Query about Infrared Receiver TSOP 1738

[reubenn]

tsop1738

hello everybody, i'm currently working on my final year project
this is the idea it is based on:
a circuit (transmitter) mounted on a door is made to send a pulsed IR beam across to a circuit (receiver) mounted on the wall adjacent to the door.
a microcontroller monitoring the receiver circuit knows when the beam is interrupted, if the door is opened,and is used to place a call using a landline telephone.

Now, i'm using this circuit for the transmitter part : refer page 9 of the attached pdf

For the receiver part refer page 10 of the attached pdf please.

What i wanted to know is whether the carrier generated by the second 555 IC should be exactly square and exactly 38 kHz, so that the TSOP 1738 Receiver recognizes it?

The datasheet of TSOP 1738 has been included in the attached pdf

 

[reubenn]

tsop1738 ir receiver

Also, when somebody picks up a landline telephone and dials a number, he knows when the called party has picked up the telephone.
Im using a microcontroller in the above circuit. Lets say the system is switched ON and an intruder breaks into the house. Using the process called "pulse dialling"(a system of dialling used by the earlier phones still available on modern phones, see here to understand properly :
https://en.wikipedia.org/wiki/Pulse_dialing), the microcontroller can dial a pre-determined number.
Trouble is , how does the microcontroller recognize that the called party has picked up the phone and play the voice message?
What are the signals involved when a call is placed and connected ?

 

[Audioguru]

tsop 1738

The 38kHz must be somewhere near 38kHz. The datasheet has a graph showing sensitivity loss with frequency difference.

The TSOP reduces the gain of the receiver when it detects 38kHz that does not have the proper 10 cycles to 70 cycles of 38kHz followed by a gap time at least 14 cycles of silence.

Some telephone exchanges send a pulse of opposite DC polarity to the sending end when the receiving end answers.

 

[reubenn]

tsop 1738 ir receiver

Can somebody please tell me how a call is placed using a landline phone, and what signal is sent back to the calling party when the called party has picked up the phone?

 

[Audioguru]

ic tsop1738

Can somebody please tell me how a call is placed using a landline phone, and what signal is sent back to the calling party when the called party has picked up the phone?

Please do not barge in and hyjack this thread about IR receivers.
Please make your own thread about how a telephone system works or look in Google to see how the telephone system works differently in many countries.

 

[reubenn]

working of tsop1738

what happens if the TSOP 1738 receives a signal that is continuously at 38kHz, i.e. a signal that is not pulsed, like in my first post?
Will the o/p of TSOP be continuosly high ?

 

[Audioguru]

infrared receiver ic

what happens if the TSOP 1738 receives a signal that is continuously at 38kHz, i.e. a signal that is not pulsed, like in my first post?
Will the o/p of TSOP be continuosly high ?

The output of a TSOP IR receiver IC goes low when it receives 38kHz IR. If the IR is continuous then it thinks it is interference from compact fluorescent light bulbs then its AGC reduces the gain. If the IR source is close enough or is strong enough then the output will still remain low.

 

[reubenn]

ir receiver circuit using tsop

The TSOP 1738 datasheet states that the burst length should be 10 cycles/burst or longer, OR between 10 cycles and 70 cycles and a gap time of at least 14 cycles is necessary.
1 "cycle" here means inverse of 38kHz, right?
That works out to 26.32usec
40(average of 10 and 70) cycles works out to an ON time of 1.05 msec.
20(taking a round figure above 14 cycles) works out to an OFF time of 0.526 msec.
am i right in these conclusions?

3>> Going by the above calculations, i've changed the values of the timing resistors connected to the first IC555.

4>> The first IC 555 is in astable mode, and the second in astable mode, right?

Despite doing all this, the o/p of TSOP is not present.
What can be wrong ?

5>>Should the emitting infrared diode be the one specified in the datasheet, i.e. TSAL 6200, or will any infrared emitting diode do?

6>>How dp i check whether the TSOP is not faulty ?

 

[Audioguru]

tsop ir

If you have one 555 making 40 cycles of 38khz and another 555 making the 38kHz oscillator pause for 0.526ms then the TSOP1738 should have an output low for 1.05ms and an output high of 0.526ms.

Point a working TV remote control at the TSOP and see its output change.

 

[reubenn]

tsop1738

Finally, i got the o/p of TSOP 1738.Just had to tinker about a bit with the pots connected to the 555's.
As "Audioguru" says, its o/p is high when no signal is detected, and low, when there's a 38kHz signal.
Thanx to "Audioguru".

 

[evans]

tsop 555 timer

i am doing my project on the ir detection and position displaying on the TV. i have chosen LM555 as a moving source of 38khz, i will use tsop 4138, 1738 or 4338 for detection. among the three reciever modules, which one is appropriate for the 38khz from LM555 at distance 2.5metera?

 

[GSHYAMIITIAN]

data sheet for tsop1738 ir receiver module

what is the range of tsop ?????????

 

[Audioguru]

tsop1738 ir receiver circuit

what is the range of tsop ?????????

The TSOP1738 and many more IR receiver ICs are used in consumer products. Indoors without sunlight they have a range of 10m to 15m when an IR sender uses 1A pulses in bursts of data. The AGC reduces the gain when continuous 38khz pulses are received and then the range is only 1m. If the IR pulses are less than 1A then the range is less.