- 1). Connect the resistor to the positive terminal of the LED. LEDs should not be connected directly to a power supply since the large current will burn it out. In order to calculate the value of the resistor, use the following equation:
R = (Vs - VL ) / I
Vs is the power supply voltage, VL is the LED voltage and I is the LED current. For example, if the power supply is set to 9V, the LED voltage is 2V and the LED current is 10mA, then the resistor value would be:
R = (9 - 2) / 0.01 = 7 / 0.01 = 700 Ohms - 2). Connect the remaining terminal of the resistor to the positive terminal on the power supply.
- 3). Connect the negative terminal of the LED to the negative terminal of the power supply in order to complete the circuit. Switch on the power supply and set the voltage to 9V. The LED should light up.