You need to know 2 things for selecting the optocoupler.1. The maximum voltage you will be switching.2. The maximum current you will be switching.Then you look in the data sheets, and find the optocoupler with a collector-emitter voltage and current that exceeds what you will be working with.
The Canon 430EX are modern flashed intended for digital cameras. I believe the voltage across the sync terminals are 8-10v, but you should verify this with a multimeter. If so you really want a transistor output for the optioisolator. Earlier high voltage flashes (200-400V) would be better served by an optoisolator that uses SCR output. The above is not hard and fast as long as the output can handle the voltage and current being used. Personally, for my Canon580EX I just use a 4066 switch to make the connections since I am not terribly concerned with the digital compatible voltage levels frying my arduinos.
...and if it's not clear yet, this is my first time to try and interpret a data sheet. So I am trying to figure out what I should be looking for, and then how to interpret that information to apply it.
Quote from: poldervaart on Jul 23, 2012, 06:39 pm...and if it's not clear yet, this is my first time to try and interpret a data sheet. So I am trying to figure out what I should be looking for, and then how to interpret that information to apply it.The voltage you listed from the data sheets is the maximum voltage that is safe for the optoisolator to switch. The one component you need to evaluate that is the voltage placed across the sync pins of the flash you want to use. The Canon 430EX you want to use has about 8-10V across its sync pins (and the current pulse is brief and not very high), so any of the optos you listed can safely handle that. When you select a transistor, you want it to have a voltage rating about 50% higher than the maximum voltage you want to switch. This margin is needed for a variety of reasons. Does that help explain?
Very helpful, Yes!So another question. Why does only one sheet list the Connector Current, if that seems to be such an important value? Or perhaps am I looking at the wrong data point for current?
For the resistor? Well, treat the input side as a normal LED (which it is - just an infra-red one) and calculate the resistor accordingly. The data sheet has the forward voltage and forward current for the LED, so use those, along with ohm's law, to calculate a resistor.
To measure the flash current you need an oscilliscope with storage