If your circuit is behaving weirdly, switching on when you touch a wire or move your hand over the circuit you almost certainly have a floating input. You can solve this problem with a pull-up resistor. Many AVRs have built-in pull-up resistors that you can turn on using code.

In Sketch:

pinMode(2, INPUT_PULLUP);

In BascomAVR:

Config Portb.1 = Input Set Portb.1

There’s a great article at SparkFun about Pull-up Resistors.

  • Arghblarg
    1·
    1 year ago

    I’d also add: always have a cap between your AVR’s VCC and GND. Unless your power supply is incredibly clean, it’s good to have.

    • MapleEngineerOPMEnglish
      2·
      1 year ago

      Very, very good point. I always put a 0.1uF cap between Vss and Vdd on my chips as close to the chip as I can get it.

      As I understand it many chip manufacturers specify what cap or caps you’re supposed to use for decoupling. I saw a video where the guy said that the manufacturer of the chip that he was talking about suggested a small ceramic like I use plus an electrolytic. I’ve never done that. I should probably look at the datasheets more often.

      Thanks for the comment!