Will This work Fine? -40 KHz IR Transmitter and Receiver

Discussion in 'General Electronics Chat' started by neba3939, Feb 28, 2016.

Will the transmitter transmit 40kHz and receiver detect the circuit fine?

  1. Yes

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  2. NO

    2 vote(s)
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  1. neba3939

    Thread Starter New Member

    Feb 28, 2016
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    I am designing this IR transmitter and Receiver... I am thinking of transmitting 40kHz. I have attached the schematics, for both transmitter and receiver. I am not sure if this will work fine, please let me know.
     
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  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    For the receiver, Q1 should be an NPN type.

    ak
     
  3. DickCappels

    Moderator

    Aug 21, 2008
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    Didn't check the values of the timing components in your oscillator, but if your transmitter sends at the same frequency the the receiver expects and you connect an IR LED to the output of the NE555 wiith appropriate drive circuit -like a resistor, it has an excellent chance of working, provided you heed AnalogKid's advice.
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    You need a Npn transistor, the ic has an internal pullup resistor, if your using a pnp your transistor is drawn upside-down.
     
  5. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    I didn't check the calculations for frequency. Others have already commented on that. However, your planned transmitter will produce a steady signal of 4o kHz. The receiver will receive it, but because the signal is steady, its gain (AGC) will be turned down and sensitivity (i.e., range) will be low. If you want decent range, you need to pulse the 40 kHz "carrier" as shown in the datasheet for the TSOP1740:
    upload_2016-2-29_10-10-58.png
    That pulsing can be done without another 555 or both things can be done with a 556 chip. What range do you need?

    John
     
  6. neba3939

    Thread Starter New Member

    Feb 28, 2016
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    Thanks for the reply..
    I am thinking of using the circuit in a room, so i would say the range should be approximately 32feets
     
  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    For 32 feet, you will need to pulse it, in my experience.

    John
     
  8. neba3939

    Thread Starter New Member

    Feb 28, 2016
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    How would i be able to pulse. This is my first time doing this.. Can you help me do it. What do i need to do
     
  9. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Here is what I did many years ago. I don't have a nice schematic to show you, but here is what was simulated:
    upload_2016-2-29_16-42-25.png

    Here's the simulation:
    upload_2016-2-29_16-43-39.png

    I also did a version with the 556 chip, which is just two 555's inthe same package with fewer pins.

    The way it works is the 555 on the right turns the 555 on the left on or off with the reset pin. The 555 on the left needs to be set at your 40 kHz. The one on the right at the repeat ("modulation") rate. There are other ways to do it too, such as using the trigger pin, but I liked this circuit better.

    I actually never used that circuit as I moved to a PIC 12F509 microcontroller to do it; although, the circuit was built on a breadboard and worked. That was my first PIC project, and I never regretted making the change.

    John
     
    Last edited: Feb 29, 2016
  10. neba3939

    Thread Starter New Member

    Feb 28, 2016
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    Thanks i will try that.. i will let you know what happens
     
  11. jpanhalt

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    You probably WILL need to adjust some of the timing resistor values to get your frequency and period spot on. Luckily, TSOP's are pretty forgiving.

    John
     
  12. neba3939

    Thread Starter New Member

    Feb 28, 2016
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    I tried to build what you gave me jpanhalt... but it exteneded the range a little bit. but the range didnt get big as i expected it... is there anyway that i can extend the range. plus if you can, can you tell the value of timing resistors on your last circuit. thanks
     
  13. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    My timing resistors were set for 38 kHz. I understand you want 40 kHz. What values did you use? What range did you get and what value for R3 did you use? What IRED are you using (part number please)?

    John
     
  14. neba3939

    Thread Starter New Member

    Feb 28, 2016
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  15. neba3939

    Thread Starter New Member

    Feb 28, 2016
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    I am waiting for your help jpanhalt
     
  16. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    why are you using 56k Hz? Did you change your part number to TSOP1756? If not, then you loose 60% of sensitivity for each 10% error in frequency.

    Also, your current emitter from Jameco has 20+/-degree focus (40-degree cone). That means, the beam drops to 50% intensity by the time you get to 20-degree from mid-line of the beam. In other words, your beam is spread by 40-degrees of cone angle. that is ok if your aim is not very good with the IR beam but bad if you are trying to extend range. Note tht the power of the beam dissipates by the square of the distance. The smaller your cone angle is, the greater your initial power will be per square centimeter.

    Why don't you try making the calculation of how much power per square meter reaches a wall 32 feet away if your emitter is 20 degree, 10 degree and 5 degree.

    good luck.
     
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