External trigger question

[Petros Nousias]

Im building an external trigger that will be connected to a computer. I'm using an optocoupler(4N32) and aparently it shows a resistance of 16kohms in the output. Would that affect the camera in any way?

 

[xldaedalus]

Resistance doesn't mean anything. A 4N32 has only 4 pins you care about. On your side(MCU control side), you need >3v and 10mA to DIODE ANODE + and DIODE CATHODE - turn on the transistor side, RED TRIGGER to COLLECTOR + and EMITTER - to ground. The only resistance that's important is the ON resistance between Collector and Emitter. You can get +12v from the serial port and +5v from the parallel port, or if you're using USB, you need an MCU that will read an USB byte and HIGH a pin to power the relay/4N32

With a 4N32 you need a minimum of current in the RED trigger line to overcome the ON resistance of the 4N32. And, in order to work properly, the 4N32(your computer) and the RED may have to share the same ground, this is not so with the relay if the trigger pin has two wires + and -.

The RED ONE trigger line may not have sufficient current to conduct properly, esp if it gets hot. For my camera trigger circuits in which the trigger line is looking to be LOGIC LOW, I use both an 4N32 and an SMD 5v powered relay in parallel to connect the trigger line to ground. The reducancy is to protect against failure

The SMD 5v relay uses more current than a 4N32 alone, but it works EVERY TIME, but, since its mechanical, it has a limited life, depending on the quality you buy - 100,000 to 5 million cycles ON/OFF.

You only need to be sure that the RED TRIGGER is looking to be pulled to ground and which of the two wires is + and which is -(ground)

I don't know this, but I would like to know myself, as well as, if the RED has an external trigger connector, what type it is and what the pin out is. If you find it, can you post it here? Thanks.

Lee
mocoman.com

 

[Petros Nousias]

Wow, that was a thorough reply! First of all, the resistance reading I took was wrong since the emiter and collector pins were connected directly to the multimeter and not in series with something of a known resistance value, so even though I didnt try it I'm sure that in this case it should fall into the 100-150 ohm area... Still I wonder if this should be damaging in any way to the camera. A mechanical trigger is out of the question since I will be using it with a motion control head I'm building so I need accuracy that a relay can't provide.
I dont know if I understood your question regarding the external trigger question. The one Im using is the 12v accessorie shoe. Its a lemo with part no. FGG.0B.304.CLAD42Z(that's the male plug, not the camera one). the pin out is:
1. -VOUT Auxiliary power return (Ground)
2. GPI Trigger
3. GPO Tally
4. +VOUT Auxiliary power output

In the case of the 4N32, the collector would go to 2, and the emmiter to 1.

 

[CVB]

The external trigger is on the rear aux IO connectors. Its a no-go for doing motion control unless you're doing timelapse at very slow frame rates (<6FPS). As for the triggering mechanism for use with a PC, have a look at the AQY21 photomosfet... it acts just like a relay but its completely solid state. Just make sure you put a current limiting resistor on pin 1 to keep the internal led from making magic smoke.

 

[Petros Nousias]

Im not looking for a frame by frame accuracy, just an on/off function.
Thjanks for the photomosfet tip, ill give it a try.