Home Improvement

How do you know which side of a LED is positive and negative?

If the LED has two leads with leads that are equal in length, you can look at the metal plate inside the LED. The smaller plate indicates the positive (anode) lead; the larger plate belongs to the negative (cathode) lead.

Which side of an LED goes to positive?


For an LED to work it needs to be connected to a voltage source with the correct side. The voltage supply side of the diode is the positive (+) side, this is called the anode. The negative side is called the cathode.

Which end of the LED is the positive end?


The longer leg is the positive side of the LED, called the “anode,” and the shorter leg is the negative side, called the “cathode.”

Does the side of a LED matter?

1) Polarity Matters

And when there’s no current-flow, there’s no light. Luckily, this also means that you can’t break an LED by plugging it in backwards. Rather, it just won’t work. The positive side of the LED is called the “anode” and is marked by having a longer “lead,” or leg.

Which pin is positive on an LED?


The positive pin is the ANODE (+) and the negative pin is the CATHODE (-). It is very important that LEDs are connected to a circuit in the right direction. The current flow can flow only from the ANODE (+) terminal to the CATHODE (-) terminal. If the LED is connected in the wrong direction it will not illuminate.

How can you tell cathode from LED?

LED Polarity

The cathode is marked on the rim of the LED body with a flat area shown in the diagram. Another way to tell which lead is the anode and which is the cathode is to look at the two plates at the end of the leads inside the body of the LED. The bigger plate will be the cathode.

What are two ways to determine the negative leg of an LED?

You can try to find the longer leg, which should indicate the positive, anode pin. Or, if someone’s trimmed the legs, try finding the flat edge on the LED’s outer casing. The pin nearest the flat edge will be the negative, cathode pin.

Which way do LEDs go?

The positive side of the LED is called the “anode” and is marked by having a longer “lead,” or leg. The other, negative side of the LED is called the “cathode.” Current flows from the anode to the cathode and never the opposite direction.