Electronics projects/ Electronic circuits
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Electronics Projects for Halloween Thrills
With Halloween just ahead I started thinking about how I could use some of the projects in Electronics Projects For Dummies to spice up a Halloween party. Besides the Scary Pumpkins, which are a perfect fit, here are some variations you might try:
Place the circuit for the Couch Petato in Chapter 14 in a Halloween treat paper bag and record Halloween sayings such as ďTrick or treat!Ē on the voice chip. Place the bag of Ďtreatsí on the couch. When people sit down to check out the goodies, theyíll get a surprise.
Add a plastic black cat on top of Sensitive Sam, the line following go-kart, from Chapter 13. Try placing flickering LEDs inside the cat using a 555 timer circuit to create a spooky glow in its eyes. Use electrical tape on the floor to guide Sam with his flickering black cat among your party goers. Remember to reassure them that this black cat wonít cause bad luck by crossing their paths.
Replace the dolphin shapes we used in the light display in Chapter 10 with witches on broomsticks and youíll have witch shaped groups of LEDs flying across your wall.
Use a hand puppet that looks like a bat or ghost instead of the wizard puppet we used in Chapter 7 and program the SpeakJet IC with Halloween cracklings and shrieks that sound off when you press a nose, hand, or wing.
Wireless Scarecrow Project
If you woke up this morning to the sound of deer munching your roses and want a way to keep them out of your garden but donít want to build tall fences that block your view, try this circuit. Designed and recently updated by Charles Wenzel, this gadget detects the vibration of footsteps and sounds a buzzer to scare the deer off. I like Daveís idea of sealing the detector electronics in a jar where it is reasonably protected from the weather. He also added a wireless doorbell transmitter so that you donít have to run wires from the detector to the buzzer.
If youíre not crazy about the amount of noise you need to scare off your local deer you might try an ultrasonic noisemaker. These are used in many commercially available deer repellent gadgets. Check out this circuit which generates ultrasonic noise; you can easily adapt this to work with your wireless scarecrow project.
Turning Gadgets On with a Wave of Your Hand
Would you like to build a gadget that turns on with just a wave of your hand? Dave Johnson has designed the perfect circuit for the task. It compares the signals from two photodiodes using a comparator chip. When you pass your hand over the photodiodes the output of the comparator chip goes high, turning on a transistor which Dave uses to power a buzzer in his circuit.
You could use the same circuit to power a variety of projects. I like the idea of using it for party special effects, where the circuit turns on LED light displays or sounds with a wave of your hand to scare or delight your guests.
In the video Dave provides to demonstrate the circuit the buzzer shuts off after a few seconds. By using flip-flop chips you should be able to modify the circuit so that your gadget stays on until you wave your hand once again.
Circuit for High Speed Photography
Would you like to take photos of split-second events such as the momentary splash when you drop something in a bowl of soup? To take this type of shot you have to leave the camera shutter open and trigger the flash at the split second that the action occurs. One method to trigger the flash at that exact moment is to position an infrared beam and phototransistor so that the object being dropped interrupts the beam. When the infrared beam is interrupted, it triggers the flash to go off a fraction of a second later.
An article by Mathew Swan describes such a circuit, which triggers the flash with an adjustable delay after a light beam is triggered. Mathew has done a very nice job of explaining how the circuit works.
An article by Johannes Eriksson describes his setup for taking photographs of pellets shot from a pellet gun as they strike objects, such as a piece of fruit. This article might give you some ideas about how to set up a completely dark enclosure, required for taking your own high speed photos.
A Better Solar Cell
Spark Fun Electronics is carrying a solar cell that is pretty inexpensive for its output. They measured one in bright sunlight at 9 volts open circuit and 280 volts short circuit, and hereís the part I like, in their office with just sunlight coming through the windows the solar cell generated 110 milliamps. I like the idea of having one of these in my shop window, or mounted outside, to power circuits Iím trying out on my workbench, instead of having to remember to have charged batteries on hand. Check out this solar cell at the Spark Fun web site.
Freeing Up Your Microcontroller
Have you ever found yourself using a microcontroller in a project and wishing you could free up some memory and processing power so that you could add additional sensors? If don't want to change to a more powerful processer such as the Propeller chip, check out an article by Steve Norris. He added small, inexpensive microcontrollers to his circuit to free up processing power in his main microcontroller. The additional microcontrollers were able to control the movement of the four legs of a robot, and to process data from the robot's sensors.
You'll find Steve's article posted on the CrustCrawler Web site. He gives the details of how he used a PIC16F688 microcontroller to control the robot's legs. You may not be able to use the code provided with this article unless you are working with the same robot kits that Steve used, however his use of auxiliary microcontrollers to free up processing power in the primary microcontroller is one you can apply to many projects.
New and Improved Microcontrollers
If youíre interested in how improved microcontrollers and sensors can allow you to build more interesting robots check out the article about the new version of the Lego Mindstorms at Robot Magazines Web site. The new kit includes improved sensors, processor and the ability to control the robot wirelessly from your PDA or cell phone. You can also get more details at the Mindstorm Web site.
If you enjoy building your robots more from scratch, but want to increase the capability of the microcontroller to interface between sensors, motors and computers try the new Propeller microcontroller with eight processors on each chip. The Propeller discussion forum can help you figure out how to build a robot or other projects with this chip.
The Idea behind Guitar Special
If youíre interested in building guitar special effects circuits check out the article titled Tone Clippers by Jack Orman on his Web site titled amzfx (I believe this stands for Analog Music Zone Effects). The term tone clippers refers to the method of using diodes to reduce the amplitude of (or to clip) a signal at various frequencies. For someone new to guitar special effect circuits this article does a great job of explaining the concepts.
The Easy Way to Solder Surface Mount Components; September 1, 2006
If you find an IC that you want to use in a project but itís only available in a surface mount package, hereís an option: Instead of finding another component or learning a technique to solder surface mount packages try the SchmartBoardEZ. Rather than resting package leads on pads you insert the leads into grooves which makes the leads easier to align. The SchmartBoard Web site claims that a ten year old using a soldering iron for the first time can quickly and flawlessly solder a surface mount component using their product. These adapters are pricey, though, so if you have an application that uses a lot and price is an issue, they may not be for you. But for a project that uses only a few, they could be just what you need!
Putting Together a Remote Control Lawn Mower; August 31, 2006
If you like the idea of building a remote control lawn mower check out the instructions for building one on the Popular Science Magazine Web site. The article by Dave Prochnow shows how build the mower he calls the Lawnadillo for about $180. It might take you a while to cut a large lawn using the Lawnadillo since it only cuts a 12Ē wide section on each pass. If you have a few thousand dollars to spare check out the ready made remote control lawn mower at Evatech or the robotic lawn mowers at the Robot Shop.
Building a Variable Air Capacitor; August 28, 2006
When I was writing the radio project for my book I bought a variable air capacitor online. Afterwards I came across this article on eHam.net describing how to build your own. If you like tinkering check out this neat article. It shows each step of the process both in words and photos; with this as a guide it should be easy to build one.
A Birdís Eye View; August 27, 2006
If youíve ever wanted to attach a wireless video camera to your robot, remote control go-kart or in front of your favorite bird watching station check out the miniature wireless video camera at Spark Fun Electronics. Itís inexpensive (about $50) and easy to use.
Long Range Radio Transmitter and Receiver Modules; August 26, 2006
Reynolds Electronics has some new radio frequency transmitter and receiver modules you can use to build remote control gadgets that will work at a distance of about 3000 feet, or just under two thirds of a mile. These are the Linix LR series transmitter module and the Linix LR series receiver module.
Figure 8 of the transmitter module data sheet and figure 12 of the receiver module datasheet show how to wire the modules up to encoder and decoder chips. If youíve built remote controlled gadgets before these datasheets should be enough information, if not look at the tutorials Reynolds Electronics has on their home page for remote control projects for some examples or go through chapter 13 of my book, Electronics Projects For Dummies, to get up to speed.
If someone uses these modules in a project with motors, such as a go-kart or robot, let me know how far the remote control works with the motors on. With other remote control modules I've been able to control something like a horn from a much greater distance when the motors were off. This is because DC motors generate a lot of noise that degrade the performance of the other ICís in the circuit.
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