Question
Think of an LED that we plug into a proto board. How do we know which leg of that
LED is the positive (+) leg?
LED is the positive (+) leg?
Answers
GPT-4o mini
An LED (Light Emitting Diode) typically has two legs (or leads), and one of them is the positive (+) leg, also known as the anode, while the other is the negative (−) leg, known as the cathode. To identify the positive leg of an LED, you can look for the following indicators:
1. **Length of the Leads**: Usually, the anode (positive leg) is longer than the cathode (negative leg). If the LED has been previously cut or twisted, or if the leads are of equal length, this method may not be reliable.
2. **Flat Edge**: On the body of the LED, there is often a flat edge on the side of the cathode (negative leg). This can help you confirm which leg is which, even if the leads are of equal length.
3. **Markings on the LED**: Some LEDs might have markings or symbols on the casing. The side with the flat edge or a "−" symbol generally indicates the cathode.
4. **Testing with a Multimeter**: If you're unsure, you can also test the LED using a multimeter set to the diode test mode. Connect the positive probe to one leg and the negative probe to the other. If the LED lights up, the leg connected to the positive probe is the anode.
In summary, the longer leg and flat edge are the most common indicators of the positive leg of an LED.
1. **Length of the Leads**: Usually, the anode (positive leg) is longer than the cathode (negative leg). If the LED has been previously cut or twisted, or if the leads are of equal length, this method may not be reliable.
2. **Flat Edge**: On the body of the LED, there is often a flat edge on the side of the cathode (negative leg). This can help you confirm which leg is which, even if the leads are of equal length.
3. **Markings on the LED**: Some LEDs might have markings or symbols on the casing. The side with the flat edge or a "−" symbol generally indicates the cathode.
4. **Testing with a Multimeter**: If you're unsure, you can also test the LED using a multimeter set to the diode test mode. Connect the positive probe to one leg and the negative probe to the other. If the LED lights up, the leg connected to the positive probe is the anode.
In summary, the longer leg and flat edge are the most common indicators of the positive leg of an LED.