This section contains very basic circuits to start with as a new starter in the electronics filed, the idea is to get an idea and to have an basic understanding of the devices and its functions. the basic circuit section encompass minimal parts and time to get better understanding as a beginner.

Rain Detection Circuit

Rain Alarm

The following rain circuit is used to give an alert when it’s going to rain. This circuit is used in homes to guard their washed clothes and other things that are vulnerable to rain when they stay in the home most of the time for their work. The required components to build this circuit are probes. 10K and 330K resistors, BC548 and BC 558 transistors, 3V battery, 01mf capacitor, and speaker.

Whenever the rainwater comes in contact with the probe in the above circuit, then the current flows through the circuit to enable the Q1 (NPN) transistor and also Q1 transistor makes Q2 transistor (PNP) to become active. Thus the Q2 transistor conducts and then the flow of current through the speaker generates a buzzer sound. Until the probe is in touch with the water, this procedure replicates again and again. The oscillation circuit built in the above circuit that changes the frequency of the tone, and thus tone can be changed.

invisivle bulgular alarm

Invisible Burglar Alarm

The circuit of the invisible burglar alarm is built with a phototransistor and an IR LED. When there is no obstacle in the path of infrared rays, an alarm will not generate buzzer sound. When somebody crosses the Infrared beam, then an alarm generated buzzer sound. If the phototransistor and the infrared LED are enclosed in black tubes and connected perfectly, the circuit range is 1 meter.

When the infrared beam falls on the L14F1 phototransistor, it performs to keep the BC557 (PNP) out of conduction and the buzzer will not generate the sound in this condition. When the infrared beam breaks, then the phototransistor turns OFF, permitting the PNP transistor to perform and the buzzer sounds. Fix the phototransistor and infrared LED on the reverse sides with the correct position to make the buzzer silent. Adjust the variable resistor to set the biasing of the PNP transistor. Here other kinds of phototransistors can also be used instead of LI4F1, but L14F1 is more sensitive.

Touch sensitive circuit

The circuit diagram of the touch-based sensitive switch circuit is shown below. This circuit can be built with IC monostable multivibrator mode. In this mode, this IC can be activated by producing a high logic in reply to pin2. The time is taken for the generation of output mainly depends on the capacitor (C1) as well as variable resistor (VR1) values.

Once the touch plate is stroked, then the pin2 of IC will be dragged to a less logical potential like below 1/3 of Vcc. The output state can be returned from low to high on time to make the driver stage of triggering relay. Once the C1 capacitor is discharged, then the loads will be activated. Here the loads are connected to relay contacts and its controlling can be done through relay contacts.

fm transmiter

Rain Alarm

The FM transmitter circuit is shown below which works with 5V DC. This circuit can be built with a silicon amplifier like ICUPC1651. The power gain of this circuit is a wide range like 19dB whereas the frequency response is 1200MHz. In this circuit, the audio signals can be received using a microphone. These audio signals are fed to the second input of the chip through the C1 capacitor. Here, the capacitor acts like a noise filter.

Automatic wash room light


Have you ever thought of any system ever existed that is capable of switching on the lights of your washroom the moment you enter into it and switching off the lights when you leave the bathroom?

Is it really possible to switch on the bathroom lights by just merely entering the bathroom and switch off by just leaving the bathroom? Yes, it is! With an automatic home system, you don’t really need to press any switch at all, on the contrary, all you need to do is open or close the door – that’s all. In order to get such a system all you required is a normally closed switch, an OPAMP, a timer, and a 12V lamp.


The circuit configuration of an LED flasher is shown below. The following circuit is built with one of the most popular components like the 555 timer and integrated circuits.This circuit will blink the led ON & OFF at regular intervals.

From left to right in the circuit, the capacitor and the two transistors set the time and it takes to switch the LED ON or OFF. By changing the time, it takes to charge the capacitor to activate the timer. The IC 555 timer is used to determine the time of the LED stays ON & OFF.

It includes a difficult circuit inside, but since it is enclosed in the integrated circuit. The two capacitors are located on the right side of the timer and these are required for the timer to work properly. The last part is the LED and the resistor. The resistor is used to restrict the current on the LED. So, it won’t damage

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