Door Phone

Door Phone

by | Jun 26, 2018 | Electronic

LM 386 is just right for a door phone application. It is very useful application in the present urban households. One condenser microphone and a speaker are kept conveniently outside and another set with amplifier are kept inside. With a door phone installed at the...
Improved 3 Transistor Audio Amp

Improved 3 Transistor Audio Amp

by | May 30, 2018 | Electronic

The load resistor for the driver transistor is tied directly to the + supply. This has a disadvantage in that as the output moves positive, the drop across the 470 ohm resistor decreases which reduces the base current to the top NPN transistor. Thus the output cannot...
Simple Adjustable Voltage Source

Simple Adjustable Voltage Source

by | Apr 30, 2018 | Electronic

  A simple but less efficient method of controlling a DC voltage is to use a voltage divider and transistor emitter follower configuration. The figure below illustrates using a 1K pot to set the base voltage of a medium power NPN transistor. The collector of the...
Electronic Lock

Electronic Lock

by | Mar 22, 2018 | Electronic

Here is an electronic code lock, which can be used as a door latch or key for ignition, etc. Operation is fairly tricky and there lies the beauty of the circuit. There are a number of switches, actually nine, which should be operated in a particular and owner –...