52 Part I — Hardware Hacks
−
To GPS
+
+ |
− + |
− |
FIGURE 3-11: Diagram of the completed setup
This kind of battery pack gives you great flexibility. You can either keep it in your pocket and use it only when needed or you can run your GPS from the battery pack and remove the pack once it is spent and switch to the internal batteries.
A Different Kind of Battery Pack
You can also use different kinds of batteries, and you’re not limited to 1.5-volt batteries. A good battery to choose is the CR123A lithium cell (nonrechargeable) commonly used in photography (see Figure 3-12).
FIGURE 3-12: CR123A lithium cell
Chapter 3 — Power Hacks 53
With two of these, a little wiring to put them in parallel, a connector, and a Kodak Advantix film canister (see Figure 3-13), you can create a small, simple, high-capacity battery pack.
FIGURE 3-13: Simple starting material
Here’s how you build this pack:
1.Take a Kodak Advantix film canister and make a small pinhole near the bottom on the side; as shown in Figure 3-14.
2.Put a small amount of modeling clay into the bottom of the film canister. You will need to experiment with the amount that you use here. This will be used to push the batteries up against the terminals. Figure 3-15 shows a cutaway of what you are aiming for here.
54 Part I — Hardware Hacks
FIGURE 3-14: Carefully make a hole in the bottom
Cutaway of film pot
Film pot
Wire |
Plasticine |
terminal |
|
FIGURE 3-15: Cutaway showing plasticine in the bottom of the film pot
Chapter 3 — Power Hacks 55
3.Take a paper clip and bend it as shown in Figure 3-16. This will act as the terminal connector for the battery’s negative terminals.
FIGURE 3-16: Terminal made from a paper clip
4.Now for the positive terminals at the top. Take the lid of the film pot and make two notches through the rim of it, cutting it at the narrow ends of the lid (at the points of the ovals in the lid). These notches will accommodate the terminal at the top of the pack.
5.Take a second bit of plasticine and another paper clip and repeat what you did at the bottom of the film canister, as shown in Figure 3-17. This figure also shows the notches cut in the lid.
6.Now you need a GPS connector properly wired to a suitable wire. Then, take the wire from the negative pin of the connector and solder that to the paper clip at the bottom of the film canister, as shown in Figure 3-18, and then solder the wire from the positive pin to the paper clip at the top. You will need to make a small hole in the lid to enable the wire through. Add a small drop of hot glue to make it waterproof.
56 Part I — Hardware Hacks
FIGURE 3-17: The top of the completed film pot. Note the notches at either end of the lid accommodating the wire for the terminals.
FIGURE 3-18: Hot glue for waterproofing