Whilst searching for remote camera triggers, I came across this link. Of course, I had to try this out myself. I salvaged some old parts from junk I had laying around and made my own version. It's not the most aesthetically pleasing, but it does the job and it does it well. It features a (DIY) two-modes focus/shutter button and a shutter toggle button for long bulb exposures.
|The remote trigger|
Now on to the technical stuff. My camera can be triggered using a standard 2.5mm stereo jack plug. In the photo above you can see that I used a 3.5mm jack (much more common, I did not have a 2.5mm laying around) and a 3.5mm to 2.5mm adapter (which I already had from hacking around with my TI-84+ calculator). Added benefit: I can use a cheap 3.5mm jack extension chord.
The pin-out for the connector is easy: the tip controls the shutter, the middle sleeve activates the autofocus and the base is ground.
|Another, closer view. Double action switch on the left. Shutter toggle switch on the right.|
The double action works as follows. The top switch is more 'stiff' than the bottom one. When pivoting the top switch, the bottom one clicks first (=focus) and only when pressing further down does the top one click (=shutter). The picture below should make this clear.
|Double switch for focus/shutter. Top: unpressed. Middle: focus (lower switch) active. Bottom: (focus and) shutter active (both switches pressed).|