PSoC Polyphonic Piano Cypress Microsystems released a new family of microprocessors some time ago called the PSoC family. These devices are like Lego building blocks for engineers. The development tools are powerful and inexpensive. Here is one o...

White LED Flashlight I took my car to a mechanic recently and while inspecting the seal around the oil pan, he pulled out a small penlight that put out what appeared to be "white" light. When he showed it to me I realized the light was coming fro...

Heartbeat Monitor (HeMon) Here is a circuit from Keith Wilson in Germany for monitoring your heart. The text that follows is his: The heartbeat monitor was originally designed many years ago... One day whilst walking through the town centre in M...

Low Cost Hearing Aids For me, the realization came about seven years ago. My wife, who was sitting to my left, asked me, "Are you going to answer that?" As I turned my head to look at her I began to hear the phone ringing behind me. That was the ...

Build your own Gaussmeter Here's an nifty little project from the Magnet Man, Rick Hoadley. The original can be seen at his home page. Have you ever wanted to find out how strong a magnet really was, or how the strength of the magnetic field vari...

Cranial Electrotherapy Stimulator This design came from RED Free Circuit Designs. According to the information associated with this schematic: "CES is the most popular technique for electrically boosting brain power, and has long been prescribed...

Bicycle Safety Light Here's another design from Red Circuit Designs: Flashing 13 LED unit, 3V supply Also suitable for jogger/walkers Parts: R1 10K 1/4W Resistor R2,R9,R10 100K 1/4W Resistors R3-R8,R11-R16 10R 1/4W Resistors R17 150R 1/4W ...

UV Sensitive Photodetector A UV sensitive photodetector can be realized by using a Siemens BPW34B with a standard transimpedance amplifier. The enclosed schematic shows two different circuits. The circuit on the left is a basic design which can b...

Battery Charger This circuit is an AC-powered current source designed for recharging batteries. It can crank out as much as 1 amp and can be modified to go even higher by choosing different devices for Q1. Since this circuit uses AC line voltages...

Rugged LED Brake Lights OK, here's a simple circuit that was by requested by a reader. Normally, I don't like to run too many LED's in series because if one dies, the whole string goes out. Finding the dead one can be bit problematic as well. So...