Another power question

Hi

For my project I am stacking 2xIOPlus and a GPIO expander HAT on top of a Pi4.

The solution is going to read >20 switches being grounded, and trigger >20 lamps (with their own 6v driver circuit) by toggling HIGH/LOW (with or without a resistor - unclear what voltage/milliamps the lamp trigger needs at present, but it isn't much).

The buttons that trigger all the activity are connected to GPIO pins.

Firstly do I *need* an additional 5v PSU ?

And if I do, could I beg you to recommend one as the choice from Farnell/RS is bewildering to a non-electronics programmer !

Hi

You should not need an additional power supply with two IO Pi Plus boards.

The 20 inputs will draw very little power, if you use the internal 100K pull-up resistors the total current for 20 inputs would be 1mA.

For the outputs, the maximum current the MCP23017 IO chip can supply is 25mA per channel or 125mA in total so with 20 outputs you will be using less than 250mA which is well within what the Raspberry Pi can supply on its GPIO header.

Many thanks !