Analog Threshold Relay

This is part of my readout electronics system.

This is one of the oldest modules I built that I haven’t desoldered so far. It is an analog threshold relay with voltage reference and amplification.

There is a 10V reference voltage feeding into the 10-turn potentiometer on the front panel, this selects the threshold voltage. A lever switch selects whether the input signal is amplified by x10 or just passed through to the comparator. The comparator (LM358) itself is a window comparator where another lever switch selects whether to take the trigger signal from the under- or over voltage outputs. The selected output then triggers a relay. The LED on the front panel is dual-color (R-G), where red indicates that the unit has triggered and green indicates that the unit is powered and ready.

There is a manual test button that instantaneously triggers the relay, this can be used to test any connected circuits for proper function, without having to take the unit out of service.

PCB View Front Panel