Electronics_Projects_For_Dummies

Chapter 13: Sensitive Sam Walks the Line 341

1. Place black electrician’s tape on a reflective floor (hardwood or linoleum, for example).

You don’t have to create a straight line; you can use several pieces to design a circular or oval track.

2.Place Sam on the track with the sensors on either side of the tape.

3.Put batteries in Sam and the remote control flip the on/off switches on both to On.

4.Flip the start/stop switch to start and press the transmit button on the remote control to get Sam moving.

5.Flip either the speed or horn switch on the remote control and then press the transmit button to activate either effect.

6.To stop Sam, flip the start/stop switch to stop and press the transmit button.

If nothing happens, here are a few things to check out:

All the batteries are fresh, are tight in the battery pack, and face the right direction.

See whether any wires or parts have come loose.

Compare your circuit with the photos in this chapter to make sure you got all the connections right.

If Sam gets going but doesn’t follow the track as you expect, you can adjust the sensors by loosening the screws and sliding the sensors up or down.

If Sam stalls, try these steps:

1.Put the start/stop switch in the start position.

2.Push the transmit button once more.

Taking It Further

We’re sure you can see why this neat little guy is Earl’s favorite project. You can create huge tracks and have him follow around the room. He confuses recalcitrant cats (refer to Figure 13-1), and you can put notes in his cart and send them to someone else on the other side of the room.

Chapter 14

Couch Pet-ato

In This Chapter

Looking over the schematic

Laying down the parts list

Breadboarding the Couch Pet-ato circuit

Installing the breadboard and components in the case

Sounding off!

You arrive home from a fast-paced game of racquetball, eager to grab a bag of chips and a cold can of soda, and then just veg out on your

couch. As you walk in the front door, though, what do you find but your 30pound cat, Reggie, spread out on the couch. Adding insult to injury, he’s purring loudly — and shedding to beat the band.

Want to be saved from this annoying scenario forever after? That’s what this chapter is all about: using a vibration/tilt switch sensor in a gadget that will sound off if Reggie (or Fluffy or Rover) so much as lays his paws on your furniture.

Chapter 14: Couch Pet-ato 345

Couch

Pet-ato

circuit.

Here’s the rundown of the schematic elements:

The sensor — one of the key components of this circuit — is used to detect Fluffy jumping on the couch. This vibration/tilt switch sensor detects motion or vibrations when the switch is mounted with the body of the sensor horizontal to the bottom of the box. When the sensor detects motion, it closes a switch, just like how a toggle switch works.

IC1 is the other key component of this circuit. This is a chip that you can use to record a sound or voice message and play it back. We connected the sensor between Pin 24 of IC1 and ground. When the sensor detects motion and its contacts close, Pin 24 is connected to ground, which triggers the playback.

S1 is a normally open (NO) pushbutton switch that when depressed, connects Pin 27 of IC1 to ground. This causes the IC to record sounds or words that you speak into the microphone. Recording stops when you release the S1 pushbutton.

Chapter 14: Couch Pet-ato 347

Signal Systems 3004 tilt/motion sensor

Many vibration (also called tilt or motion) sensors are available; we used cost and pin type as our criteria. We found this sensor at Jameco (www. jameco.com), and Mouser (www.mouser.com) carries a similar lowcost sensor. We chose this one because it doesn’t use a surface-mount package, which is harder to work with.

16 ohm, 0.2 watt speaker

Electret microphone part #EM-99

We found this one at Jameco. You can use other electret microphones; see Chapter 3 for the criteria to help you choose one. If you use another model of microphone, you might have to adjust R3 to get the supply voltage to the correct level.

Winbond Electronics ISD1110 voice record/playback chip (IC1)

0.01 microfarad capacitor (C1)

0.1 microfarad capacitor (C3)

4.7 microfarad electrolytic capacitor (C2)

Four 5⁄8" 6-32 screws

Four 6-32 nuts

Three wire clips

5.1 kohm resistor (R1)

470 kohm resistor (R2)

2.2 kohm resistor (R3)

NO (normally open) momentary pushbutton switch (S1)

Breadboard (830 contacts)

SPST toggle switch (S2)

Four pack of AA batteries with snap connector

Four 2-pin terminal blocks

Enclosure

We use a wooden box 8" x 51⁄4" x 31⁄4", with latches and clasp.

Velcro

An assortment of different lengths of prestripped short 22 AWG wire

348 Part IV: Good Vibrations

Figure 14-3:

Key components.

Taking Things Step by Step

Creating your Couch Pet-ato involves wiring the circuit; installing the speaker, microphone, battery, switches, and circuit board in the box; and then connecting the whole shebang.

Start at the beginning — by wiring the circuit. Follow these steps to build your Couch Pet-ato circuit (but be sure not to let Rover know what you’re up to).

1.Place the voice chip IC and four terminal blocks on the breadboard, as shown in Figure 14-4.

The four terminal blocks shown in this figure will be used to connect two wires each to various components in the circuit. The wires from these four terminal blocks go to the battery pack, on/off switch, record switch, and microphone, respectively.

Chapter 14: Couch Pet-ato 349

Figure 14-4:

Place the voice chip IC and four terminal blocks on the

breadboard.

2.Insert wires to connect each component and terminal to the ground bus and insert a wire between the two ground buses to connect them, as shown in Figure 14-5.

In this figure, six shorter wires connect components to the ground bus (marked with a – on this breadboard); the long wire on the left connects the two ground buses.

Figure 14-5:

Connect components to the ground bus.