I need to make a device that's totally sealed, but is powered by, and communicates with, the outside world.
For communications, I'm thinking along the lines of embedding IR LEDs and phototransistors in the boards, and talking that way.
Alignment in the z direction should be easy -- that can be achieved by two flat plates that touch. Alignment in the x and y directions would be super-simple to get down to 1mm of error, and 0.2mm should be doable if necessary.
I'm thinking of just aiming LEDs at photo-transistors in the opposite device, and using on-off keying. But I'm not sure what sort of data rates I can achieve, and at what current consumption. I'd like to aim for115200 baud, using no more than 0.5 mA for both transmit and receive. Less current consumption would be absolutely wonderful.
So, my questions are:
- Am I nuts? Is this too much to ask for from available parts?
- Should I do something fancier than driving an LED with a resistor and a logic output? Do LEDs persist in glowing after the current goes to zero, and can you turn them off faster by actively sucking current out by the judicious application of some negative voltage?
- Should I do something fancier than hanging a resistor off the collector of the photo-transistor and looking at the output?