Solar Cell Sensor Instrument Circuit, 1993

Four 0-450 mV solar cells are monitored by a laptop via its 25-pin (DB-25) parallel printer port. Signals from the solar cells are multiplexed into a single channel 8-bit ADC, and the 8-bit outputs are sent to the laptop 4-bits at a time, all under laptop control via additional lines on the DB-25 connector.