Hack a Canon external Flash for high-speed video marking

June 5, 2012 1:43 PM

How can I hack a Canon external Flash for my high-speed video application?

Hi! I have a few old external flashes for a Canon SLR camera. The one I have before me is a SunPak auto 433AF "Thyristor".

What I was hoping for was a simple shorting of some of the pins to cause the unit to flash... but that didn't get me anywhere.

My application isn't photography per-say. I'm going to be running a test that uses a high-speed video camera (at >1000fps) and need positive indication of certain events happening.

More specifically: I'm going to setup 2 flashes that are controlled by my computer software. The software will send a command to a solenoid valve to open. This signal should trigger the first flash. The solenoid valve will drive a pneumatic remote operated valve to begin to open and the encoder on the shaft will send feedback to the computer. Once the encoder registers >90deg rotation the second flash will occur. These two flashes will help in deciphering the rest of the information in the high speed video.

What kind of signal to what pins of this flash do I need to send to make it work? There is a "test" button that causes the flash. I need to use the pins from the hot shoe. Like...do I send a 5V square "ttl-style" trigger signal to a pin or something like that?

Thanks DIYers for your help :).

posted by nickerbocker to Technology (5 answers total)

Best answer: Worst case, you could open it up and just short the test button, couldn't you? Also, I'm sure you can buy basic non-TTL flashes for dirt cheap on eBay, and on those you can definitely just short the center pin to the side contact to make it flash. I've also ripped the flashes off of disposable film cameras (do they even make those anymore?), and it's easy to fire them by shorting the two wires together. The ones I've played with took standard batteries (AA if I recall correctly, but it's been years).
posted by primethyme at 2:12 PM on June 5, 2012

Best answer: You tried shorting the various pins against the hotshoe rails? Probably the biggest middle-most one is the one to trigger the flash.
posted by aubilenon at 2:24 PM on June 5, 2012

I used the cheap Vivitar flashes the last time I needed "embedded" flash behaviors in photo applications, but the standard flash signal is short the rail to the center pin. On Canon cameras there are 5 center pins, but it should be the big one in the middle to the side rails.

Or, if you've got the cheap version of the corded option there are only two conductors. Short them.
posted by straw at 2:33 PM on June 5, 2012

Response by poster: @aubilenon - Yup, that was it! I did not notice the side "rail" pin :). Thank you very much.
posted by nickerbocker at 3:41 PM on June 5, 2012

Incidentally, when hooking up circuits to camera flashes, you should be aware that some have pretty high voltages that you'll want to take extra care to isolate from more sensitive components (e..g, your computer). It looks like those particular strobes you've got aren't too extreme but 8v is still probably more than you want going into your computer.

It used to be that the shutter mechanically would make an electrical connection between the flash pins, so the voltage didn't really matter at all, so manufacturers just used whatever was convenient with their internal wiring, is why there's such a huge variety.
posted by aubilenon at 4:28 PM on June 5, 2012