PCF8591 - Voltage Input and Output

This is an interesting module, which as shown, comes with a selection of try it and see inputs, as well as being able to be used for general analogue I/O. This one comes with an LDR, a thermistor and a variable resistor soldered to the board, which can be selected or deselected via jumpers, so from the off can be used as a thermometer, light meter and a test source.

Removing the jumpers means that the inputs all come from the pins so that it can be used to measure voltages. This is a limited range so an input voltage divider will be needed in most use cases.

Typical use cases may be water meters, light meters, temperature sensors or current measurements as well as voltage.

An interesting feature of this module is that it can also output a controlled voltage. This is a low power source but where voltage control is needed then this is an option. Typically this will be voltage controlled light sources or audio controls, but as the voltage output can be used with switches, the module allows a single on/off feature to be combined with the analogue voltage input.

This is a bidirectional module, so can be used to publish measured voltages or set an output voltage based on a MQTT subscription.