Electronic Dice Circuit

An electronic dice is a classic first project for those getting interested in electronics. A timer, counter and a few LEDs makes a circuit that can also add a new twist to some old boring board games. When the switch is pressed, a 555 timer in astable mode pulses a BCD counter which lights up a series of LEDs wired to mimic a dice. Two AND gates are used to reset the count back to one whenever the BCD output is seven. Thus, the circuit is not truly random but the natural bounce present in a pushbutton and the normal human ability to operate much slower then the oscillator make the output of the circuit seem random.

IR Remote Switch Circuit

This circuit lets you control any line powered electrical device (a lamp, television, fan, etc.) using any infra-red remote control. Almost everyone these days has a pile of old IR remotes left over from appliances they have long ago disposed of them. With this circuit, you can put them back into use. The circuit looks for any modulated IR source and uses it to control a TRIAC, which then switches any appliance connected to it's socket. For example, you can use it to control the room lighting in your home theater setup using any of the remotes you already have. The circuit is powered using a simple transformerless power supply from the line itself, making it compact and easily built into a light switch, wall box, power bar or even the appliance you wish to control. 

40W Fluorescent Lamp Inverter

This 40W fluorescent lamp inverter allows you to run 40W fluorescent tubes from any 12V source capable of delivering 3A. This is basically a larger version of the 12VDC Fluorescent Lamp Driver and can be used to light regular or blacklight tubes.

3 Channel Spectrum Analyzer

This 3 channel 15 LED spectrum analyzer is the perfect addition to any audio amp project. It produces fantastic displays on three LED bars that can be individually adjusted for any particular frequency range. The circuit will take line level output from most any audio source, and operates on 12V DC. This means that it can even be run in a car.

Mono To Stereo Synthesizer

This circuit attempts to liven up mono sound sources by simulating a stereo signal. It does this by shifting certain frequencies between left and right to fool the ear. It can often produce a passable mock stereo sound to bring some depth to otherwise flat recordings. Of course, there is no way to produce real stereo sound from a purely mono source unless the synthesizer had a way to tell which direction the original sound came from, but an illusion is generally enough for all but the hard core audiophile.

Wireless Auto Tachometer

Anyone performing their own automobile tune-ups knows how important it is to know your engines speed. With this tachometer, you can measure your engines speed without any connections or annoying timing lights.
Schematic:

AC Motor Speed Controller

This AC motor speed controller can handle most universal type (brushed) AC motors and other loads up to about 250W. It works in much the same was a light dimmer circuit; by chopping part of the AC waveform off to effectively control voltage. Because of this functionality, the circuit will work for a wide variety of loads including incandescent light bulbs, heating elements, brushed AC motors and some transformers. The circuit tries to maintain a constant motor speed regardless of load so it is also ideal for power tools. Note that the circuit can only control brushed AC motors. Inductive motors require a variable frequency control.