Electronics_Projects_For_Dummies

130 Part II: Sounding Off!

Black wire

Red wire

Figure 6-13:

Solder wires to the microphone cartridge.

Ground pad

+V pad

5.Twist the free ends of the wires from the microphone cartridge together and feed the microphone wires through the PVC fittings from inside the parabolic dish until the end of the wire reaches the 3⁄8" hole.

If you have trouble pushing the wires around the 90° turn, take a stiff wire with a hook shape in the end (we used some 10 gauge wire; many building supply stores will sell you a few feet of this) and pull the wires through the PVC fittings and pipe.

6.Use a piece of 20 or 22 gauge wire with a hook shape on the end to pull the wires from the microphone cartridge through the 3⁄8" hole.

7.Pull the wires through the 3⁄8" hole, leaving enough wire inside the parabolic dish for the microphone cartridge to reach the 11⁄2" washer with about two inches of slack left over.

8.Cut the wires to allow three inches to extend from the 3⁄8" hole in the pipe and attach each wire to a right-angle phono plug, as shown in Figure 6-14.

You can use either a plug that requires soldering to the wire or one that uses a screw to secure the wire, as we did here.

Chapter 6: Focusing Sound with a Parabolic Microphone 131

Figure 6-14:

Thread wires from the microphone cartridge through the PVC fittings and pipe.

9.From the inside of the dish, put the 3⁄8" inner diameter O-ring over the microphone cartridge and glue the O-ring to the washer, as shown in Figure 6-15.

Figure 6-15:

Microphone

cartridge

in place.

132 Part II: Sounding Off!

Make sure you don’t get glue on the front side of the microphone cartridge, or it could interfere with any sound coming through.

10.Use another cable tie to secure the wires from the microphone to one of the dowels.

Mounting switches and more on the box

It’s time to drill all kinds of holes and pop various components into the box. Follow these steps to do so:

1.Drill holes in the box where you will mount the potentiometer, audio jacks, headphone jack, clamp, and on/off switch, as shown in Figure 6-16.

We put the on/off switch and potentiometer on one side of the box, the headphone jack on the opposite side of the box, and the phono jacks on the bottom of the box.

We kept the headphone jack to one side to keep the output signal from feeding into the input of the circuit (for example, by being near the microphone wires), which could cause feedback.

Screws and nuts

Audio jack securing the clamp

Figure 6-16:

Box with on/off switch, potentiometer, headphone jack, clamp, and audio jacks.

On/Off switch

Potentiometer

Headphone jack

Chapter 6: Focusing Sound with a Parabolic Microphone 133

See Chapter 4 for more information about choosing drill bit sizes for particular components and other advice on 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 on/off switch through the drilled hole and secure with the nut provided.

3.Slip the shaft of the potentiometer through the drilled hole and secure with the nut provided.

4.Slip the knob on the potentiometer shaft and secure with the set screw.

5.Slip the threads of the headphone jack through the drilled hole and secure with the nut provided.

6.Slip the threads of the audio jacks through the drilled holes and secure with the (you guessed it) nuts provided.

7.Slip 8-32 screws through holes in the clamp and the holes you drilled in the box and secure with nuts from the inside of the box.

8.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 6-17.

9.Solder one 8" black wire to the lug on one of the audio jacks and solder one 8" red wire to the lug on the other audio jack, as shown Figure 6-17.

10.Solder 8" wires to each of the three potentiometer lugs, as shown in Figure 6-17.

11.Solder one 8" black wire and one 8" red wire to the lugs of the headphone jack, as shown Figure 6-17.

The red wire should go to the contact that touches the tip of the headphone plug.

Okay, we’ll say it again: Heed all the safety precautions about soldering that we give you in Chapter 2. Don’t ever leave your soldering iron on and unattended. And to avoid damage from flying pieces of solder, wear your safety glasses!

134 Part II: Sounding Off!

Wires to potentiometer lugs

Figure 6-17:

Solder wires to the on/ off switch, phono plugs, potentiometer, and headphone plug.

Black wire to phono jack	Red wire
	to headphone
Red wire to phono jack	jack

Black wire from battery	Black wire	Black wire
pack to on/off switch	to on/off switch	to headphone jack

Putting everything together

After you have a completed breadboard, all the switches in the box, and the microphone and dish assembled, it’s time to put all those elements together.

Follow these steps to finish building your parabolic microphone:

1.Attach Velcro to the breadboard and the box and secure the breadboard in the box.

2.Attach Velcro to the battery pack and the box and secure the battery pack in the box.

Chapter 6: Focusing Sound with a Parabolic Microphone 135

3.Insert the wires from the headphone jack, potentiometer, phono jacks, battery pack, and the on/off switch to the terminal blocks on the breadboard, as shown in Figure 6-18.

Black wire	Red wire	Black wire	Red wire
from headphone	from headphone	from on/off	from
jack	jack	switch	battery pack

Figure 6-18:

Connect the headphone jack, potentiometer, on/off switch, and battery pack to the breadboard.

	Wire from center lug of potentiometer	Red wire	Black wire
	Wire from right lug of potentiometer	from	from
		phono	phono
	Wire from left lug of potentiometer	jack	jack

4.As you insert the wires, cut each of them to the length you need to reach the assigned terminal block and strip the insulation from the end of each wire.

Keep the wires from the headphone jack as far as possible away from the wires from the potentiometer and the wires from the microphone cartridge. Remember how a microphone put too close to a speaker can produce an awful screech? The same screech can assault your ears if these wires get too close together.

136 Part II: Sounding Off!

5.Secure the wires with wire clips where needed.

The way that parts are laid out in this box as well as the distance between some of the components — such as from the phono jacks to the terminal blocks — are both short enough that you won’t need wire clips.

6. Slip the box onto the PVC pipe and tighten the clamp screws.

Don’t tighten them too much; you still need to slide the box into its final position.

7.Put batteries in the battery pack and put the lid on the box, securing it with the screws provided with the box.

8.Slide the box into its final position just below the hole where the phono jacks come out of the PVC pipe. Then insert the phono plugs and headphone plug into the jacks in the box, as shown in Figure 6-19.

Figure 6-19:

The electronics in place.

9.Glue the 1" PVC end cap on the end of the PVC pipe.

You can see the finished product at the beginning of the chapter in Figure 6-1.

Chapter 6: Focusing Sound with a Parabolic Microphone 137

Trying It Out

At this point, the microphone is ready to go, but here are a few tips to help you be kind to your ears — you can get some really loud noises out of this thing.

Before putting on the headphones, flip the switch on and adjust the volume control.

You’ll be able to hear enough to make sure you don’t have the volume so high that it hurts your ears.

Avoid knocking the parabolic dish against anything like a tree trunk or your cat while you have the headphones on. The resultant ringing in

your ears is not a desirable thing.

Avoid having any “friends” shout into the parabolic dish, or anywhere near it, while you have the headphone on.

Time to get this thing in gear. Here goes:

With the headphones on your head, flip the On switch, point the thing at something you want to listen to (such as a neighborhood bird or your best friend), and listen.

If you don’t get the results we got, here are some options to check out:

Check that all the batteries are fresh, tightly inserted in the battery pack, and face the right direction.

Check that no wires or components have come loose.

Compare your breadboard with the photos to make sure all the wires and components are connected correctly.

Taking It Further

After you wander around your neighborhood with your parabolic microphone (and explain to curious passersby what that thing is), you might want to try some variations. Here are our suggestions:

Instead of headphones, hook up a tape recorder to the circuit and record sounds. (Once again, do not record your neighbors because there is probably some kind of law against this — and if there isn’t, there should be.)

138 Part II: Sounding Off!

Get a bigger dish and set it up outside, hooked into speakers you set up in a permanent wildlife listening station either outdoors or in your house. (We say permanent because a dish much bigger than 24 inches needs a wheelbarrow to cart it around.)

If you replace the microphone with a speaker, you could turn this thing on its head and make it a loudspeaker instead of a long-distance microphone. Look up any noise ordinances on the books before trying this one!

Chapter 7

Murmuring Merlin

In This Chapter

Scoping out the schematic

Running down the parts list

Breadboarding the wizard’s circuit

Programming a sound synthesizer chip

Placing the board in the puppet

Getting sounds from Merlin

Apicture can be worth a thousand words, but sometimes a word — or sound — is just what’s needed. In this project, you work with a sound

synthesizer chip, an amplifier, and a speaker. With this setup, you can produce almost any sound you can imagine.

You can place a sound chip in just about anything and use switches to activate sounds. For this project, we chose a hand puppet (ours happens to be a wizard because we’re into fantasy fiction); a hollow puppet lets you easily insert the project breadboard and switches. However, you can use anything you like for your talking pal.

As you work through this project, you discover how to work with programmable sound synthesizer chips as well as a bit about how amplification works.

The Big Picture: Project Overview

When you complete this project, you’ll have a talking hand puppet. You can program the synthesizer chip inside the puppet with any messages you like. For example, we programmed ours to say, “The check’s in the mail,” “You can’t have more money,” and “Where’s the darn chapter?!” — and then we gave it to our editor.