How to Read a Diode or Resistor

Diodes ensure that current flows in just one direction. Resistors control how much current flows through a circuit. Both are marked with colored stripes that mean nothing to a person who doesn't understand how to read them. Here's how to decipher the markings.

Difficulty:

Moderately Easy

Instructions

1. Look for the marking - a colored stripe - on the diode or resistor that indicates which way the current flows. The power flows from the end without the stripe to the end with the stripe.

2. Hold the resistor or diode with the stripes to the left.

3. Read the first three stripes to find the capacity (ohms). The first and second stripes are single digits; the third is the number of zeroes that follow the first two numbers.

4. Match the numbers with the colors: black is 0, brown is 1, red is 2, orange is 3, yellow is 4, green is 5, blue is 6, violet is 7, gray is 8, and white is 9.

5. Note that a fourth stripe shows the diode or resistor's accuracy tolerance: Gold indicates +/-5%; silver is +/-10%. If there is no fourth stripe, the tolerance rating is +/-20%. The accuracy tolerance rating means that a certain percentage of power above or below the diode/resistor's rating can go through without affecting the unit.

Tips & Warnings

• An example of the stripe-reading system would be like this: The resistor has, from left to right, a blue, a yellow, a brown, and a silver stripe. The rating is 640 ohms with a tolerance of +/-10%.

• Don't place an under-rated diode or resistor into a circuit. It will blow the component.