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.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.
Reference of above article-www.engineersgarage.com
Reference of above article-www.engineersgarage.com
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