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[...]... diode, and the other a light-emitting diode (the two arrows represent light leaving the device) The diode symbol shows an arrow (anode) pointing at a line (cathode), and this will indicate which way current flows (from the anode to the cathode, or in the direction of the arrow) On many small diodes, there will be a stripe painted around the case to indicate which end is the cathode, 10 and on LEDs, there... on the underside of the perforated board using some hookup wire and a soldering iron Then, it was tested with a fresh battery and the lights off If you find that the unit will not start when the lights are out, test first to ensure that there is sound output by removing the CDS cell completely, which will cause the unit to start dripping When you reinstall the CDS, the unit will stay quiet until there... to the oscillator The higher the frequency rating of the speaker, the farther the high-pitched sound will travel, which is why a two- or three-inch diameter tweeter is optimal for this project The small speakers shown in Figure 2-6 are perfect for this project, and I included a piezo buzzer as described in the last project, as it can also be used with a simple modification of the oscillator circuit The. .. Attacks! Scare Them Silly! Project 48—Spring-Loaded Launch Pad Project 49—Trap Door Cage Project 50—Light-activated Trigger Project 51—Fluffy’s Body 221 51 High-Tech Practical Jokes for the Evil Genius This page intentionally left blank Chapter 1 Introduction If you have never cracked the case on an electronic device, or have never wielded the unlimited power of the almighty soldering iron, then fear not—I... interconnect the circuit using small bits of wire with the insulation removed at each end To make changes, simply move the wiring around Figure 1-17 shows the solderless breadboard I used to develop all the circuits in this book and many hundreds of other projects Also shown in Figure 1-17 (inset) is the relationship between the connected strips and the holes in the board The Atmel processor plugged into the. .. nicely into the cabinet I chose to help disguise the evil device Now, let’s get on to the design of the electronics that make this unit work Figure 2-7 shows the schematic of the beeping thing, and you may recognize some similarities between this schematic and the last one, as they are based on similar parts and principals In the schematic, the 555 is set up so that its output will turn on the two transistor... formed by the pair of NPN transistors Just like most 555 timer circuits, the timing cycle is controlled by the two resistors on pins 6, 7 and 8, and by the capacitor connected to pins 1 and 2 If you play around with the values of the two resistors, you can control the duty cycle of the timing pulses in order to alter both the off time and on time of the cycle to create more or less beep each time the. .. resistors Resistors Resistors, like the ones shown in Figure 1-5, are the most basic of the semiconductors you will be using, and they do exactly what their name implies—they resist the flow of current by exchanging some current for heat, which is dissipated through the body of the device On a large circuit board, you could find hundreds of resistors populating the board, and even on tiny circuit boards... you want it to, then remove the variable resistor to measure the impedance (resistance) across the leads in order to determine the best value of fixed resistor to install On a variable resistor, there are usually three leads: the outer two connect to the fixed carbon resistor inside the can, which gives the variable resistor its value, and a center pin that connects to a wiper, allowing the selection... on both the shape and material used to make the enclosure Project 2—Evasive Beeping Thing Figure 2-4 The dripper circuit assembled Where to hide such a device? Well, there are so many possibilities I found that an empty deodorant case worked perfectly as shown in Figure 2-4 There was enough room for the battery, the piezo element, and the circuit board Owing to the extreme sensitivity of the CDS cell . Experiments for the Evil Genius 123 Robotics Experiments for the Evil Genius PC Mods for the Evil Genius Radio and Receiver Projects for the Evil Genius Solar. Projects for the Evil Genius 25 Home Automation Projects for the Evil Genius BRAD GRAHAM KATHY MCGOWAN 51 High-Tech Practical Jokes for the Evil Genius New