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7. Use 22 gauge single strand wire, preferably already pre-cut and trimmed for use with a solderless breadboard, to finish making the connections.
Folks commonly refer to these wires as jumpers; most of the circuits you build will have at least one or two. Use the sample breadboard in Figure 14-2 as a guide to making these connections.
8. Before applying power, double-check your work. Verify all the proper connections by cross-checking your wiring against the schematic.
9. Finally, attach a 9-volt battery to the V+ and ground rows of the breadboard.
The V+ row is on the top, and the ground row is on the bottom. Itís easier to use a 9 volt battery clip, which you can get at RadioShack and other electronics stores. Itís a good idea to solder 22-guage solid hookup wire to the ends of the leads from the clip; this makes it easier to insert the wires into the solderless breadboard. Remember: the red lead from the battery clip is V+; the black lead is ground.
When you apply power to the circuit, the LED should flash. Rotate the R1 knob to change the speed of the flashing. If your circuit doesnít work, disconnect the 9-volt battery, and check the connections again.
Here are some common mistakes you should look for:
^ You inserted the 555 IC backwards. This can damage the chip, so if this happens, you might want to try another 555.
^ You inserted the LED backwards. Pull it out and reverse the leads.
^ You didnít press the connection wires and component leads into the breadboard sockets firmly enough. Be sure that each wire fits snugly into the breadboard, so there are no loose connections.
^ The component values are wrong. Double-check, just in case!
^ The battery died. Try a new one.
^ You wired the circuit wrong. Have a friend take a look. Fresh eyes can catch mistakes that you might not notice.
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304 Part V: A Plethora of Projects
An LED flasher with parts mounted on a solderless board.
Running down the LED flasher parts
Here are the parts that you need to build the LED flasher circuit:
^ IC1: LM555 Timer IC
R1: 1 megohm potentiometer R2: 47 Kohm resistor R3: 330-ohm resistor
Its good electronics practice to build a circuit thatís new to you on a breadboard first, as you often need to tweak a circuit to get it working just the way you want it to. Once you have it working to your satisfaction on a breadboard, then you can make the circuit permanent if you like. Just take your time, and remember to double- and even triple-check your work. Donít worry ó youíll be a pro in no time, and building fairly complex circuits on your solderless breadboard.
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Chapter 14: Great Projects You Can Build in 30 Minutes or Less 305
C1: 1 |iF tantalum (polarized) capacitor ^ C2: 0.1-|iF disc (non polarized) capacitor ^ LED: Light-emitting diode (any color)
Putting the Squeeze on with Piezoelectricity
Not all electronic circuits require batteries, resistors, capacitors, transistors, or any of the other usual components that you find in an electronic circuit. This project generates its own electricity and you end up with a light drum consisting of a neon light that glows when you tap on a piezo disc. It serves as a great demonstration of something called piezoelectrics.
Piezo ó what?
The term piezo comes from a Greek word meaning to press or squeeze. Many years ago, folks with too much time on their hands found that you can generate electricity when you press certain kinds of crystals really hard. Lo and behold, these same crystals change shape ó though only slightly ó when you apply electricity to them. It turns out that this find was an important discovery because we use piezoelectricity in tons of everyday gadgets, such as quartz watches, alarm buzzers, barbecue grill starters, and scads of other devices.
Experimenting with piezoelectricity
A simple and fun way to experiment with piezoelectricity is to get a bare piezo disc. You can find these discs at most electronics stores and also online. You can get them very cheaply; usually a dollar or less apiece.
Get a disc with the two wires already soldered onto it. Some discs only have one wire; these discs work just fine, too. You can clip a wire to the edge of the discís metal for the ground connection.
Figure 14-3 shows a demonstrator circuit with one disc and one neon bulb. (Try RadioShack or other electronics stores to get the neon bulb.) Neon bulbs are special in that they donít light up unless you feed them at least 90 volts. Thatís a lot of juice! But the piezo disc easily generates this much voltage.
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306 Part V: A Plethora of Projects
Try this simple circuit to demonstrate the properties of piezoelectricity.
PIEZO DISC POWERING A NEON BULB
To build the circuit in Figure 14-3, follow these steps:
1. Place the disc on an insulated surface.
A wooden or plastic table surface works fine, but donít use a surface made of metal.