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Author Topic: Another photo flashgun question  (Read 417 times)
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Melbourne Australia
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Hi all

I am trying to trigger a photo flash gun that simply requires the short of the pins on the hot shoe.

The circuit I am using is based on the Uno driving a 6N138 optocoupler. An LDR paired with a 10k resistor and a laser pointer gives me a range of values on A0 from 500 to 950 when the beam is broken

This code

int sensorPin = 0;
 int sensorValue = 0;
 int cameraTrigger =  13;

 void setup() {
   pinMode (cameraTrigger, OUTPUT); }

 void loop() {
   sensorValue = analogRead(sensorPin);
   if (sensorValue > 900) {
     digitalWrite (cameraTrigger, LOW);
   }
   else
   {
     digitalWrite (cameraTrigger, HIGH);
     delay(500);
     digitalWrite (cameraTrigger, LOW);
   }
 }

Seems to work fine, pin 13 goes high just as expected and when I add an LED as a test as per the attached PDF, it does just what I expect it to do.

I cannot work out how to wire in the flash gun, it is just two leads that when shorted fire the flash.

Any advice much appreciated.



* tCad1.pdf (31.34 KB - downloaded 10 times.)
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Left Coast, CA (USA)
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Quote
Any advice much appreciated.

Everything you even needed to know about flashguns. Including different flash trigger circuit suggestions way down the document. Basically it is a two terminal interface what has to have a 'standoff' voltage rating => then the flashes hotshoe voltage.


http://repairfaq.cis.upenn.edu/Misc/strbfaq.htm#strboaof
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Any advice much appreciated.

Everything you even needed to know about flashguns. Including different flash trigger circuit suggestions way down the document. Basically it is a two terminal interface what has to have a 'standoff' voltage rating => then the flashes hotshoe voltage.


http://repairfaq.cis.upenn.edu/Misc/strbfaq.htm#strboaof

Thanks but I don't need a flashgun circuit, I simply need the optoisolator to act as a very fast relay, when D13 goes high the other side of the gate has to close fast and stay closed only as long as the pin stays high
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Search that link for the section:

"Optoisolated Remote Trigger from low Voltage Logic or Signal"

It covers what you said you needed to do in the start of this post, to trigger a hotshoe strobe.

Lefty
 
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I don't think you connected the grounds, Dave.
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MOC3020 opto triacs are cheap and simple, and don't mind which way round you connect the flashgun, unlike opto-Darlingtons.
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Fixed it

SY4090 SSR did the job perfectly with a 150o resistor as a current limiter.
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