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]

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]

Balanced microphone preamp

The following circuit is a balanced microphone preamp. Feature : Simple circuitry, inexpensive, 60dB amplification, 12V supply voltage. Component : Resistor, transformer, potentiometer, ne5532, rectifier, 7812, 7912, fuse, capacitor, 7805, zener diode. [nomad.ee]

12 V to 100V DC/AC inverter

 The following circuit is a 12V to 100V DC/AC inverter using SN7400. Feature : input voltage is 12 VDC, output voltage is 100VAC, the oscillator’s frequency is 60Hz. Component : SN7400 nand gate, resistor, 1S1588 diode, capacitor, 2SD880 transistor, 78L05 regulator IC, 2N3055 transistor, Transformer.[piclist.com]