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Browsing Archive: March, 2012

intelligent electronic lock

Posted by demysteryboy Inusah on Sunday, March 18, 2012,

This intelligent electronic lock circuit is built using transistors only. To open this electronic lock, one has to press tactile switches S1 through S4 sequentially. For deception you may annotate these switches with different numbers on the control panel/keypad. For example, if you want to use ten switches on the keypad marked ‘0’ through ‘9’, use any four arbitrary numbers out of these for switches S1 through S4, and the remaining six numbers may be annotated on the leftover six s...

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TDA 2030 8W Audio Amplifier

Posted by demysteryboy Inusah on Monday, March 5, 2012,

TDA 2030 audio amplifier can output 20 W but in this schematic we have reduced the power to 8w and we use 10w speakers. The input sensivity is around 200mV and the amplifier is set by the 47k and 1.5k resistors.

TDA2030 amplifier circuit diagram

tda2030 8w audio amplifier circuit diagram


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LM317 audio amplifier

Posted by demysteryboy Inusah on Monday, March 5, 2012,

You probably know that LM317 IC is used as an adjustable voltage regulator, but did you know it can be used as an audio amplifier? This is a class A audio amplifier built with LM317 that delivers a maximum 1W audio power.

Use a good ...

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Cell phone detector circuit diagram

Posted by demysteryboy Inusah on Monday, March 5, 2012,

This cellular phone detector schematic circuit can sense the presence of an activated mobile cell phone from a distance of one and-a-half meters.
If a RF signal is detected the circuit will inform you using a sound alarm (beep sound )...

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Miniature audio amplifier circuit

Posted by demysteryboy Inusah on Monday, March 5, 2012,

This miniature audio amplifier delivers up to 250mW and can be used like a final stage audio amplifier for radio sets. The schematic is very simple: one BC547 transistor controls a balanced power amplifier built with BC337 and BC327. The total amplification is around 15x and is determined by R1, R3 and P1. The input sensitivity is 95mV and the total current consumption is 180mA.

Small audio amplifier circuit diagram

miniature audio amplifier circuit schematic


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