Bicycle back Safety Light

This is a circuit of bicycle back safety light. Feature : 13 LEDs flashing, 3V supply voltage, Simple circuitry, low voltage, high efficiency, battery powered. Component : Resistor, capacitor, LED, switch, battery, 7555 timer IC. [redcircuits.com]

Four-Hour Timer

The following schematic diagram is four hour timer circuit. Feature : easy to build, 3 hours 53 minutes total time,9V supply voltage. Component : 555 timer IC, Resistor, capacitor, switch, transformer, LED, CD4040B, Relay, BC547 transistor, 1N418 diode, variable resistor. [wiredworld.tripod.com]

Isolated Full Duplex RS232C Interface Circuit

This is a Isolated Full Duplex RS232C Interface circuit. This circuit is used to protect PC from direct connection to hazardous voltages. Feature : isolate TxD and RxD lines from the PC serial port , baud rate of 19.2k baud, 5V supply. Component : capacitor, 1N4148 diode, LED, DB9, terminal block resistor, 6N137, CNY17-3, 74HC14. [chaokhun.kmitl.ac.th]

NiCad Discharger for Rx & Tx Packs

This is a NiCad discharger circuit for Rx and Tx Packs. Feature : Simple circuitry, for NiCad battery, Tx battery 8 cell pack,Rx battery 4 cell pack. Component : LM3900 op amp, BD681, LED, resistorm capacitor,7805 voltage regulator, push button, BC548 transistor, Buzzer. [sentex.ca]

Motorcycle Battery Charger

The following schematic diagram is a motorcycle battery charger. Feature : 115 or 220V Ac supply voltage, current of 3A, full indicator, simple circuitry, 14.1 volt output. Component : LM350, Transformer, bridge rectifier, capacitor, resistor, potentiometer, 1N4148 diode, BC558 transistor, 1N4001 diode, LED, LM1458. [sentex.ca]

Light Pollution Meter

This is a light pollution meter circuit. Feature : control range of about 2 to 30 microamps, Simple circuitry, easy to build, battery powered, 9V supply voltage. Component : LED, NPN transistor, Digital multimeter, Resistor, potentiometer, toggle switch, battery. [avery.home.mindspring.com]

Water-level Alert

The following circuit is a water level alert. Feature: Simple circuitry, low voltage, 1.5V supply voltage, portable unit, battery powered, low current consumption. Component : Resistor, capacitor, LED, 1N5819 diode, 7555 timer IC, piezo sounder, Battery. (redcircuits.com)