Electronics Circuits

Information about Electronics;

In this blog I will be introduce you some simple electronics circuits. Discussed 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;

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.

Working;

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.

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.

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.

Working;

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.

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).

Working;

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’.