Page 76 - Robot Builder's Bonanza

AVOIDING DAMAGE BY STATIC DISCHARGE 45

If your project operates under house current, keep an eye on it for the first several hours
of operation. Note any unusual behavior, including arcing, overheating, or circuit burnouts. If
a circuit breaker trips while your project is on, you can bet that something is amiss with your
wiring.

None of the projects in this book involve constructing circuits that are directly powered by
G household AC current. When AC current is used it’s always through a commercially
manufactured power supply or certified wall transformer. Whenever possible, avoid AC-
powered circuits and use low- cost commercially available power supplies instead.
For obvious reasons, you should always build and operate your projects away from flam-
mable objects, including gasoline, lighter fluid, welding and brazing equipment, and cleaners.
Always keep a fire extinguisher near you, and don’t hesitate to use it if a fire breaks out.
Melting plastic can release highly toxic chemicals and gases. After you put out the fire be
sure to ventilate the area thoroughly. Melted PVC plastic can release hydrogen chloride gas.
Seek medical attention if you’re not feeling well.

Avoiding Damage by Static Discharge

The ancient Egyptians discovered static electricity when they rubbed animal fur against the
smooth surface of amber. When the materials were rubbed together they tended to cling to
one another. While the Egyptians didn’t comprehend this mysterious unseen force, they knew
it existed. Today we fully understand static electricity and know it can cause damage to elec-
tronic components.
As a robo- builder, you must take specific precautions against electrostatic discharge, oth-
erwise known as ESD. Damage from static discharge can be all but eliminated by taking just
a few simple steps to protect you, your tools, and your projects from static buildup.

THE PROBLEM OF ELECTROSTATIC DISCHARGE

Electrostatic discharge involves very high voltages at extremely low currents. Combing your
hair on a dry day can develop tens of thousands of volts of static electricity. But the current
(akin to the force of the electricity) is almost negligible. The low current protects you from
serious injury.
Many electronic components that are manufactured with semiconductor material are not
so forgiving. These include transistors and integrated circuits, especially those that use what’s
known as a metal oxide substrate. These include:

• MOSFET transistors
• CMOS integrated circuits (ICs)
• Just about any microcontroller
• Any module (digital compass, sensor) that contains one or more of the above

Don’t worry if the names of these electronic devices are alien to you. You’ll know a
static- sensitive device when it comes to you in an antistatic plastic pouch or on antistatic foam.
You should keep these devices in their pouch or stuck into their foam until you use them.

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