Simple Infrared (IR) Remote Control Circuit

Controlling household electrical gadgets or any electrical equipment remotely can be fun.  Controlling gadgets like a TV set or a DVD player through a remote may look pretty common to us and we are very used to with the experience, however for controlling many other domestic equipment like a water pump, lights etc we are compelled to walk around for implementing the switching.

The article is inspired by our usual TV remote concept and has been applied for controlling other house hold electrical appliances remotely.  The circuit facilitates and helps the user to do the operations without moving an inch from his resting place.

The whole circuit of the proposed IR remote control may be understood by studying the following points:

Referring to the figure, we see that the entire layout consists of just a couple of stages viz: the IR sensor stage and the fkip flop stage.

Thanks to the highly versatile, miniature IR sensor unit which forms the heart of the circuit and directly coverts the received IR waves from the tranamitter unit into the relevant logic pulses for feeding the fllip flop stage.

The sensor basically consists of just three leads viz: the input, the output and the biasing voltage input lead. The involvmant of only three leads makes the unit very easy to configure into a practical circuit.

The sensor is specified for operating at 5 volts regulated voltage which makes the inclusion of the 7805 IC stage important. The 5 voltage supply also becomes useful for the flip flop IC 4017 and is appropriately supplied to the relevant stage.

When a IR signal becomes incident over the sensor lens, the inbuilt feature of the unit activates, triggering a sudden drop in its output voltage.

The PNP transistor T1 responds to the negative trigger pulse from the sensor and quickly pulls the positive potential at its emitter to the collector across the resistor R2.

The potential developed across R2 provides a positive logic high to the IC 4017 input pin #14. The IC instantly flips its output and changes it’s polarity. 

The transistor T2 accepts the command and switches the relay according to the relevant input provided to its base.

The relay thus switches the connected load across its contacts alternately in response to the subsequent triggers received from the IR transmitter unit.

For the sake of convenience the user may use the existing TV remote control set unit as the transmitter for operating the above explained control circuit.

The referred sensor is well compatible with all normal TV or DVD remote control handset and thus can be appropriately switched through it.

The entire circuit is powered from an ordinary transformer/bridge network and the entire circuit may be housed inside a small plastic box with the relevant wires coming out of the box for the desired connections. 

Parts List  

The following parts will be required for making the above explained infra red remote control circuit:

R1, R3 = 100 ohms,

R2 = 100K,

R4 = 4K7,

R5 = 10K,
C2 = 470uF/25V

C1, C4= 22uF/25V,

C6 = 4.7uF/25V,

C3 = 0.1, CERAMIC,

C5 = 1000uF/25V,

T1 = BC557B

T2 = BC547B,

ALL DIODES ARE = 1N4007,

IR SENSOR = TSOP1738 image: Vishay

 IC1 = 4017,

IC2 = 7805,

TRANSFORMER = 0-12V/500mA,

Prototype image courtesy: Raj Mukherji

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