Tip 2. Radio Controlled (RC) shutter release for Sony alpha camera

New cameras have different solutions for remote control of the camera. Some, like Sony cameras, can be controlled by infrared light or by wireless network. These solutions have disadvantages concerning range and battery capacity. Some solutions only allow jpg-file format. I was thinking a better solution would be to control the shutter by radio control. Those who have been enjoying the model airplane hobby will know this technology and may have a transmitter and a receiver in house. I have found ideas for this construction on the web, so thanks to those who have contributed.

I used a cheap servo for the project. Other stuff that is needed are three resistors, one at 130 ohms, the two others at 2.2 kohms. Then an optocoupler (optoisolator) of a simple type. I used the 4N35. You also need a LED of ordinary type. To mount the components I used a Veroboard piece, but prototype board or a wooden plate with small copper nails can do the same job. The current to drive the circuit comes from the receiver which must be connected to a 5 V battery. The servo comes with leads and a connector for the receiver which can be used as it is.

The servo must be taken apart. The only component that is needed in the servo is the electronic circuit board (PCB). The motor and the gears are removed. The potentiometer which is sitting on the motor axis is also removed. Instead of the pot meter two resistors at 2.2 kohms are used. They are soldered between the middle lead and each of the other two leads (see diagram Fig. 1). Then the two leads that were connected to the motor are delivering the signal for the camera shutter. On one of the leads is soldered a resistor (130 ohms) and an LED. Be sure to get the LED mounted the right way as to polarity. The LED has a dual function. It gives a light signal when the signal from the servo electronic circuit board is coming. Then it also also allows only one way polarity, rejecting current in the opposite direction. The LED is then connected to the optoisolator port 1. The other lead of the original motor leads is connected to port 2 on the optoisolator. The optoisolator is functioning as a relay for the camera shutter. The optoisolator is fast and short-circuits the shutter contacts on the camera remote. The shutter contact  has 3.2 V on the Sony A700. Since there is no need for autofocus on the camera (focus should be set manually), the white lead and the red lead  can be connected together. On the A700, the upper contact on the camera remote is for the screen in the remote cable, the middle contact is for the red wire and and the lower contact is for the white wire on the remote. Connecting red and white wakes up the camera and starts the autofocus if this is activated on the camera. Connection between all three wires releases the shutter. The remote cable wiring is identical on the old Minolta alpha cameras and the Sony a700.

This construction works well on my Sony a700 camera. I connect the original servo leads to channel 5 on my Futaba receiver. This is a channel for landing gear and has no proportional control, only on-off. The switch is very fast and the LED gives a red blink as the shutter releases when I switch this channel quickly on-off on the transmitter.

It will be an advantage to have some soldering practice and some beginner’s knowledge about electronics before you start on the project. I take no responsibility for the possible failure of your camera whatsoever, and this project is not recommended if you have no previous practice in electronics.

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Fig. 1. Circuit diagram for the RC remote on-off switch for camera shutter,

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Fig. 2. Servo dismanteled.

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Fig. 3. Receiver, battery, and on-off switch with remote cable to camera. Note that the wires to the cable remote do not have the correct color code.

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Fig. 4. Close view of the RC on-off switch.

Note added on 18. september 2016: The wires to the camera remote contact have been given colors that match those in the a700 remote cable release.