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Building Alert: Construction Issues ...........................................................

Sam is sensitive, and so are some of the issues you’ll encounter when build-

ing him. For example, the motor lugs used in this project are made of thin

metal and will break off if you put too much stress on them. By using

stranded wire, rather than solid wire, you can minimize the stress on the

lugs. Throughout the construction instructions that follow, we indicate when

to use stranded wire.

Another construction issue to be aware of is the antenna. You solder antenna

wire to one lead on both the transmitter and receiver modules. A 12" 20 gauge

wire makes a dandy antenna; unlike 22 gauge wire, 20 gauge wire is stiff

enough to stay upright. The only complication is in soldering the wire to the

leads on the modules, so here are a few tips:

Keep the soldering time to a few seconds to avoid damaging some of the

solder joints in the module.

Leave^1 ⁄ 4 " of lead below the solder joint to allow you to insert the adja-

cent leads fully into the breadboard.

Soldering the 20 gauge solid wire directly to the lead is acceptable; how-

ever, soldering a few inches of stranded wire to the end of the antenna,

covering that joint with heat shrink tubing, and soldering the stranded

wire to the module lead prevents the leads from being twisted while you

work with them.

Twisting can put too much stress on the lead and break it off, which is

more likely to happen if you solder solid wire directly to the lead.

Perusing the Parts List ................................................................................

We broke down the parts shopping list into two... um... parts: a list for the

transmitter circuit parts and a list for the receiver circuit and container parts.

Tallying up transmitter bits and pieces...........................................

The circuit that sends signals to Sam telling him what to do involves the fol-

lowing parts, several of which are shown in Figure 13-5:

LM7805 5 volt voltage regulator (VR1)

Four SPST toggle switches (S1, S2, S3, S4)

Chapter 13: Sensitive Sam Walks the Line 309