It’s the same part as the AF assist lights in my Canon 420EX flash
So I measured both the voltage and current at the LED in my 420EX flash. The voltage across the LED is 2V. The power drawn is 400mA (yes, 0.4Amps; pretty crazy, I know). The Supply voltage (with the LED disconnected) is 5.5V. That means the resistor that’s in line with the LED must be 8.5Ω.
I powered the ebay LED with 3V and with a 3.6Ω and it was drawing 0.25A and it seemed just as bright as the flash AF assist LED. I had them both going at the same time.
Because of the high current draw, I am betting these are IR emitters rather then visible light LEDs. I have seen what a 30mA red LED looks like, and it’s just as bright as these LEDs. So for the extra 10x the power draw, I am betting on them being IR emitters.
I found a similar power IR emitter at Digikey. 400mA, voltage drop of 2.2v. 730nm, which should be a deep red, considering 660nm is the other LEDs I bought, and they’re pretty bright red. Will look for more, but will order this one next time I put an order in. They’re not very cheap at $4.16 a pop.
I don’t really need to buy an LED for this. It’s more for me to figure out roughly what wavelength these AF assist LEDs are in commercial flashes.
Remore trigger port characteristics
I measured the 3 pin connector on the side of the camera where the remote trigger goes. One pin is ground, one pin corresponds to 1/2 shutter press, and one pin corresponds to full shutter press. I don’t know if the full shutter press also engages the 1/2 shutter pin.
What happens on those pins? When the shutter button is not pushed, there’s 3.3v between both pins and ground. When the shutter button is pushed 1/2 or full, the respective pins go to 0V (ground). So if I’m going to use an op-amp (which I am) to pick up and use the the signal, it will have to be an inverting comparator. When there’s a voltage on the op-amp input I need 0V to be seen at the output and when there’s 0V at the op-amp input I need to see full voltage to drive the LED.
Speaking of op-amp, I will need to source an op-amp that can handle 1/2 Amp. The LM358 I have I think can handle 30mA, which is fine for the laser pointer.
I think I will pursue both the laser pointer (line laser) as well as the AF assist emitter from ebay (the 550ex emitter)