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Old Aug 3, 2005, 9:55 PM   #11
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Geriatric,
Since you like to keep things simple:G, I suggest this modification to your circuit:
Add a capacitor C and a resistor R:
At the closing time, the inrush current will charge C and fire the led inside the opto-coupler for a brief moment, just enough to fire the external flash.
Then the current drop to near nothing (leakage current) and at the same time "disarm" the SRC (or triac) of the camera hotshoe circuitry, make it switching to open state.
The resistor R will then do the job of draining C, making it ready for the mext "charge" initiated by the camera hotshoe SRC again.
For calibration purpose, I guess that C should be around 10 to 47 micro-F, R may be in the 100K range.



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Old Aug 3, 2005, 10:23 PM   #12
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thanx for the new improved circuit. now can i use this circuit in the flash itself , doing so i can take power from the flash battery pack and no need of 2 AAA battery. it would be around 4.8-5v wich i think is not harmful.
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Old Aug 3, 2005, 10:56 PM   #13
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tilgates wrote:
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... so i can take power from the flash battery pack and no need of 2 AAA battery. it would be around 4.8-5v wich i think is not harmful.
In this case, you better isulate the pin 4 and 6 from other connections , ie: connect pin 4 and 6 to the external flash (vivitar) trigger connections only, but do not connect pin 4 to battery negative anymore.

Good luck
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Old Aug 3, 2005, 11:13 PM   #14
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thanx, now it means pin 4 connected to the (-)end of triggerandpin6 to(+) trigger

and which circuit should i use the doubleOptoIsolator or TriggerA
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Old Aug 3, 2005, 11:44 PM   #15
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tilgates wrote:
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thanx, now it means pin 4 connected to the (-)end of triggerandpin6 to(+) trigger
It doesn't matter since it's a triac; If you use the SRC, just switch them if needed.

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and which circuit should i use the doubleOptoIsolator or TriggerA
it's up to you:-)
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Old Aug 4, 2005, 2:30 AM   #16
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Hi

Played around with it for a bit , this time using a Fuji 4900 . Found that changing R to 1k, current flow 2.5ma. R + foreward resistance od diode worked great. Tried same on Fuji 602, no flash. Ah well back to the drawing board.
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Old Aug 5, 2005, 11:38 AM   #17
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can we change something inside the flash to lower its trigger voltage. I live in a small city i couldnt find a optoisolator IC in the market, it will take 2 days to come. in the mean time i thought if some thing else can also work
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Old Aug 5, 2005, 12:45 PM   #18
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tilgates wrote:
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can we change something inside the flash to lower its trigger voltage. I live in a small city i couldnt find a optoisolator IC in the market, it will take 2 days to come. in the mean time i thought if some thing else can also work
Try this circuit from geriatric , no opto coupler:

http://www.stevesforums.com/forums/v...mp;forum_id=53
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Old Aug 6, 2005, 1:14 AM   #19
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Hi K

You started me off using 2 AAA batteries. I have changed the PNP circuit too use these.Therefore omitting the 78L05and capacitors. The transistor resistors can be anything from say 2.7K to 3.9K. but keep them all the same value, except the emitter resistor which can be 1k to 3.9k. This will alter the pulse size to the gate . I think 1k would be about right for a pulse of 800mv. Thats what my scope says.
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Old Aug 6, 2005, 4:50 AM   #20
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thanx,

style="BACKGROUND-COLOR: #000000"im new to electronics so im confirming about the circuit

style="BACKGROUND-COLOR: #000000"1. can we use power from the flash battery pack

style="BACKGROUND-COLOR: #000000"2. i tkink 2.5mm side goes to camera and 3.5mm for the flash trigger

style="BACKGROUND-COLOR: #000000"3. i also thought of a foolish circuit im attaching it please look at it and complete it
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