CHAPTER 9 ■ RESISTORS5% tolerance means that a 100 W resistor could be as low as 95 W or as high as 105 W. That’s plenty
accurate for homemade robots. You can spend a little more money and purchase 1% tolerance metal-film
resistors, but your robot isn’t going to notice the difference. Many of the high-precision resistors have more
than four color bands, which makes it more difficult for a beginner to decipher the value.
Cut It Out
Components often arrive connected together by tape bands (see Figure 9-4). This is because most
components are manufactured in long reels so that they can be fed into robotic part-placement machines.
A reseller purchases a full reel and then cuts off lengths according to your order.
You could try peeling off the tape, but it leaves a sticky residue on the ends of the wires. The residue
can prevent a clean metal-to-metal connection when prototyping. The residue can also gum up sockets
and holes.
Instead, use a wire cutter to cut both ends of the resistor from reel tape. Don’t use scissors because the
cutting edges will become dulled and damaged.
If you absolutely need the full resistor wire length, you can pull the part from the tape and clean the
ends of the resistor thoroughly. Resistors are hardy components; the cleaning won’t harm them at all.
Obtaining a Wire Cutter Tool
A wire cutter is an essential tool (see Figure 9-5). Not only can it cut components free from tape reels, but
also it cuts raw wire, shortens tall component leads in solderless prototype boards, and trims excess material
from circuit boards after soldering.
Figure 9-4. Cutting resistors away from reel tape