Tag Archives: hobby projects

Water level alarm circuit

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Description. Here is a simple water level alarm circuit using 555 timer that will produce an audible alarm when the water level reaches  a preset level.The circuit can be powered of a  3V battery and is very handy to use. The circuit is based on an astable multivibrator wired around… Read more »

Transistor intercom circuit.

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Description. Here is a simple but effective intercom circuit that is based fully on transistors.The circuit is based on a three stage RC coupled amplifier. When the pushbutton S2 is pressed, the amplifier circuit wired around T1 & T2 becomes an astable multivibrator and starts producing the ringing signals. These… Read more »

Transistor Amplifier Circuit-12 Watts

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12 Watts Transistor Amplifier Circuit Description. The circuit shown below is not at all expensive as the amplifier contains only an op-amp and four transistors (easily available from your electronics junk box).Here the op-amp used is uA 741 which produces the required gain.The four transistors are wired as complementary Darlington’s… Read more »

Telephone off-hook indicator

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Description. The circuit depicted here can be used as an indicator when the telephone receiver is off-hook. The circuit can be in corporated with old telephones that does not have such an indicator. The circuit uses a complementary darling to pair using Q1 (2N3904)and Q2 (2n3906) to sense whether the… Read more »

Sensitive Intruder Alarm Circuit

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Intruder Alarm Circuit Description Here is the circuit diagram of an ultra sensitive intruder alarm. The shadow of an intruder passing few meters nearby the circuit is enough to trigger the alarm. Here IC2 uA 741 is wired as a sensitive comparator ,whose set point is set by R6 &R7…. Read more »

Street light circuit.

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Description. The circuit diagram present here is that of a street light that automatically switches ON when the night falls and turns OFF when the sun rises. In fact you can this circuit for implementing any type of automatic night light. The circuit uses a Light Dependent Resistor (LDR) to… Read more »

Single chip FM transmitter circuit

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Single chip FM transmitter Description Here’s a single chip FM transmitter circuit using Maxim semiconductors IC MAX2606. The MAX2606 is a compact, high-performance intermediate frequency VCO specially designed for wireless communication circuits. They have monolithic construction with low-noise and a low-power operation in a compact 6-pin SOT23 packing .Th1s low-noise… Read more »