Twinning Pentax ZX-M's
By Vlad Rex
The first image shows the complete system. Cameras are sitting on battery
packs, so everything looks a bit bigger then it should, but I save a lot on
lithium battery costs. Note, that only three cables connect both cameras through
available remote release electrical connectors. Camera on the left side is the
master. Once the release button is pressed there, both cameras fire
simultaneously (of course each camera must be turned on first, unfortunately
that must be done for each camera separately). Connection cable has three wires:
ground, preset and release signals.
The
second image shows a close-up of a connector on master camera. The plug is
"double-ended". This way the remote release Pentax cable can be still
used, when needed (as shown, but it is never needed in free-hand photography).
On the lens you can see a piece of a ribbon cable socket. Two pieces of it were
used to create the plug that connects to Pentax remote release outlet.
The third image has all cables disconnected. To make a thinner part of the
plug, three openings were removed, leaving only one row that fits to camera
connector. Visible black shrink wrap hides diodes isolating the cameras
electrically in one direction. Original Pentax release cable can be connected to
the socked via angled header (normally used electronic boards as terminators for
jumpers or
connectors for ribbon cables).
Now, how do you select a master camera. Each camera has it's own power
converter transforming battery voltage (that goes down with use) to a stable
source for it's electronics. Most likely one camera will not have the same
internal voltages when compared to another camera. The difference will be in a
fraction of 1 Volt. Measure voltages in both cameras. Connect a digital
voltmeter to ground and release (or pre-set) pins. (make sure it's not an old
analog type using coils - they may induce some high voltage and damage the
camera). Use as a master the camera that has a higher reading. This is done to
prevent a parasitic battery drainage when both cameras are connected with our
cable.
Cable connecting two cameras should have diodes placed as shown below:
