Using arduino as a camera shutter release - optoisolators necessary?

Hi everyone -
I noticed this article on hackaday.com where someone made a intervalometer (triggers shutter once every x seconds and repeat) using not much more than a single Attiny chip. Voltage to power the chip is pulled off the camera's pins, so the chip is running 3.3V (I believe).
Tiny Hardware-based DSLR Intervalometer | Hackaday

I've seen plenty of schematics of people making camera triggers with an arduino, but they use optoisolators (or sometimes transistors) to connect to the camera's remote port. After seeing this article, however, it appears that the chip pulls the trigger pin to ground.

So I ask - If I were to connect the shutter pin on my camera (which is 3.3v i believe) to an output on my Duemilanove, and wrote code to pull it low to trigger - is there any risk to my camera? Just wondering why people use optoisolators in between, and the linked article does not.

Thanks!

First of all a PIC10F222 is not an ATtiny even though the name of the article includes the word 'tiny'.

The author of that article researched his particular camera and determined that the circuit would work with a direct connection. Have you done that with your camera? If you can trigger your camera by connecting it's shutter pin to the case then you may be able to get away without an optoisolator. Whether there would be any risk to your camera or not is another question, but probably not.

Don

The optoisolators offer a little bit extra protection if you mess something up - it stops you breaking an expensive camera! It does work without though.

Dude, spend the fifty cents on the isolator and save yourself the potential cost of replacing the camera. Really. "Necessary", well maybe not.

For example, a parachute is not strictly "Necessary" to jump out of a plane, but if you choose to jump out of a plane without a parachute, the consequences can be.. unpleasant.

but if you choose to jump out of a plane without a parachute, the consequences can be.. unpleasant.

Wouldn't that depend on how far off the ground the plane was?

it appears that the chip pulls the trigger pin to ground.

That is how it works on some cameras but not all. One camera I had use the shutter switch as part of a scanning matrix. In that case what I needed to do was actually short the two sides of the switch. You can’t do this with a transistor but can do it with a FET. So in this case an opto isolated FET rather than opto isolated transistor was needed.

For camera shutter switch optoisolator is waste of PCB space. A transistor operated by 5V max is much safer arrangement than a mechanical switch at the end of 1m cable held in one’s hand. Cable release input (of any half-decent camera) is rated for human model ESD, you can’t possibly generate voltages exceeding this rating with an Arduino.

Cable release input (of any half-decent camera) is rated for human model ESD,

I thought we were talking about hacking into the camera to get at the switch in the shutter release not going through some intended user input. If you do that then there is no ESD protection because the circuit designers are not expecting anyone to do this. 5V is only safe if the cameras supply voltage is this or greater. If it works on say 3V then putting 5V into it could kill it.

The OP was linking to DSLR intervalometer; DSLRs do have cable release connectors.