3 Simple Electronic Circuits

Simple electronic circuits discussed below are very helpful for the beginners while doing practice, designing of these circuits helps to deal with complex circuits.

1. 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.  10 K and 330 K Resistors,  BC 548 and BC 558 Transistors, 3 V battery, 01 mf 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.

2. LED Flasher Circuit

The circuit configuration of 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 at 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.

3.Invisible Burglar Alarm

The circuit of the invisible burglar alarm is built with a photo transistor 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 photo transistor 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 photo transistor, 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 photo transistor turns OFF, permitting the PNP transistor to perform and the buzzer sounds. Fix the photo transistor and infrared LED on the reverse sides with correct position to make the buzzer silent. Adjust the variable resistor to set the biasing of the PNP Transistor. Here other kinds of photo transistors can also be used instead of LI4F1, but L14F1 is more sensitive.