I'm building a PIC controller for an antenna rotator. The rotator will be mounted about 100 feet from the ham shack, and the I want to control/power it over a five-wire control cable. Three of the wires are used to control a split winding, capacitor start/run 24VAC motor. Of the other two wires, one is a DC ground return, and the other was used to connect to a wire-wound rehostat used as a not-very accurate heading indicator.
The rehostat is the weak point in this design, it has gone bad, and a replacement is too expensive. I have replaced the rehostat with a disk on the motor shaft and a opto-interrupter. One 220Ω resistor from +5V through the LED emitter, and a 22K pull-up on the collector of the photo-transistor gives me a clean 5V pulse once per disk rotation, suitable for a digital input to the PIC.
Here is my problem: the connection above requires three wires, +5V, GND, and the PULSE out. I would like to reduce this to two wires; some method of modulating the photo-transistor current onto the LED emitter current, and then separating the two currents at the other end of the 100ft run. The circuit could be powered either from 5V (the PIC supply), or from an unregulated 15Vdc supply. The goal is to deliver a clean pulse to the PIC pin.
Anybody have any ideas?
The rehostat is the weak point in this design, it has gone bad, and a replacement is too expensive. I have replaced the rehostat with a disk on the motor shaft and a opto-interrupter. One 220Ω resistor from +5V through the LED emitter, and a 22K pull-up on the collector of the photo-transistor gives me a clean 5V pulse once per disk rotation, suitable for a digital input to the PIC.
Here is my problem: the connection above requires three wires, +5V, GND, and the PULSE out. I would like to reduce this to two wires; some method of modulating the photo-transistor current onto the LED emitter current, and then separating the two currents at the other end of the 100ft run. The circuit could be powered either from 5V (the PIC supply), or from an unregulated 15Vdc supply. The goal is to deliver a clean pulse to the PIC pin.
Anybody have any ideas?