

It isolates your trigger signal from the flash and if you connect the plus
wire from the flash to the collector and the minus wire from the flash to
the emitter it should act like a switch which closes when you put current
thru the optocal isolator diode

Dan

--
Dan Hollands
1120 S Creek Dr
Webster NY 14580
585-872-2606
dhol...@rochester.rr.com
www.QuickScoreRace.com

Henry

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Dec 27, 2005, 7:39:00 PM12/27/05

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"Dan Hollands" <dhol...@rochester.rr.com> wrote in message
news:yhisf.56139$XC4....@twister.nyroc.rr.com...

That simple huh? ANd I was getting ready for this complex circuit.

Thanks,
Henry

deadcarnahans

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Jan 29, 2006, 6:43:26 PM1/29/06

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Decide which voltage flash unit you would like to use first. Then go from
there.

JeffM

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Jan 30, 2006, 7:08:06 PM1/30/06

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deadcarnahans wrote:
>Decide which voltage flash unit you would like to use first.
>Then go from there.

Looking at your lack of context over several posts,
I would have sworn you were a newbie posting from Google Groups
--nope--you're just a newbie who is otherwise unschooled.

FYI:
http://66.102.7.104/search?q=cache:8PaSp2kKbWoJ:www.faqs.org/rfcs/rfc1855.html+just-enough+at-*-top-*-*-message+do-not-*-*-*-original+zzz+One-to-Many-Communication+qqq+to-give-a-context

Henry

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Feb 21, 2006, 8:28:34 AM2/21/06

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"JeffM" <jef...@email.com> wrote in message
news:1138666086.4...@g43g2000cwa.googlegroups.com...

Not at all. Just a person who is doing too many projects than I have time
and resources for.

Henry