Voltage-Surge Protector

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Metal-oxide varistors are inexpensive and usually are readily available (see the sidebar for access information). The amount of protection you need, however, will depend on the type of equipment you have. Television sets are more sensitive than radios, and computers are extremely vulnerable. Therefore, I'm providing you with three types of MOV systems to choose from, according to the degree of protection you need.

GOOD

The simplest protective device requires no construction at all on your part. It consists of a single "MOVed" plug that is inserted into an outlet and has the appliance cord plugged into it. This product, which is solo' by Radio Shack under the name Voltage Spike Protector (part number 61-2790), contains a single MOV device connected across the hot and the neutral power lines. Any transient exceeding 130 volts is readily suppressed by the MOV and is thus prevented from . r, tering the equipment.

Unfortunately, this simple device doe protect against all forms of power surge. 1; the lightning strike is such that voltage spike, of equal proportions are induced in both the hot and neutral wires, the MOV won't sent the change

BETTER

To remedy this shortcoming, I've \e con structed a surge protector that contains three MOV devices. One is wired across the ho and neutral lines, just as is the case with the Voltage Spike Protector. To keep the spike that are common to both lines from creeping into the system, though, I've added two other MOV's-one from each line to the ground wire. With this arrangement, the output t ol: age can never be more than 130 volts iii direction.

You can duplicate this surge protect a matter of minutes, once you've collected t t proper parts and tools. First, you'll need ,; sixoutlet expansion plug. Radio Shack', 61-2622 is one example. Remove the card board back from the outlet by unscrewing the four coarsely threaded rivets on the back w the device.

When you have the back cover off, your, faced with six copper strips that are used to expand a two-outlet socket into a six-outlri one. If you have the misfortune, as I did, o: having the metal strips tumble into hands as you remove the cardboard, don't panic. Simply shove them back into their slots with your thumb.

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