The next step is control. We need to be able to fire all the cameras at the same time and control each one individually. Luckily, the Olympus SP-510 UZ was chosen in part because it has an optional external shutter release cable that allows you to trigger the shutter, hold it open and close it all through the USB port. But to make this cable work in the matrix you need to:
1. hack the cable
2. extend the length of the cableTo Hack the Cable:
Open the the plastic casing on the remote cable release
with a small phillips screwdriver. You will see three spring steel metal "fingers" stacked above one another with a small offset between each one. These fingers are conductive. Each finger has a single conductor connected to it. When you presh the button a plastic feature applies a pre-load on the spring fingers, which in turn bend to touch one another in series; First the top finger touches the middle, then the middle and top fingers both make a connection with the lowest finger. This action corresponds to three states of action in the camera: (1)Open circuit -- when the fingers are not touching, the camera is asleep (or awake if you recently took a photo, but the camera is inactive); (2) Half-trigger -- when you partially depress the button, the top finger touches the middle one and triggers the half-release mode; (this allows you to trigger auto-focus or wake the cameras from sleep without taking a photo) and (3) when you fully depress the switch you open the shutter and begin taking a flick. When you release the button the shutter closes and the camera is ready for another photo.
so this means:- The top conductor is the half-trigger control wire.
- the middle conductor is power (a multimeter confirms).
- The bottom conductor is full-trigger control wire (i.e. take a photo dog!).
Now label those conductors and cut cut em. You can toss the plastic housing right in the landfill. Don't cut the small usb connector on the opposite end of the cable. We need that.
For our purposes we can connect the half-trigger and the full-trigger release leads together.
We will control the camera by "pulling up" the half/full trigger wire(s) to the power bus (which is 5VDC provided by the USB port of the camera).You can still use the half-trigger function by quickly closing and opening the circuit from the control box. There is a ~1 second lag between flipping a switch on the control box and the actual triggering of the camera.
(see drawing below for more detail on the inside of the cable release housing.)Extend the Cable:
I used a 24 AWG twisted pair of stranded conductors in a single insulated cable for each camera. To solder this together I used:
- a Weller soldering iron
- wire stripper
- wire cutter
- liquid flux
- shrink tube
- electrical tape
- wire ties
These parts all commonly available in a hardware store or a radio shack (see materials list in step 1 for links).
This next part of a pain in the ass (cuz the insulation on most consumer equipment is cheap and not heat resistant and the conductor are typically small):
1. strip the half trigger and full trigger leads
2. twist the the half trigger and full trigger conductors together, flux and solder them.
3. solder the half/full trigger bundle to the one of the twisted conductors.
4. strip, tin and solder the power lead to the other twisted conductor in the cable
5. Use shrink tube and tape to add strain release on both wires. Use wire ties to create a "service loop" for strain release.
6. cut back the cable insulation and expose the two conductors on the opposite side of the cable. You can strip the wires as they will need to fit into a screw-down terminals.
7. Repeat for N number of cameras. This gets real old real fast.
ON the other end of the cable you will have two leads: camera control (thats the half/full trigger bundle we soldered together) and camera power. I soldered all the camera power leads together in a big solder ball, with a single wire jumper i could plug into the box, the i covered it all with electrical tape. Bad form right, but i had some people breathing over my shoulder. The camera control leads will plug into the control box and the screw-down terminals. Label these cables with tape and a sharpie now and save yourself a little grief.