Long range IR using transistor and 555 timer astable mode

The commonly used IR transmitter has a limited range. This circuit based project can be used to increase its range. This is achieved by amplifying the signal which is fed to the IR Led for transmission.

Major function in assisting IR LED to increase its range is carried out by two devices:

1. BC 547

2. NE555 Timer.

BC 547 is a NPN transistor which is generally used in common emitter configuration for switching and amplification purposes. In the circuit, the transistor works in its usual configuration and is using a voltage divider procedure for biasing.NE555 is a popular 555 timer used for several applications as it generates pulses of accurate width. It can be operated in monostable and astable modes. Being an IC, this timer reduces the complexity of the circuit by a certain extent. The modes can be switched from monostable to astable and vice versa simply by adjusting resistor placement to it. Let’s find out how this circuit uses the timer and the transistor to increase range of IR LED.

This project is based on NE555 which generates pulses of a certain frequency which depends on the value of Resistors R3, R4 and Capacitor C1. NE555 is thus configured to operate in astable mode. The output of NE555 is fed to the base of Transistor T1 (BC 547) which acts as an amplifier. The amplified output from T1 appears across a load Resistor R4 (1k) connected to its collector. Resistor R3 (330) acts as base resistor to check the base current. These amplified pulses are finally provided to the IR Led for transmission.