i've purchased a few of these with the intention of using them to interface my arduino with the power button of a point and shoot canon camera. i breadboarded everything out, it worked, then i soldered it together. no go!
i'm going back to the breadboard phase before another effort at soldering. are there any known vulnerabilities of the opto-isolators? the circuit is simple - 5v from pin 12 to activate the opto-isolator.
thanks
There should be a series resistor installed between the Arduino output pin and the anode connection to the opto input LED and of course the cathode of the opto LED would then go to ground. The LED current must be limited to 20ma or less. You may have degraded the input to the opto device by not having the resistor installed.
Lefty
what size resistor is needed?
(hey, i wasn't kidding when i said newbie. i do appreciate the explanation.)
Anywhere in the 200 to 400 ohm range should work OK, 330 ohms is a standard value.
Lefty
The problem with this is that cameras don't always have a simple pull to ground connection. Some have the switch embedded in a scanning matrix in which case the signals could be bidirectional. This means you might have to go to an analogue switch like the 4051 to get it to fire.
Also most cameras have a two position push switch, the first focuses the picture and the second takes the photo. This is in effect two switches.
You have chosen quite a complex project for a beginner.
Some have the switch embedded in a scanning matrix in which case the signals could be bidirectional.
interesting! i never considered something that complex.
then again, i already tested this when it was bread boarded.
i think i may have made circuit changes when fitting it to the circuit board.
Also most cameras have a two position push switch
I'm triggering the shutter via software, CHDK.
You have chosen quite a complex project for a beginner.
It certainly feels that way at the moment. Still, I think victory is right around the corner. I'll have to post my results here.
many thanks!
does anyone have a short(ish) answer on how i could have known that the resistor was necessary from the specs? and what size resistor?
I've started reading the Naval Electrical Engineering Training Series but its going to take me quite a while to pull an answer to my questions out of it.
Yes, the data sheet for the optical isolator will state the design current specification for the internal LED as well as the forward voltage drop developed by the LED. With that information and knowing the source voltage of the Aurduino digital output pin one can calculate the needed resistor value using R= (Vhi-Vfd) / I
Lefty