Yeah so what’s the minimum circuit to operate phototransistor? (w/ picaxe)
Phototransistor connected
Phototransistor connected between supply and the input, with a pull-down resistor from the input to ground.
Or you can reverse it and have the phototransistor between the input and ground, with a pull-up resistor between the supply and input.
If I remember correctly at least some PICAXEs have weak internal pull-up resistors which you can enable on certain ports, so you could potentially use these instead. The problem with the internal pull-up resistors is that they’re fixed, so you can’t adjust the sensitivity of the circuit.