Easy transistor circuit won't work

Other Hardware General Electronics
5

dc42:
It looks to me that you are missing at least 2 things:

  1. A resistor between the Arduino output and the base of the TIP121, without this you are likely to burn out the Arduino pin; and

  2. A ground wire between the emitter of the TIP121 and the Arduino, unless the ground is connected via the power supply.

How do you know your IR LEDs are not working?

  1. Which resistor would be good?
  2. The ground wire of the emitter goes to the GND of the power supply, is that a problem?
  3. They give a red glow, and I have an IR sensitive camera.