Today we are going, how to check diodes and leds. Diode is a two terminal electronic component. That conducts current in one direction one output is the cathode and the other one is the anode. You may check the diode using a multimeter.

Diodes and leds
Cathode and anode

Switch the meter to diode test mode. Now take the diode attach the negative probe to the cathode and the positive to the anode. The display shows a voltage drop on the diode for 185 millivolts. We change the probes and the meter shows nothing. It means no current is running through a diode that’s how it should be the diode is okay.

There are diodes of different design ones like this and another type in glass housing called Zener diodes. Testing procedure is the same negative to the cathode and positive to the anode. The cathode is marked with a colour stripe on some diodes. In case the diode is broken it will.

let the current flow in both ways or not let it pass at all. Now let’s learn how to test light emitting diodes there are different types of leds typical dip leds and smd leds. Using light bulbs and led strips you test them the same way as simple diodes.

Let’s take an led for example the green one.It also has a cathode and an anode. We attach the probes the only difference is that when you see a voltage drop on the screen. The led lights up because the 3 volts generated by the multimeter is enough. However it may be not enough for lighting up some smd leds have a look.

How to use digital multimeter

We take the pcb from a light bulb one of the diodes is working.We checked it before we touch it with probes nothing happens.We are repeated with probes switched same result in such cases a more powerful power source is needed for testing.We take a 9 volt battery now we touch the led outputs and it lights up.

Some seemed leds may have several crystals in one housing and they need more voltage to light though for lighting.Most of them those three walls the multimeter provides should be enough.

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