R8C Measures Negative Voltages

The author had to design a monitor circuit for the so-called Hercules Table (an electrically movable platform) at the University Hospital in Brussels that would watch several operating voltages and could stop the table in case of emergency.

The movement of the platform (up/down) is done with a DC voltage between +8 V and –8 V, where the magnitude of the voltage determines the speed and the polarity determines the direction. There are also a number of fixed voltages that need to be monitored.

An R8C module from Elektor Electronics was selected for the implementation of this project, because it is very easy to connect an LCD module to it and because it has a good A/D converter with 10-bit resolution on board.