Also, there are a few pre-built modules used, namely a DC-DC converter and a Dual H-Bridge Motor Driver circuit.
If you're not going to drive a motor, then you can skip the Motor Driver section and if you use a 5v battery pack you can skip the DC-DC converter section. Jump straight down to the Camera Shutter Circuit section.
We'll start with the Dual H-Bridge Motor driver.
Next, we'll look at how we power the Raspberry Pi. Now we don't want to have a second battery just for the Pi, so we can use a DC-DC converter to give us 5v. A typical DC-DC converter is shown in the next image.
Finally, we look at the circuit to drive the camera shutter. It's simpy a couple of NPN transistors, one for the focus and one for the shutter release.
The shutter release port in a DSLR will typically have 3 pins. One GND, one for focus, and one for the shutter. There's just like GPIO inputs, in that they will have a 3.3v voltage across them, and are activated by shorting them together. So, grounding the shutter pin will activate the shutter in the camera.
Some cameras need the focus pin actived before the shutter pin. Other cameras will trigger the camera with just the shutter pin shorted. On Canon DLSR's just the shutter pin is needed so one transistor and one resistor will suffice. Here's a diagram of the circuit. If you need to activate the focus pin on the camera, do a second one of these for the focus pin.
A couple of acrylic cases are ideal. You can leave the top off one of the cases for the PiTFT, as it's conveniently the same size as the Raspberry Pi. All the other circuitry can be put in another case below, and hidden away underneath the Raspberry Pi. You can also add suitable connectors for everything.
- DC jack socket for the 12V input from the battery pack
- DC jack socket for the 12V output to the motor
- Stereo 3.5mm headphone socket for shutter release cable to DLSR
- Power switch to switch everything off and on