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Topic: Another photo flashgun question (Read 549 times) previous topic - next topic

evilvet

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.



retrolefty

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

evilvet


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


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

retrolefty

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


AWOL

MOC3020 opto triacs are cheap and simple, and don't mind which way round you connect the flashgun, unlike opto-Darlingtons.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

evilvet

Fixed it

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

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