A two-terminal electronic device, also known as a diode, conducts current in one direction and blocks it in the opposite direction.A transformer converts AC to DC.Since diodes are one-way, it's important to know which end is which.You can usually tell by looking at the markings on the diode, but if they've worn off or aren't present you can use a multimeter.
Step 1: Understand how a diodes works.
A P-type Semiconductor is joined to an N- type Semiconductor.The negative end of the diode is called thecathode.The positive end of the diode is called the anode.If the positive side of a voltage source is connected to the anode, the negative side will not conduct current.The current is blocked if the diode is reversed.
Step 2: There is a schematic symbol that means what it says.
The symbol on the schematic shows how the diode should be installed.An arrow points at a bar with a line continuing out of it.The arrow and vertical bar show the positive and negative sides of the device.The arrow indicates the direction of the flow, which you can think of as the positive side flowing into the negative side.
Step 3: The large band should be seen.
Look for the ring, band, or line printed on the diode if it doesn't have the schematic symbol on it.A large colored band is printed near the negative side of the diodes.The band will go all the way.
Step 4: There is a positive end to an LED.
You can tell which side is positive by looking at the legs.The long leg has a positive anode pin.If the pins have been trimmed, it's a good idea to look at the outside of the LEDs.The negative pin is closest to the edge.
Step 5: The multimeter should be turned to the " Diode" setting.
The symbol for this is the diode schematic symbol.The mode will make it easier to test the multimeter.Without the Diode setting, you can still test the diode.The resistance function is set by the meter.
Step 6: The multimeter needs to be connected to the diodes.
The positive lead should be connected to the one end of the diode.The meter's display should show a reading.If your meter has a Diode mode, you can see the voltage on the meter if it's positive or negative.Nothing will be displayed if it's the wrong way.If the meter doesn't have a Diode mode, you will see very low resistance.If it's the wrong way, you will see a lot of resistance.
Step 7: Test a light.
An LEDs is a light emitting device.The multimeter should be turned to the Diode setting.Put the positive lead on one of the pins.The positive lead is touching the positive pin if the light is on.The leads are touching the opposite pins if it doesn't light up.