CHAPTER 7 ■ NINE-VOLT BATTERIESThere are a number of ways to physically connect a 9 V battery to a device. Most consumer products
have specifically designed compartments formed into their cases. With the advent of 3D printing, custom
compartments may be viable options for your robots. At the opposite end of the spectrum, masking tape is
ugly and unreliable.
Rubber bands are okay for securing batteries, though not ideal. I’ve successfully used hook and loop
fasteners, commonly called by their brand name, Velcro. The only problem with hook and loop fasteners
is that one fastener strip needs to be permanently adhered to the battery. A new fastener strip needs to be
attached to each replacement battery thereafter.
Preformed metal clips are available (Jameco #105794 or Mouser #534-080 or #534-095). They have a
screw hole in the middle (see Figure 7-19) that makes it easy to secure against a frame. Use a washer
(a flat, circular disc—see Figure 7-17) on the other side of the robot’s body so that the force of battery
removal doesn’t rip the screw through the body wall.
Figure 7-19. Methods of mounting a 9 V battery: (left to right) rubber band, hook and loop fasteners, clip,
molded part
A word of caution about metal clips: they tend to grab tightly against the battery, causing scrapes on the
battery’s case during installation and removal. The damage is purely superficial, and a little masking tape
around the ends of the clip eliminates the problem.
Molded plastic parts can cradle a battery and provide an electrical connection. If you have room on
your robot for such a part, it’s preferable because the battery is less likely to slip out.
Powering Forward
You’ve now got a power source and you know how to test it. With a little bit of thought given to battery
location, you can find it a spot in your robot. Looking ahead, the 9 V battery will supply power to each of the
upcoming experiments.