TSOP IR Receiver

The TSOP is a 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 is incident on it, its output goes low. 
Lights coming from sunlight, fluorescent lamps etc. may cause disturbance to it and result in undesirable output even when the source is not transmitting IR signals. A bandpass filter, an integrator stage and an automatic gain control are used to suppress such disturbances.

TSOP module has an inbuilt control circuit for amplifying the coded pulses from the IR transmitter. A signal is generated when PIN photodiode 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.


Available types for different carrier frequencies

    Type                  fo                       Type            fo
TSOP1730          30 kHz               TSOP1733    33 kHz
TSOP1736          36 kHz               TSOP1737    36.7 kHz
TSOP1738          38 kHz               TSOP1740    40 kHz
TSOP1756          56 kHz


For the proper functioning of the TSOP, it is necessary to consider some important aspects.
1. Supply voltage should be + 5 Volts. For this, a 5.1 volt Zener must be connected to the +V pin and ground.
2. A 100 uF capacitor should be connected to the +V pin as a buffer and filter capacitor. This will suppress the power supply disturbances.
3. Carrier frequency should be close to the center frequency of the band pass filter. 38 kHz in the case of TSOP 1738.
4. Burst length must be 10 cycles per burst or more.
5. Between each 10 to 70 cycles, a gap time of 14 cycles is necessary to reset the module.
6. DC lights such as tungsten bulb and daylight affects the functioning of the photo module.

7. Signals from Fluorescent lamps with electronic ballast will affect the working of the photo module.
8. Continuous IR signal (non- pulsed) will disturb the photo module and it will not responds to it.


TSOP datasheet click here 



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