Infrared switch and Remote mini project

In this project we will construct an Infrared switch and remote control. The switch can be turned on or off by shining infrared light, using and LED, on to the sensor. The IR detector is used in this project is tuned to detect IR radiation pulsed at a frequency of 38 KHz. 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.

Circuit Diagram

IR detector circuit

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 and4) 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.

IR Remote switch Circuit

shown here is a simple 555 based multi vibrator, which can oscillate at 38KHz by controlling the trimport.