Public Lab Research note

Triggering A495 by button/USB

by warren | March 01, 2012 21:39 01 Mar 21:39 | #881 | #881

I am having trouble connecting the 555 trigger to the A495 camera because the A495's trigger is on a very tiny plastic ribbon, and where it plugs in the leads are miniscule. So I don't think it'll be reasonable for people to open their cameras and attach there.

Instead, I'm exploring how I could connect the 555 timer to the two cameras via the USB port. This will require the CHDK but since they're all the same model, we can have a hard link to the correct firmware to put on your SD card, and a video on how to put your camera in CHDK mode. Now I'm sourcing cheap mini-USB cables and going to test it out.

Useful links:

Totally open to suggestions, just trying to work around an unexpected issue with the trigger not being easy to solder onto.


Too bad about the tiny ribbon, but USB via CHDK is probably a solution that the camera kit Kickstarter backers will deal with gracefully. Because CHDK is written for specific firmware versions, two issues arise. Versions of CHDK are available for three firmware versions of the Powershot A495. I hope all the cameras you have ordered have one of those versions. Also, it will make life much easier for the camera kit backers if both cameras they receive have the same firmware version. If not, the SD cards used in the cameras will not be interchangeable. The camera has to be jumped through some hoops to learn the firmware version. Fingers crossed!

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ug, well these cameras are refurbished, but when we go through them all when modifying them, I'll do my best to mark the firmware version in Sharpie on the outside. Can't things just be simple!?! :-P

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OK, so far both are the "F" model. Taking notes here:

I eventually had to run this command on the files in the SD card to make them executable (on a mac)

cd /Volumes/CANON_DC xattr -d DISKBOOT.BIN PS.FI2

as outlined here:

Now hooking up the USB cables...

CHDK on dual cameras

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OK, awesome - this page lists the voltages needed to trigger the shutter per-camera-model, but does not list the A495:

But 5.5v USB power from an Arduino did work. I'm curious if I can draw 5.5v or something like it from elsewhere on the camera... maybe from the power plug or the A/V port? or from the USB port itself? Hmmm.

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Ok, hacky but cool:

This means we can just ship/order 2-packs of both the battery holder and the batteries themselves, and not muck around with different battery types. There may be a more elegant solution out there using a voltage regulator, but this means fewer parts to order, and seems pretty easy to do.

I tried actually inserting a wire halfway into the A23 battery to use both 12v and 5.5v power at the same time... but that was probably not a good idea and i drained the battery pretty fast. Someone with a formal background in electronics probably would've known better ;-)

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Thats a good idea, but long-term, do we really want a part that requires cutting open batteries to replace? could you step down a 6v battery, or just use 6v? People are going to be using these for a while and that seems like a kind of poor solution for field replacement.

6v batteries are cheap:

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might just want to link to instead of right-clicking, save as ^above for the i did.

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