This document describes an infrared (IR) switch and remote control circuit. It discusses how IR light works and its applications, including in TV remotes. The circuit uses an IR detector tuned to detect pulses at 38kHz from an IR LED in the remote control. The detector circuit has four stages: 1) IR detection, 2) buffering the signal, 3) generating an on/off command, and 4) toggling an LED switch on or off. The remote control circuit uses a 555 timer oscillator to pulse the IR LED at 38kHz, matching the detector. Pressing the remote will toggle the LED switch.

1. Indian Institute of Technology
Hyderabad
IR SWITCH & REMOTE
CONTROL
SUNIL KUMAR REDDY
SREERAM

2. INFRARED RAYS
 Infrared (IR) light is electromagnetic radiation with
longer wavelengths than those of visible light.
 Its wavelength ranges from 700nm-1mm.
 Infrared radiation is used for short and medium range communications
and control.
 Some systems operate in diffuse mode,also called scatter mode. This
type of system can function when the sourceand destination are not
directly visible to each other.
 Unlike radio-frequency (RF) wireless links, IR wireless cannot
passthrough walls. Therefore, IR communications or control is generally
not possible between different rooms in a house.
 This technology is used in telivisionremote-control box.

3. In this project we will construct an infrared switch and remote control.
The switch can be turned on or off by shining infrared light on to the
sensor.
IR DETECTOR SWITCH
CIRCUIT HAVING THE IR DETECTOR AND LED

4.  The IR detector is used in this project is tuned to detect IR radiation
pulsed at a specified frequency only.
 This is the frequency at which the standard TV remotes work, hence
a TV remote also can be used instead of the IR LED based remote.
 Since we are not modulating any additional information with the IR
pulses the detector can be used to operate only one switch..
 The irdetector is tuned not to respond to stray IR coming from
natural light or any other source like tube light etc in your home.
 To transmit the radiation we use irled in remote control.

5. REMOTE CONTROL
CIRCUIT HAVING IRLED
The IR remote circuit shown here is a simple 555 based multi vibrator,
which can oscillate at 38KHz by controlling the trimport.

6. There are four different blocks/stages in the detector circuit, namely 1) IR
detection 2) Buffering of the Signal 3) Generating the on/off command and
turning the switch ON/OFF.
1.The detector circuit uses an IR detector TSOP 1738 commonly available
in the market. This is tuned to detect IR pulses at 38Khz frequency and also
it tuned not to respond to stray IR coming from natural light or any other
source like tube light etc in your home.
2.Since IR detector can produce a sequence of signals when it detects IR
radiation we are using a buffer which will, sort of accumulate signal received
for about 1-1.5 sec and generate on signal. We are using CD4049 to do the
buffering. The signal is send to the next stage
3.In this stage a 555 is used mono stable signal generator ,to generate a
signal and prevent any further signal for a short period of 1 sec.
4.In this block we are using a flip-flop 74LS74 to toggle the switch every time
we get a signal from the previous stage