Simple 433MHz radio-control for a CHDK/SDM PAP camera (or KAP?)

Those looking for a simple means to click the shutter of an SDM- or CHDK-controlled camera might want to take a look at these. Although it talks about interfacing to a basic stamp, all you need at the camera end is a 5v supply and the receiver, I haven't measured the range yet, but it will certainly operate cameras atop my carp pole.

The receiver board has 7 pins:

1. 5v power
2. output voltage (connected to one of the output pins via radio)
3. common ground
4-7. 4 output channels

The 4 buttons on the transmitter connect (on a push) or disconnect (on the next push) pin 2 to one of the 4 output pins. While this does nothing that you can't do hacking a wireless doorbell, the amount of work needed to produce a working control is minimal - it took me just a few minutes of soldering to wire the receiver board to a USB connector (to plug into the camera) and a servo connector (to plug into a 4-cell AAA power supply). The board weighs just 5 grams - less than the two connectors!

Here's the circuit I built:
Simple 433MHz R/C circuit


  • Quick update - I used the control with my 2.4GHz video downlink this morning ans successfully took photos at a distance of 120' (36 metres) - about as distant as I could get in our garden. See here more details.
  • I just took another photo from 280' (85m) away, so this thing is obviously useful for KAP too.
    280 feet away
  • Great to hear that the range is considerable, Dave. I am using Linnar's 433MHz 8-button remote and receiver for CAMremote, and have measured it's range, on the ground, at more than 1000 feet.
  • edited April 2012
    Very interesting find Dave. Thanks for the information about your set up and experiences so far.

    This looks like the same thing for those of us across the pond:


    Would this system handle the current to control a small geared (pan) motor on one of the other output pins?

    Have Fun,
  • edited April 2012
    That definitely is the same pair of devices, Bob.

    Since everything goes through the one chip on the board, I'd be dubious about putting much current through it. The CHDK/SDM method of triggering the shutter by applying 5v across the USB power pins draws virtually no current (the camera just senses the voltage - there's a very high resistance across the pins inside the camera).

    If you want to drive servos or small motors I think you'd have to use a relay mechanism to switch them. I'm thinking of using one of these Pololu servo controllers - you can use some of the channels as analog inputs and write a script to detect when they go from 0v to 5v and thus control servos on other channels.
  • I've seen discussions in the RC plane forums about stacking additional MOSFET chips to increase the current capacities of speed controllers. I wonder if something similar could be done with the output of this device.

    With respect to using a relay, do you think the receiver chip would be able to trigger one of these solid state relays ? Could I use the same 5 volt battery to power both the receiver (and input to the relay) and the output circuit of the relay/motor?

    Have Fun,
  • I'm no expert in these matters Bob, but I think those relays have an opto-isolator inside (ie an LED on the input side is optically coupled to a sensor on the output side) so the current needed to trigger the relay would be very low and not overheat the chip on the receiver board.
  • Hi Dave and others,

    Good to see some more further movement in PAP! I have been using just this transmitter and reciever for some two months now, these are simple component just great for home made PAP electronics.
    My primary goal was not to control the shutter - I let the GoPro do that for partial 'autoPAP' - but to control the tilt angle with a servo.
    This resulted in this setup. image
    For my GoPro PAP-rig

    I had a few problems with the signal. It was needed to attach an antenna to the reciever and to elongate the transmitter antenna to get to 10 meter distance. No idea why that was necessary.
    I found out just very recently a cause. Although the AnyVolt micro is also a great nifty little device (tiny, completely freely adjustable and efficient because of switching technique), it heavily disturbs the signal when its close to the reciever.
    With replacing it with a standard 7805 voltage regulator, no antenna elongation needed any more. So a lesson learned here. Tested it up to 50 meters, indeed far enough for PAP :) Could go further, with antennas the signal is enhanced.

    That Polulo board is very interesting Dave! I will look into that. I used similar looking PPMencoder (that is a device to transform multiple remote control PWM signals to 1 PPM signal). It has an Atmel328P on it. It is simple to change it to a little Arduino device, if you're acquainted with that.

  • Fabian - very interesting, not sure how I missed your experiments, but I'm intrigued to see your antenna changes. Exactly how and where did you attach the long aerial to the receiver?
  • edited April 2012
    No high end solutions here, just a wire attached to the antenna on the transmitter :)
    Effective length is very roughly about half wavelength, wave length of 433mhz is 70cm.
    Sure there are more powerful antennas.

    Other point is that reciever drops out if the servo is powered too. Atmel board keeps running. My provisional solution is: when it reads a signal from the reciever, I just control the servo for some short period. Then servo stops, reciever gets up again, and when the transmitter button is still pressed, the sequence is repeated. It already works good enough for me, but could this be solved in another way, while still using one battery?
  • Dave,

    Can you show us the whole wire diagram?

    What pins on the USB do you use?
  • edited April 2012
    There's nothing much more to it Martin. The USB end is wired to the outer pins (see the diagrams here). Usually (but apparently not always) the two wires in a USB cable to use are Red (connected to the 5v pin) and black (connected to the ground pin).
  • Poor weather for KAP lately has seen me tinkering with a new PAP rig. Basically it uses the same 433MHz radio mentioned above to control tilting as well as the shutter (panning being handled by simply twisting the pole). The two of the four channels provided by the radio are used to handle tilt up and down, one is used to turn the video downlink on and off and the fourth directly controls the camera shutter (via SDM and a USB power pulse). I used a Pololu Micro Maestro 6 channel controller to decode the radio outputs and a Pololu R/C switch to turn video on and off.

    There's a webpage describing the PAP rig here (with circuit diagram and Maestro script) and very short YouTube video of it working here.
  • edited August 2013
    Following my accident in Bologna, I rejigged my KAP rig to use an ultra-cheap 433MHz radio. Its first outing on Sunday didn't go well (at least the R/C bit didn't, but I did produce a decent beach panorama) I discovered the problem yesterday (the key trigger levels were set too high for the somewhat run-down battery and the tilt servo had some stripped gear teeth).

    Anyway you can read more about it here.

    PS I've rejigged the 433MHz PAP rig too - details here
  • Dave: Your facility at creating electronic controls, etc., with easily accessible parts/devices is amazing. I have not tried anything more venturesome than your simple 433 mgz. remote control for triggering a camera shutter (through the USB port via SDM).

    I do have a question: Is there a way using SDM, or some external device, to actually turn the camera on, and then trigger the shutter. I am thinking about situations where I might want to set the camera, wait for the appropriate picture opportunity, turn the camera on and take the picture, then return the camera to an off-state.

    I hope that I am not overlooking some very obvious solution within the SDM menu!

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