APT.GIF Functional Description

All of the circuitry on this drawing is built on the PC Proto Board (Radio Shack part no. 276-1598.

The circuit at the top left is a dual 556 timer configured to detect a missing pulse from the 555 timer on the APT1 circuit. If a pulse is not detected by this circuit, a pulse is sent to the computer reset connector on the computer motherboard.

Several pull-up resistors are located on the top of the drawing.

Two op-amp driver circuits are located at the top right. These drive the Camera/Scope power solid state relay and the dessicator solid state relay.

The circuit an the bottom right is the cloud sensor circuit. The small voltage from the Peltier device (which is sandwiched between two aluminum plates) is amplified by the two bifet op-amps and fed to a 556 timer which functions as a voltage controlled oscillator. Output from the oscillator is buffered by the 7404 and sent to an input bit on the parallel port.