Simple Remote Control

Here is the simple example of a Television remote control working used in our day to day life.

Components Required:

1) Breadboard

2) 470 ohm resistor

3) LED (Any Color)
4) Phototransistor

5) 9Volt Battery 

Procedure:

• Connect the circuit as shown in the circuit diagram below.
• The Phototransistor remains OFF until a IR light is incident on it.
• Hence the LED connected in series to it also remains OFF.
• Now take your television remote which consists of a IR LED.
• Pointing towards the phototransistor press any button on the remote.
• When the button is pressed the remote emits IR and forward biases the phototransistor and lights the LED.
• Based on the input from the remote you can visually see a rhythmic pattern in the LED.
• Now check with some other button inputs, LED glows in various patterns and with some small variations in timings.

Circuit Diagram:

Figure 1: Simple Remote Control Circuit simulation made in Multisim

Explanation:

They are digital pulses sent from the remote to the receiver in the television. Based on those digital pulses received in the receiver end the corresponding changes in channels or volumes happens. For every ON pulse produced by the remote the LED glows and for every OFF pulse the LED dims. 

Pulses produced by the remote are based on timings. When the LED blinking frame rate is greater than 150FPS (Frames per second) our normal human eye cannot detect its blinking and recognizes it as a ON pulse even though it blinks. When it ranges in the normal frame rate our eye detects its blinking. In some cases when the frame rate is nearer to 150FPS we may only see the dimming & brightening of the LED.