12Vdc to 9,7.5,6 Vdc circuit

This simple converter using a Zener diode and a transistor into a 9V DC 12V DC battery power to the maximum 1A. The circuit is very simple to build, and requires only 3 electronic components, resistors, zener diodes and transistors. The 2N3055 transistors, 1N4738A Zener diode or Zener voltage and the same [...]

Small but powerful multipurpose amplifier
This small amplifier is constructed around the TDA2003 IC, capable of delivering 4Wrms at 4ohms. The TDA 2003 has improved performance with the same pin configuration as the TDA 2002. The additional features of TDA 2002, very low number of external components, ease of assembly, space and cost saving, are [...]

Stops charging when battery is full charged, Portable unit
Charging of the mobile phone, cellphone battery is a big problem while traveling as power supply source is not generally accessible. If you keep your cellphone switched on continuously, its battery will go flat within five to six hours, making the cellphone useless.A fully charged battery becomes [...]