It is an English Book: Top 10 Simple Electronic Circuits for Beginners:

Generally, success in early projects plays a vital role in the field of electronics for engineering students’ career. Many students quit electronics due to fail in their first attempt. After a few failures, student keeps a misconception that these projects working today might not work tomorrow. Thus, we suggest beginners start with following projects which will give the output in your first attempt and gives motivation for your own work.Before you continue, you should know the working and usage of a breadboard. This article gives top 10 simple electronic circuits for beginners and mini projects for engineering students, but not for final year projects. The following circuits come under basic and small categories.

Top 10 Simple Electronic Circuits for Beginners

The list of top10 simple electronic circuitsdiscussed below are very helpful for the beginners while doing practice, designing of these circuits helps to deal with complex circuits.

DC Lighting Circuit

A DC supply is used for a small LED that has two terminals namely anode and cathode. The anode is +ve and cathode is –ve. Here, a lamp is used as a load, that has two terminals such as positive and negative. The +ve terminals of the lamp are connected to the anode terminal of the battery and the –ve terminal of the battery is connected to the –ve terminal of the battery. A switch is connected in between wire to give a supply DC voltage to the LED bulb.

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.

Simple Temperature Monitor

This circuit gives an indication using an LED when the battery voltage falls below 9 volts. This circuit is an ideal to monitor the level of charge in 12V small batteries. These batteries are used in burglar alarm systems and portable devices.The working of this circuit depends on the biasing of the base terminal of T1 transistor.

When the voltage of battery is more than 9 volts, then the voltage on base-emitter terminals will be same. This keeps both transistor and LED off. When the voltage ofthe battery reduces below 9V due to utilization, the base voltage of T1 transistor falls while its emitter voltage remains same since the C1 capacitor is fully charged.At this stage, base terminal of the T1 transistor becomes +ve and turns ON. C1 capacitor discharges through the LED

Touch Sensor Circuit

The touch sensor circuit is built with three components such as a resistor, a transistor and a light emitting diode.Here, both the resistor and LED connected in series with the positive supply to the collector terminal of the transistor. Select a resistor to set the current of the LED to around 20mA. Now give the connections at the two exposed ends, one connection goes to the +ve supply and another goes to the base terminal of the transistor. Now touch these two wires with your finger. Touch these wires with a finger, then the LED lights up!

Multimeter Circuit

A multimeter is a an essential, simple and basic electrical circuit,that is used to measure voltage, resistance and current. It is also used to measure DC as well as AC parameters. Multimeter includes a galvanometer that is connected in series with a resistance. The Voltage across the circuit can be measured by placing the probes of the multimeter across the circuit. The multimeter is mainly used for the continuity of the windings in a motor.

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

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.

LED Circuit

Light Emitting Diode is a small component that gives light. There is a lot of advantages by using LED because it is very cheap, easy to use and we can easily understand whether the circuit is working or not by its indication.

Under the forward bias condition, the holes and electrons across the junction move back and forth. In that process, they will get combine or otherwise eliminate one another out. After some time if an electron moves from n-type silicon to p-type silicon, then that electron will get combined with a hole and it will disappear. It makes one complete atom and that is more stable, so it will generate little amount of energy in the form of photons of light.

Under reverse bias condition, the positive power supply will draw away all the electrons present in the junction. And all the holes will draw towards the negative terminal. So the junction is depleted with charge carriers and current will not flow through it.

The anode is the long pin. This is the pin you connect to the most positive voltage. The cathode pin should connect to the most negative voltage. They must be connected correctly for the LED to work.

Simple Light Sensitivity Metronome Using Transistors

Any device that produces regular, metrical ticks (beats, clicks) we can call it as Metronome (settable beats per a minute). Here ticks means a fixed, regular aural pulse. Synchronized visual motion like pendulum-swing is also included in some Metronomes.

This is Simple light sensitivity Metronome circuit using Transistors. Two kinds of transistors are used in this circuit, namely transistor number 2N3904 and 2N3906 make an origin frequency circuit. Sound from a loudspeaker will increase and is down by the frequency in the sound.LDR is used in this circuit LDR means Light Dependent Resistor also we can call it as a photo resistor or photocell. LDR is a light controlled variable resistor.

If the incident light intensity increases, then the resistance of LDR will decrease. This phenomenon is called photo conductivity. When lead light flasher comes to near LDR within a darkroom it receives the light, then the resistance of LDR will go down. That will enhance or affect the frequency of the origin, frequency sound circuit. Continuously wood keeps stroking the music by the frequency change in the circuit. Just look at the above circuit for other details.

FM Transmitter using UPC1651

The FM transmitter circuit using UPC1651 is shown below. This circuit is built with UPC1651 IC. This chip is a wide band silicon amplifier, that has a frequency response (1200MHz) and power gain (19dB).

This chip can be worked with 5 volts DC. The received audio signals from the microphone are fed to the i/p pin2 of the chip through the capacitor ‘C1’.Here, in the below circuit capacitor acts as a noise filter.

The modulated FM signal will be available at the pin4 (output pin) of the IC. Here, ‘C3’ capacitor & ‘L1’ Inductor shapes the required LC circuit for building the oscillations. The transmitter frequency can be altered by regulating the capacitor ‘C3’.

This is all about top 10 simple electronic circuits for beginners who are interested in designing their simple electronic circuits . We hope these types of circuits will be helpful for beginners and also engineering students, Furthermore, any queries regarding electrical and electronics projects for engineering students, please give your feedback by commenting in the comment section below. Here is a question for you, what are active and passive components?

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