Can NPN replace Relay Module

Projects General Guidance
10

Wawa:
Just connecting the pin to the IC might not work if the supply voltages of Arduino and audio chip are different.
The audio chip expects a normally HIGH on the volume pins of 0.7*VCC.
That's 6.3volt minimum on a (typical) 9volt supply of the audio chip.
A NodeMCU (3.3volt) can't deliver that.

So you must use an NPN transistor (with ~3k3 base resistor), with shared grounds.

Or the opto coupler (post#5).
Leo..

i think the opto coupler was the best way :smiley: