CHAPTER 3 ■ SAFETYRooms with just a few two-prong outlets are becoming a thing of the past. Not only did such conditions
become fire hazards as people added on “octopus” adapters, but also, buyers started paying attention
to electrical details when purchasing a home or facility. Thanks to changes in local electrical codes and
ordinances, these issues usually aren’t present in newer homes.
Disconnecting Power
Always physically disconnect power from the robot's circuits before working on it. On larger robots, not
only should the batteries be disconnected, but they also should be literally removed from the robot during
maintenance. This is safer for the builder and it prevents physical damage to power sources. Either way, use
test probes to ensure no power remains.
Use a high-wattage resistor (or a rubber-handled screw driver if you’re desperate) to discharge large
capacitors, as they may continue to store enough power to be harmful even after the primary power source is
removed from the circuit. Large, charged capacitors are one of the reasons that television sets and computer
power supplies can be so dangerous to service.
Never touch a live circuit with both hands—you want to avoid creating a path through your heart. You
should also wear rubber-soled or other insulating-soled shoes. An electrical path from a hand through your
chest and out a foot can be deadly.
Ground paths work because the electricity makes its way through the path of least resistance. If the
electricity finds a low-resistance (think “metal”) route directly to ground, most or all of the electricity is going
to use that path rather than your body.
One last point: human skin is much more conductive when wet. Don’t service your robot or anything
electronic if you or the circuits are moistened. That includes rain or sweaty hands (gross!).
Steering Clear of Dangerous Robots
We’ve got enough problems in this world without people creating deadly robots. Cutting tools, spikes,
hammers, projectiles, and spinning masses all seem like a pretty bad idea on something you’re going to
debug. “Oops! Sorry about your arm. I guess I’ve got those wires backwards.”
Sizing Up Motors
Consider the total size of your robot and the power of the motors needed. Even if intended for good
purposes, moderate-sized motors can produce significant force. Pick up a copy of any industrial-robot trade
magazine and you’ll see they’re full of advertisements for laser beam screens and other safety devices that
immediately disconnect the power to robots when humans (or materials) get too close. Wonder why?
Motors and power components tend to get hot during use. Think about the amount of electrical work
being performed by each piece and the amount of current it is receiving. Every electronic or mechanical part
wastes a portion of the power it receives as heat. The more power something receives, the more total heat it’s
likely to generate.
Lighting Up
A vividly lit area is a joy to work in. Additionally, bright lighting makes it easier to spot mistakes, especially
in circuit boards. If the workpiece is easy to see, it reduces the likelihood of leaning way into the piece or
squinting.