Electronics_Projects_For_Dummies

310 Part IV: Good Vibrations

SPST normally open (NO) momentary push button switch (S4)

Holtek HT12E encoder (IC1)

1 megohm resistor (R1)

TWS-434 RF transmitter module

We bought this at Reynolds Electronics (www.rentron.com); Hobby

Engineering (www.hobbyengineering.com) carries a similar module.

400-contact breadboard

One 4 AA battery pack with snap connector

Five 2-pin terminal blocks

Plastic box

We use Radio Shack part #270-1806.

An assortment of different lengths of prestripped short 22 AWG wire

Figure 13-5:

Key components of your

transmitter.

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Running down receiver and container parts

The circuit that takes transmitted signals and explains to Sam what’s expected of him involves the following parts, several of which are shown in Figure 13-6:

Holtek HT12D decoder (IC1)

L293D H-bridge (IC3)

LM555N-1 timer (IC2)

Five 2N3904 transistors (Q1–Q5)

6 volt buzzer

RWS-434 RF receiver module

We bought this at Reynolds Electronics; Hobby Engineering carries a similar module.

Four 1 amp or greater solid state relays, DPDT (double-pole, doublethrow) or SPDT (single-pole, double-throw)

We used the Shinmei RSB-5-S DPDT that we found at Jameco (www. jameco.com). A SPDT would also work, but we used the DPDT because it allows for more flexibility for which side of the relay we could run wires to. Make sure that the relay you buy has a pinout pattern that fits a breadboard; many of them do not.

Two DC gear motors GM2 each with a 25⁄8" wheel or equivalent

We use these because the suppliers (Hobby Engineering (www.hobby engineering.com) or Solarbotics Ltd. (www.solarbotics.com) carry wheels made to fit them.

Two metal brackets used as motor mounts

We found 3" x 5⁄8" mending braces made by National Manufacturing Company at our local hardware store. These worked great.

One 11⁄2" inch swiveling castor

Six 0.1 microfarad ceramic capacitors (C1, C3, C6, C7, C9, C11)

Six 10 microfarad electrolytic capacitors (C2, C4, C5, C8, C10, C12)

51 kohm resistor (R1)

Three 10 kohm resistors (R3, R5, R7)

Two 150 ohm resistors (R4, R6)

330 ohm resistor (R2)

Two 830-contact breadboards

Two Fairchild QRB1134 sensors

312 Part IV: Good Vibrations

Three 4 AA battery packs with snap connectors

Ten 2-pin terminal blocks

Four 8-32 11⁄2" panhead screws

Four 8-32 nuts

Four 6-32 1⁄2" panhead screws

Four 6-32 nuts

Four 4-40 3⁄4" panhead screws

Four 4-40 nuts

Two wooden boxes

•2" wide x 5" tall x 11⁄4" deep

•51⁄2" wide x 81⁄2" long x 21⁄2" deep

We found one at a local craft supply store that was just the right size to hold the electronics for this project and a smaller wooden box to glue on the front of the bigger box to mount the sensors.

An assortment of different lengths of prestripped, short 22 AWG wire

Figure 13-6:

Important

pieces of

the Sam

project.

Chapter 13: Sensitive Sam Walks the Line 313

Taking Things Step by Step

The steps involved in making Sensitive Sam sensitive are

1.Making the transmitter circuit and fitting it into your remote control box

2.Making the receiver circuit that goes into Sam

3.Putting together the chassis that contains the receiver circuit (Sam’s body)

Making the transmitter circuit and remote control box

The transmitter circuit fits into a remote control box and allows you to turn Sam on and off, speed him up or slow him down, and sound his horn. Here’s what’s involved in making this circuit:

1.Place HT12E (IC1) and five terminal blocks on the breadboard, as shown in Figure 13-7.

The five terminal blocks shows in this figure will be used to connect two wires each to various components in the circuit. The wires from these terminal blocks will go to the battery pack, the on/off switch, the transmit switch, and the three toggle switches.

Figure 13-7:

Place the IC and terminal blocks on the

breadboard.

314 Part IV: Good Vibrations

2. Solder an antenna wire to Pin 4 of the transmitter module, as shown in Figure 13-8.

See the earlier “Building Alert: Construction Issues” section of this chapter for some tips on how to do this.

Figure 13-8:

Transmitter and voltage regulator (VR1) pinouts.

3.Insert the voltage regulator (VR1), a 1 megohm resistor (R1), and the transmitter module on the breadboard, as shown in Figure 13-9.

Chapter 13: Sensitive Sam Walks the Line 315

Voltage regulator

Figure 13-9:

Insert a resistor, voltage regulator, and the transmitter on the breadboard.

4.Insert wires to connect the IC, voltage regulator, transmitter, and the terminal blocks to the ground bus. Then insert a wire between the two ground buses to connect them, as shown in Figure 13-10.

Sixteen shorter wires connect components to ground bus; the long wire on the right connects the two ground buses.

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6.Insert wires to connect the IC, voltage regulator, transmitter, and terminal blocks, as shown in Figure 13-12.

S1 TB to Pin 10 of IC1

Battery TB to VR1 input pin Pin 17 of IC1 to transmitter data input pin

Figure 13-12:

Hook up the ICs, terminal blocks (TBs), transmitter, and voltage regulator.

S4 TB to Pin 14 of IC1 S2 TB to Pin 12 of IC1

S3 TB to Pin 13 of IC1

The next step is to drill all kinds of holes into which you can pop various components to create the remote control box. Follow these steps to do so:

1.Drill holes in the box where you will mount the on/off switch, speed switch, horn switch, start/stop switch, transmit switch, and antenna, as shown in Figures 13-13 and 13-14.

You can rearrange the switches. Just be careful not to put a switch where it will be in the way of the battery pack when you mount it inside the box.

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See Chapter 4 for more information about choosing drill bit sizes for particular components. In that chapter, we also offer advice about how to customize a box for your projects. Make sure you use safety glasses when drilling, and clamp the box to your worktable!

2.Slip the shaft of the switches through the drilled holes and secure with the nuts provided.

3.Solder the black wire from the battery pack to one lug of the on/off switch and solder an 8" black wire to the remaining lug of the on/off switch, as shown in Figure 13-15.

4.Solder an 8" wire to each of the two lugs on the pushbutton transmit switch, as shown in Figure 13-15.

Figure 13-15:

Wires soldered to the on/off switch and transmit switch.

5.Solder 6" wires to each of the two lugs on each of the three switches mounted on the cover, as shown in Figure 13-16.

If you have 22 gauge stranded wire, consider using it for connecting the switches mounted on the cover. Stranded wire is more flexible, which makes getting the cover on the box easier. As we discuss in Chapter 4, solder the end of the stranded wire to gather all those loose strands.