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Electronics for dummies - McComb G.

McComb G., Boes E. Electronics for dummies - Wiley publishing, 2005. - 433 p.
ISBN: 0-7645-7660-7
Download (direct link): electronicsfordummies2005.pdf
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2. Connect the disc and neon bulb together by using two alligator test leads, as shown in Figure 14-4.
Place one test lead from the red wire of the disc to one connection of the neon lamp (it doesnít matter which connection). The other test lead goes from the black wire of the disc to the other connection of the neon lamp.
3. Place the disc flat on the table.
4. With the plastic end of a screwdriver, rap very hard on the disc.
Each time you rap the disc, the neon bulb flickers.
Avoid touching the two wires that come from the disc. Although the shock you get isnít dangerous, it definitely wonít feel very good!
Need some ideas for how to use this concoction to impress your family and friends? How about building a light drum?
Follow these steps to build your very own light drum and dazzle your loved ones:
1. String up a whole slew of discs and bulbs in a row.
2. Tape or glue these disc-bulb combos to a plastic base.
3. Get a pair of drumsticks, turn down the lights, and tap on the discs in time with your favorite mood music.
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Chapter 14: Great Projects You Can Build in 30 Minutes or Less 307
Figure 14-4:
Connect the disc and neon lamp, using alligator clips.
Gathering parts for the piezoelectricity circuit
For the circuit that demonstrates piezoelectricity, you need these very few parts:
^ A bare piezo disc (the type that you use in a buzzer, preferably with two wires soldered on)
Neon bulb
^ Two alligator clips
^ Something to whack the disc with, such as a screwdriver or drumsticks (not a baseball bat)
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308 Part V: A Plethora of Projects
Building the Amazing See-in-the-Dark Infrared Detector
Did you ever want to see in the dark like a cat? Now you can, by building this simple infrared detector. The circuit uses just three parts (plus a battery).
You can make the circuit a little fancier by adding an SPST (single-pole singlethrow) toggle switch between the + (positive) side of the battery and the phototransistor to turn the detector on and off; or you can go the simple route and just unplug the battery when you arenít using the detector.
Figure 14-5 shows the schematic for the infrared detector. Be sure to use a phototransistor, and not a photodiode, in this circuit. They look the same on the outside, so check the packaging. Also, be sure to get the proper orientation for both the phototransistor and the LED. If you hook up either one backward, the circuit fails.
Chasing down infrared light
Using the infrared detector, you can test for infrared light from a number of sources. Here are just two ideas to try:
Getting to the bottom of a remote control dilemma: Because remote controls use invisible infrared light, you have a hard time figuring out whatís wrong when they stop working. Does the remote have a problem,
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Figure 14-6:
This miniature camera can see in the dark, thanks to its six infrared-emitting diodes.
Chapter 14: Great Projects You Can Build in 30 Minutes or Less 309
or should you blame your TV or other appliance? To test the remote control, place it up against the infrared phototransistor. Press any button on the remote; if the LED on your project flashes, you know that you have a working remote.
Counter-surveillance: Check to see if somebodyís hidden camera is in your room. These days, covert cameras (such as the one in Figure 14-6) can see in the dark by using a built-in bright infrared light source. You can use the infrared detector circuit to find these sources, even if you canít see them yourself. Turn off the lights and scan the room by holding the detector in your hand and moving it around the room. If the LED brightens, even though you donít see a light source, you may have just found the infrared light coming from a hidden camera!
Although the infrared phototransistor is most sensitive to infrared light, it also responds to visible light. For best results, use the infrared detector in a dimly lit room. Sunlight, and direct light from desk lamps and other sources, can influence the readings.
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310 Part V: A Plethora of Projects_
Detecting parts for the infrared detector
Short and sweet, hereís the list of what you need to build this project:
^ Q1: Infrared phototransistor (our sample circuit uses a RadioShack 276-0145, but almost any phototransistor should work fine)
^ R1: 330-ohm resistor
^ LED: Light-emitting diode (any color)
Cheese It! Itís the Cops!!
Unfortunately, you canít arrest any bad guys when you set off the warbling siren that you build in this project. But it sounds cool, and you can use it as an alarm to notify you if somebodyís getting at your secret stash: Baseball cards, vintage Frank Sinatra records, your signed copy of MisterSpocks Music from Outer Space record, or whatever.
How your Warbler Works
This circuit (see Figure 14-7) uses two 555 timer chips. You rig both chips to act as astable multivibrators; that is, they constantly change their output from low to high to low to high . . . over and over again. The two timers run at different frequencies. The timer chip on the right in the figure produces an audible tone. If you connect a speaker directly to the output of this timer, you hear a steady, medium-pitch sound.
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