Wednesday, May 18, 2022
Automatic Heat Detector

Automatic Heat Detector

This automatic heat detector circuit uses a complementary pair comprising NPN metallic transistor T1 (BC109) and PNP germanium transistor T2 (AC188) to detect heat (due to outbreak of fire, etc) in...

Light-Activated Switch

Here is a simple circuit of a light-activated switch that automatically turns on the light/lamp at night and switches it off during the day. You do not have to manually operate...

Minuscule LED Night Marker

The minuscule LED night marker presented here is an automatic light beacon that wakes up at night, or when there is not enough ambient light in its environment. Anyone active in...

Logic ‘high’/’low’ Indicator

This logic 'high'/'low' indicator circuit comprises two ICs. One is hex inverter IC 7404 (IC1) and the other is a bistable multivibrator built around timer IC 555 (IC2). A logic probe...

Mixer and Preamplifier for String Instruments

Most of the small musical bands have up to four string instruments like guitars and violins. The signal from the transducers of these instruments should be buffered and sometimes amplified before...
Emergency Light

Portable Emergency Light Using Power Bank

This portable emergency light is based on a DC-to-DC booster module and a power bank. The emergency light is designed to provide sufficient illumination in case of mains power failure. Generally,...

Doorbell-controlled Security Switch

One way to check whether anybody is at home is to ring the doorbell. Burglars too use this very technique. The circuit described here comes handy in such a situation. It...
Low-Cost Intercom Circuit

Low-cost Intercom Using Transistors

This is a circuit for a low cost intercom that is made by using transistors.
Heat Sensitive Switch

Heat Sensitive Switch

At the heart of this heat sensitive switch is IC LM35 (IC1), which is a linear temperature sensor and linear temperature-to-voltage converter circuit. The converter provides accurately linear and directly proportional output...

Little Door Guard

If some intruder tries to open the door of your house, this circuit sounds an alarm to alert you against the attempted intrusion. The circuit (Fig. 1) uses readily available, low-cost components....

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