How to Use Electrolytic Capacitors

Carefully note an electrolytic capacitor's polarity before you use it.

A capacitor is an electronic part that stores electric charge. Capacitors range in size from microscopic to barrel-sized and are made with a variety of different materials. Electrolytic capacitors store charge in a chemical paste called an electrolyte. They have large capacitance values, and are inexpensive and durable. Electronic designers typically use electrolytic capacitors to remove electrical noise from circuits. Since these capacitors are polarized, you must pay attention to the positive and negative leads or risk an explosion.

Things You'll Need

• Electrolytic capacitor assortment
• AA battery
• Multimeter

Instructions

1. Examine an electrolytic capacitor closely. Note that it has its capacitance and voltage values clearly printed on the body of the part. Electrolytic capacitors have capacitance ratings in the range of 10 to 200,000 microfarads. The voltage rating is the maximum voltage to which the capacitor should be subject. Maximum voltages for electrolytics generally range from 20 to 600 volts.

2. Note the polarity marking on the capacitor. One side may be marked with a stripe and a "-" symbol to indicate negative or a "+" to indicate positive. If the capacitor has leads, one may be shorter, indicating the negative lead. While a few electrolytic capacitors are non-polarized, most are polarized. When you install the capacitor to a printed circuit board, match the positive and negative polarity markings on the board to the capacitor's polarity.

3. Hold the AA battery in one hand, positive side up. Touch the positive lead of the capacitor to the top of the battery and, at the same time, touch the negative lead to the battery's bottom. This will put a small, safe charge on the capacitor. Set the AA battery aside.

4. Turn the multimeter on and set its selector switch so the meter reads direct current, or DC, volts. Touch the positive (red) multimeter probe to the capacitor's positive lead and the negative (black) probe to the capacitor's negative lead. Observe that the multimeter briefly shows about 1 to 1.5 volts, and then the voltage drops to zero. For capacitors with values under 100 microfarads, this will happen quickly. For capacitors with values over 10,000 microfarads, it will take several seconds for the voltage to reach zero.

Tips & Warnings

• The AA battery can't put out enough energy to explode a capacitor if you try charging the capacitor backwards. It may shorten the capacitor's life, however.

• If you exceed an electrolytic capacitor's voltage rating, it will burst open and leak a caustic chemical.

• If you install the capacitor with its polarity reversed, it may explode when the circuit is turned on.

References

• Tube Lab: Installing the Capacitors