CHAPTER 3 ■ SAFETY
Don’t purchase or use items containing mercury. Mercuric-oxide, silver-oxide, and even zinc-air
batteries contain mercury. As long as people continue to buy products with mercury, they’ll continue to be
manufactured. If you use a mercury switch in your robot and the switch shatters, spewing mercury all over
your robot, how are you going to clean it up? The robot is covered in toxin.
Don’t throw away items containing mercury, but instead take them to a local hazardous waste
collection site for proper disposal or recycling. Most types of consumer batteries are accepted at local
hardware stores (or Target or Wal-Mart) for disposal and recycling at no charge. Seriously, a few minutes of
your time here can make a significant impact on the environment.
Cadmium
Cadmium is also a hazardous element. Don’t buy nickel cadmium (NiCd, NiCad) batteries, even at a surplus
sale. Nickel-metal hydride (NiMH) batteries are a superior replacement, in several ways.
Take items containing cadmium to a local hazardous waste collection site for proper disposal. Again,
many local retail stores accept batteries for disposal at no charge.
Purchasing Safer Parts Labeled RoHS
The European Union has a regulatory initiative called RoHS (Restriction of Hazardous Substances). This
initiative is also being adopted in various forms by states and countries throughout the world. The purpose
is to reduce the usage of certain harmful elements and compounds. Manufacturers that comply with the
requirements can label their product RoHS.
This initiative is being adopted broadly across the electronics industry. In particular, you’ll notice
seemingly identical components with part numbers that differ by only a single digit or letter. The difference
is usually that the newer part has either been certified or modified to be RoHS-compliant.
Figure 3-5. Three glass tilt switches with noxious liquid mercury