How to Read a Diode

Diodes are common devices with many different functions.

A diode is a piece of electrical equipment that ensures an electric current flows only in one direction. The diode allows the current to pass in its forward direction, but blocks any current flowing in the opposite direction, often referred to as the reverse direction. Diodes can also be used to electronically tune electrical devices such as TV and radios, generate radio signals and produce light. Reading a diode takes some practice, but is relatively easy.

Instructions

1. Read which direction the current flows in. This is indicated by a colored stripe. The current flows from the side with no stripe towards the striped side.

2. Turn the diode so the striped side is to the left.

3. Read the first three stripes. These will be colours. The first two stripes are the capacity in ohms, and the last stripe is the number of zeros at the end of the number.

4. Analyze the colours against the diode chart. Black -- 0, brown -- 1, red -- 2, orange -- 3, yellow -- 4, green -- 5, blue -- 6, violet -- 7, gray -- 8 or white -- 9. For example, if you had the colors orange yellow red, your reading would be 3400.

Tips & Warnings

• There may be a fourth stripe which shows the diode's accuracy. This will be gold to demonstrate +/-5% or silver for +/-10%. If there is no colour, the accuracy rating is +/-20%.

References

• "How to Test Almost Anything Electronic"; Delton T. Horn; 1993.
• "Electronic and Electrical Servicing: Consumer and Commercial Electronic"; Ian Sinclair and John Dunton; 2007.