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    TSOP 17… Series Photomodules are excellent Infrared sensors for remote control applications. These IR sensors are designed for improved shielding against electrical field disturbances.
    TSOP 1738 Photo module Design notes

    TSOP 17…. Series Photomodules are miniature IR sensor modules with PIN photodiode and a preamplifier stage enclosed in an epoxy case. Its output is active low and gives +5 V when off. The demodulated output can be directly decoded by a microprocessor. The important features of the module includes internal filter for PCM frequency, TTL and CMOS compatibility, low power consumption (5 volt and 5 mA), immunity against ambient light, noise protection etc. The added features are continuous data transmission up to 2400 bps and suitable burst length of 10 cycles per burst.

    Inside the Photo module

    The photo module has a circuitry inside for amplifying the coded pulses from the IR transmitter. The front end of the circuit has a PIN photodiode and the input signal is passed into an Automatic Gain Control(AGC) stage from which the signal passes into a Band pass filter and finally into a demodulator. The demodulated output drives an NPN transistor. The collector of this transistor forms the output at pin3 of the module. Output remains high giving + 5 V in the standby state and sinks current when the PIN photodiode receives the modulated IR signals. Block diagram is given in Fig 1

    Pin assignment

    Photomodules are 3 pin devices. These pins are assigned for +V,–V 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.

    The pin assignment (Front view) of some common Photomodules

    Type pins 1 2 3 Response frequency
    TSOP 1730 G 5V OP 30 kHz
    TSOP 1736 G 5V OP 36 kHz
    TSOP 1738 G 5V OP 38 kHz
    TSOP 1756 G 5V OP 56 kHz
    TSOP 1236 G 5V OP 36.7 kHz
    TSOP 1838 OP G 5V 38 kHz
    TSOP 1138 G 5V OP 38 kHz
    TK 1836 OP G 5V 36 kHz
    SFH 506-38 G 5V OP 38 kHz
    RPM 7238F OP G 5V 37.9 kHz

    Design considerations

    For the proper functioning of the Photo module, 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.

    Photo module design is given in Fig.2

    ask a question

    53 Responses to "TSOP 1738 Photo Module Design Notes"

    1. Hi. I am studying tsop 1738 i am getting output of tsop as continuous 5 volt when there was no obstacle and when obstacle came its voltage get lower down to 1.8v approximately for very short time and again became 5 v . i get square wave at the o/p of tsop when obstacle appear for short time and average vtg is remain 5 v even if obstacle is present

    2. The IR modules are designed to receive pulsed IR rays.TSOP 1738 accepts only 38kHz. It will not do better if the frequency is below or above 38kHZ.It will not responds to continuous IR rays without pulsations. As you observed, when it gets IR pulses, O/P becomes Zero. The time gap between two pulses should match with the module otherwise output will go high again.TSOP 1738 requires regulated 5 volts with a capacitor close to its pin 2. If supply voltage exceeds the limits sometimes O/P will not be Zero

      • Nitin Ajgaonkar says: on January 4, 2012 at 4:21 pm


        I want to build Remote control extender circuit, with TSOP 1738 and TIL38 IR Emitter. I am not getting TIL38 in mumbai, Can you guide me where can i get the same.

      • sbangar672 says: on September 6, 2012 at 1:39 pm

        i want to use sony tv rmote control with ir sensor, which sensor should i use

    3. it remain low for very short duration of time even if obstacle is present continuously

    4. What type of IR pulses used.Mention the circuit or Remote used

      • Nitin Ajgaonkar says: on April 3, 2012 at 5:09 am

        I want to build Remote control extender with TSOP module for Tatasky DTH. pls give good circuit.

    5. hi iam studying in bsc electronics . now doing a project ELECTRONIC WATCH DOG using tsop1738. i got output but is not proper. frequency of transmitter is almost 37.33 khz . what shoud i do? plz kindly help me as soon as possible. please send the answer to my id mahesh.adka@gmail.com.plz

    6. hi also plz reply me detailed working of tsop 1738. pleas

    7. pls reply me

    8. i got the output continously low when obstacle present using ic555…..But when i use the atmega 16 to generate the square wave it output remain low for very short duration of time even if obstacle is present not continous as in case of ic555

    9. The problem is with 555 Astable. If the timing capacitor is leaky or resistor has different tolerance, frequency will change,.TSOP 1738 requirs exact 38kHZ pulses. Test it with a TV remote

    10. what is the ideal otput of tsop when obstacle appear is it to be continuously low till obstacle present or as a low trigger

    11. Outout of TSOP1738 is active low when 38Khz IR pulses are available. It gives zero volts. When there is no IR rays, it goes to +5 volt 5 mA and remains as such

    12. Sir please clear that even after 38khz frq.(checking with CRO), output of tsop is high & it goes low for very short period & return to high again.Somwhere you explain that The time gap between two pulses should match.What that means.I think every body is not understanding why it is going high again even freq is correct.

    13. Sorry for again but why we are not acheaving the output of TSOP low when 38Khz pulses are available.where we are doing wrong?
      I was suffring with this problem so for latching its output, after any intrusion I added a latch circuit. At that time I managed for my requirement but it should clear to me that where is problem.
      I m understanding that U will irritate for repeating a same question by many but sir please understand us too…..

    14. I will post a simple latch circuit using TSOP1738. Try that

      • Ngoc Duy Nguyen says: on October 30, 2013 at 5:14 pm

        Dear Sir,
        As you said, where can I find “a simple latch circuit using TSOP1738”? Please let me know a link. Thank you

    15. hi sir, still waiting for your circuitry. Here i want to clear that i was using 1838 instead of 1738. both operated on 38 khz.if wrong please guide. Thanks

    16. Your problem is with the sensor. Pin connection of TSOP 1838 is 1-OUTPUT, 2-GND,3 +5V
      I have posted a circuit using phototransistor-Electronic gate keeper

    17. sir my project title is’DC MOTOR CONTROL USING IR DATA CMMUNICATION’.sir i dont have d ckt diagram…can u please help me out wid it…

    18. hello sir,
      I am working on ir remot control.so how can i decode the output of tsop1738 using microcontroller 89c51.

    19. sir,
      Im using tsop with p89v51d2 micro controller …….. i need to switch relay using remote for that im using tsop…….. how can i seperate frequency using remote

    20. dear sir,
      I assembled remote circuit with TSOP1738 operated by TV remote which was published in EFY magazine. I added this remote circuit to the 12V battery operated LED lights (40nos of white LED). In my cabinet I fixed TSOP1738 near to the LED and TSOP1738 is connected to the board by external wire around the length of 15cm. The 100microfarad capacitor fixed in the board not nearest to the TSOP1738. I have a problem in my switching operation. When passing the IR signal using remote it turns on LED but again passing the IR signal it does not turn off the LED properly(require 5-10 operation).

    21. i need an IC which can tell the exact position of vehicles behind my car.Also i want it to sense if if car is coming towards e..

    22. hello sir,
      i m using tsop 1838 in place of 1738,…i m making a project of turning device on/off using tv remote,…bt when i check for output frm reciever it drop to 3.9 from 4.8 jst when pressing remote ,.
      can u plz tell me what problem i m facing ,..is the problem with reciever or something else i can do,.?

    23. hello sir,
      i m using tsop 1838 in place of 1738,…i m making a project of turning
      device on/off using tv remote,…bt when i check for output frm
      reciever it drop to 3.9 from 4.8 jst when pressing remote ,.
      can u plz tell me what problem i m facing ,..is the problem with
      reciever or something else i can do,.?

      • ram krishna says: on February 26, 2012 at 6:06 am

        hey visus if u came to know about the solution of above problem please reply…i am facing the same problem the voltage level changes are small..in my case it is …4.9 to 3.8..appx same as yours…pls help…

      • Felix Nyirigira says: on June 7, 2012 at 8:30 pm

        hey visus please me too i have the same project and facing the same problem, please i need your collaboration between us in order to help eachother

    24. hello sir,
      i need analog output from Tsop(or any other IR detector) to measure distance from the obstacle…is this possible with any tsop or any other ir detector…?

    25. sir, how to protect from external magnetic field…

    26. SIR,actually i am using signal of TSOP to print number of obstacles detected…but when i am trying it is increasing values more than 1,sometimes 2 or 4…
      please reply what is the fault..
      I have to submit my project tommorow..so if possible reply fast.
      THANKING you

    27. sir we are doing our project named AUTOMATIC SCORE BOARD FOR BASKET BALL…which type of sensor is used for identifying different points such as free throe.two point..etc….
      can IR sensor be used for sensing these point or which type of sensor is used for sensing?????
      reply for this project

    28. PIPALIYA KULDEEP says: on February 13, 2012 at 3:28 pm

      Hello sir
      i want to make wall follower so to generate 38khz which thing ,i can use???

    29. hi sir. can i interface o/p of tsop1738 directly to port 1 of 8051microcontroller or do i hav to use anything in between??? also could you plz send me a simple ckt with ir led and tsop 1738…

    30. Dear sir,
      i am facing the problem while using the tsop1738 the voltage level changes are small..in my case it is …4.9 to 3.8..
      why it is so???
      what should be the ideal output of the tsop ??
      pls reply

    31. Hello sir, I use tsop 1738 in my automatic room light control with visitor counter.It just stic on 0 V whether ir LED is connected or not..i cant understand problem.
      What can I do to overcome this problem?pls reply me asap..

    32. Shankar mohokar says: on March 19, 2012 at 6:17 pm

      Hi sir ,
      tsop 1738 sensors are damaged after few working , what is reasone behind it,

    33. hello sir,
      i want to use tsop1738 in our project.
      but just tell me how can i design a circuit using single lm555 to overcome the following two problems and
      give the transmitter side design details.
      plz rply me

      1.Burst length must be 10 cycles per burst or more.(lm 555 can be used)
      2. Between each 10 to 70 cycles, a gap time of 14 cycles is necessary to reset the module.(how to deal with this problem.should we use another lm555??)

      (we do not have uc in our project.)

      plz rply as early as possible.

    34. varsha solanki says: on April 29, 2012 at 6:53 pm

      can u please tell me various applications of TSOP1138 IR detector?



    36. Hey sir,
      How can i receive a ir modulated signal without being demodulated..
      the ir receivers demodulate the ir signal and just give out PWM on or OFF state, but i need pwm of the carieer frequency itself .few websites suggested using photodiode we can get this..but it failed..
      please let me know if u can help out with this
      Thank you .

    37. Felix Nyirigira says: on June 7, 2012 at 8:21 pm

      hey! i’m studing electronics and telecommunication in IPRC Kigali and i have the project of IR remote switch. so i want help how can i increase the distance between transmitter and receiver?

    38. where buy tsop 1838 in indonesia?
      please help me

    39. how i write refrence on remote tester ussing ir sensor 1738

    40. sir, i have to assign a particular task for indiviadual numbors of tv remote, but at reciever how can we know that this particular number has been pressed, if we connect it to 8051 mc. sir, please describe about it clearly, it will very helpful to me. thanking you sir.

    41. sir, iam getting trouble with ir sensor when it was working in outside (in the sunlight). the circuit with 16f72 & 1738 sensor is working well when it was working inside the room. is there any method to screen the weak ir signals from sunlight.

    42. SIR…..
      can u plzz….. explain us how to make a self IR remote control for multiple applications.
      with a circuit diagram(both receiver and transmission sections)
      and also how to generate different codes or pulses at the receiver section …………….plzz reply HOPING U WILL

    43. Please tell me where can i find tsop1738 in schematic?
      i could not find in Proteus even unable to find in eagle please help me

    44. please tell me about tsop1738 operating range

    45. saad jaha kayani says: on December 8, 2015 at 5:45 pm

      i have TSOP 1738 ,its giving me high signal but not working on any remote when press any button

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