Photo Modules for PCM Remote Control Systems

Pandi June 10, 2016 2 min read

TSOP 1738 IR remote control receiver

Photo sensors are used to activate / deactivate electronic circuits. The most common Photo sensors used are IR sensor modules. These devices are designed to receive Pulsed Infrared rays from the IR diode from remote handset. Photo modules are used in TV, CD player, and FM receivers etc. to control the functions. By pressing each button of the remote, it is possible to emit IR of a particular frequency and the Photo module senses these pulsed IR rays to change the activity of the device. TSOP 17… Series Photo modules are excellent Infrared sensors for remote control applications.

How about controlling your home appliances like Bulb, Motor etc. just by a single click on your remote that feels cool right!!?? Tenet Technetronics introduces TSOP 1738 breakout board which is an Infrared sensor for remote control applications.

The TSOP 1738 is a member of IR remote control receiver series. This IR sensor module consists of a PIN diode and a pre amplifier which are embedded into a single package. The output of TSOP is active low and it gives +5V in off state. When IR waves, from a source, with a Centre frequency of 38 kHz incident on it, its output goes low.

Internal Block Diagram:

TSOP module has an inbuilt control circuit for amplifying the coded pulses from the IR transmitter. A signal is generated when PIN photo diode receives the signals. This input signal is received by an automatic gain control (AGC). For a range of inputs, the output is fed back to AGC in order to adjust the gain to a suitable level. The signal from AGC is passed to a band pass filter to filter undesired frequencies. After this, the signal goes to a demodulator and this demodulated output drives an NPN transistor. The collector output of the transistor is obtained at pin 3 of TSOP module.

Members of TSOP17xx series are sensitive to different Centre frequencies of the IR spectrum. For example TSOP1738 is sensitive to 38 kHz whereas TSOP1740 to 40 kHz Centre frequency.

Interfacing:

TSOP 1738 can be easily interfaced with the controllers. Photo modules are 3 pin devices. These pins are assigned for +V (5V), –V (GND) and Output. The pin assignment of TSOP 17… series from the front side (projected side) is Pin 1 Ground, Pin 2 + 5V and pin 3 Output. The photo module requires regulated 5V supply. If the supply voltage increases, the device will be destroyed.

Here we are interfacing TSOP with Arduino to display on the LCD, whichever the button is pressed corresponding button name will be displayed on LCD.