In this video, I go over how to trigger a Canon s95 camera through an rc transmitter, without taping a servo on top to push the shutter button. Canon cameras use a firmware hack called CHDK that allows shutter control through the usb port. With a simple switch from Turnigy, we can trigger the camera from the transmitter.

Turnigy switch:

Canon CHDK download and info:

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  • Matt-

    Can you draw up a wiring diagram of how you made your trigger?  This looks like the most promising method, but I'm not entirely sure how you did it.  I don't want to fry any of my equipment so a schematic would be awesome!

  • This seems so simple, but I don't think I'm connecting the wiring right.  Just to clarify:

    1. I connect the servo wire from the Turnigy switch to my intended switch channel on the Rx (in this case CH7).

    2. I'm powering using a 5v Castle BEC

    Here's where I'm confused...

    3. Positive on the USB cable connects to positive from BEC and one of the Turnigy switch outputs

    4. Negative on the USB cable connects to other Turnigy switch wire

    Where does the other negative from the BEC go?  If I connect it to the negative on the USB cable, it just bypasses the switch, correct?

  • Roger, I believe Matt is correct that the camera must be on to use the requested command. 

    However, I've been looking into how to control lens retraction with CHDK.  You could just leave the camera on but have a script to extend and retract the lens.  That way you wouldn't get dust on the lens on take off and landing.

    I want to do the same for my camera that I will put on a plane.  That way the lens can be retracted for landing since the plane doesn't have landing gear.

    Here is all the information I've found so far on the subject:

    Let me know if you give it a try and it works.

  • I don't think you can do that, as it has to be in a state of readiness to recognize the 5v trigger and do the requested command. I could be wrong though. Best thing to do is take a look over at the CHDK website and see if that can be a usb command.

  • Matt,

    Is there a way to turn on a canon camera via chdk? I mean with all the dust circulating around at take off, camera should be off, when in the air, I want to turn it on, then after that use your instruction to take images, when about to land, use chdk to turn off camera. Thanks.

  • Correct. The CHDK is an an alternative to a manual servo for Canon cameras with no infrared sensor or remote trigger input.


    Another great company that sells trigger is

    I use a blipswitch on my Canon 50D DSLR.

  • Distributor

    Great tutorial, but if you dont have a CDHK compatible camera you can use an IR cam shutter controller.

  • Yes.

    5v can come from wherever you can get it. I chose a spare receiver port as I was building the harness, but you can eliminate the need to plug it into a spare channel by using a y-harness and plugging both leads into it, effectively using only one rx channel.

    Or, just solder the positive and negative leads to the switch's servo lead.

    There a number of ways to do it; the way I did it is by no means the only way.


  • Admin

    @ Vishal Tnx

    @ Matt ,  Ok understood. I usually don't have any spare channel on the airframe. Tnx. I assume answer for 1 and 2 is as Vishal says?.

      Early days I had  to use micro servo to switch a micro reed switch for landing lights, it worked great but wish this turnigy was available back then :).

  • Morli.

    to reply to #3. YES.

    I could have easily done this with 1 channel and powered the switch and given the camera 5v from the same pins on one channel. However, since I have spare channels just sitting there, I opted to do it this way.

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