I designed this module as a real time clock with external temperature measurement module. The unit provides a set of DPDT relay contacts, one 120v 5A AC solid state switch, RS232 port and a full ASCII

8 segment display. The microprocessor is based on the 8051 architecture. I used the Atmel AT89S8253 in the design shown which can be programmed via ISP using the Microelektronica 8051Prog2 pod.

I designed the PCB artwork to accept earlier versions of the 8051 with the ability to place an external watchdog timer, (DS1232). The input supply voltage range is 7 to 12vdc or 6 to 9vac.

View Schematic Diagram

  The above photo shows the complete prototype PCB. This unit is designed ot operate from -40 to +85 deg C.