LED Resistors – Does Resistor Position Matter in LED Circuit?


I was reading the MAKE AVR programming. One of the chapters suggests to solder resistor to the cathode side of an LED.

But in our uni labs it's said to connect the resistor "before" the LED; that is connect the resistor to the anode.

Does the positioning of the resistor matter at all? In case of accidentally burning out the LED? If so, how?

Best Answer

No, it does not matter. There are several cases:

  • The LED works: in this case the resistor will limit the current flow, and does not matter if it is before or after, since it is connected serial.
  • The LED does not work:
    • Electricity flows through the LED: it would go through the resistor anyway, either if it is before or after the LED.
    • Electricity does not flow through the LED: current will not flow anyway through the resistor because the circuit is not closed.