555 Timer - Astable mode

Astable operation is a free running oscillator without any stable state. The threshold terminal (pin 6) and the trigger terminal (pin 2) are connected together to form a self-trigger. This ensures that an external trigger is not required for its operation.

The pulsewidth is determined by two external resistors and one capacitors using the constant 0.693(R1 + 2R2)C1

555 Timer - Monostable mode

Monostable operation have one stable state and an unstable state. By default, the circuit rests in its stable state but it can be switched over into its alternate state whenever there is an external trigger on its trigger terminal(pin 2) where it will stay for a period of time before moving to its default state. The trigger voltage must be below one-third of the supply voltage(VCC/3). 

RF transmitter and Receiver circuit

  Whenever there is an input from the push button, it is received by the encoder (HT12E) as parallel data. It is converted to a serial data and sent to the transmitter. This data is modulated by the transmitter and sent at a frequency of 433MHz. The transmitted signal is picked up by the receiver at the same frequency as that of the transmitter and demodulated before being transferred to the decoder (HT12D). HT12D compares the serial input data three times continuously with the local addresses.

If no error or unmatched codes are found, the input data codes are decoded and then transferred to the

Light Activated Switch Using LDR and Motor

The DC motor in this circuit serves as the output which is switched off or switched on by the presence or absence of light on the surface of the light dependent resistor (LDR).

Thermistor

A thermistor is a type of resistor whose resistance changes rapidly with temperature. The word 'thermistor' is derived from "thermal" and "resistor". They are temperature sensors.

Picture of a thermistor

Thermistor symbol

Light Dependent Resistor

What is LDR

Light dependent resistor is also referred to as photo-resistor, cadmium sulfide (cds) cell, photoconductor or photocell. It is an electronic component whose resistance changes with the light intensity falling on it. It has the ability to detect the presence or absence of light and this detection reflects on its resistance value.This allows them to be used in light sensing circuits. Their ability to produce a very large change in

Resistor

Resistor Basics

Resistor is an electronics component that offers opposition to the flow of electrons. This resistance have a specific electrical resistance. Resistors are primarily used for current limiting, voltage division and similar functions.

The resistance of a resistor is measured in ohms using the Greek symbol omega (Ω).

Picture of a resistor