I know this is an old topic but I'm having trouble with this....
I have the parts and the experience but its not quite making sense and it certainly not operating!
My serial interface (ftdi) provides ttl output for RTS#. Ie RTS is operationally low going back high once de-asserted. I can see that using DSLR Shutter and my scope.
The DSLR I am talking to is a Nikon D5100. I measure -4.4v on the focus and -0.2v on the snap tangs of the MCD-1 manual exposure switch, with reference to what I expected to be ground on the middle tang. Remembering this a two-step switch - ground the top tang to assert 'focus' and then push harder to ground the bottom tang to assert 'snap'.
If I assemble it assuming the middle tang is ground, and the Ge diodes (1N60) pointing towards the transistor, grounding the top tang causes a focus action, grounding the diodes does nothing. Since this last action is a test for normal operation, this seems suspect to me that I am getting something wrong.
Does this mean that the middle tang isn't ground ? Is this normal ? The action I am expecting is that closing the first switch pulls the voltage on the 'focus' to ground, further closing the switch pulls the voltage on 'snap' to ground. If that's the case then I have no idea why its showing a negative voltage...
I also have a second MCD unit from the same chinese vendor and its exactly the same.
If the top tang is actually ground and closing the switch pulls first 'focus' then 'snap' to ground, then I need to re-arrange the diodes.
I measured the forward voltage drop on the Ge diodes to be 0.32v
I re-measured the resistor to be 4.7K
Anyone have any ideas?