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Discussion in 'Electronic Projects Design/Ideas/Reviews' started by Abeer_engjbr, Feb 10, 2008.

  1. Abeer_engjbr

    Abeer_engjbr New Member

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    Hi
    I connected the IR Repeater circuit part by part but:
    1) The Led that must be off for testing was on with no input ( Why is that?)

    2) The oscillator has no clear signal on the screan ( I connected it on the 2.2k resistor), but when I point the ir signal at the photodiode as I get closer to it the amplitude became larger.

    3) I know that the function of the photodiode is to convert ir signal to current in order to deal with it in an electronic way rather than electromagnetic way, but , on the hand when I tryed to measure the current that is passing through 3.3k resistor , there was a very small reading (0.006mA) after pointing the ir signal , is that true? or does this indicates that the photodiode does not work properly? How can I test a photodiode?

    Please Answer ASAP, I need to try your suggestions.
    Thanks.
     
  2. Abeer_engjbr

    Abeer_engjbr New Member

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  3. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The circuit does not have a photo-diode. A photo-diode has two wires.
    The circuit has a TSOP1738 IR receiver IC. It has three wires.
    Maybe you used a photo-transistor that has three wires and would cause your symptom.

    The output of the IR receiver IC is high when it does not receive a signal. Then the first transistor is turned on which resets the 555 so it does not run and makes its output low so the output transistor does not turn on the LEDs.
     
  4. dave

    Dave New Member

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  5. Abeer_engjbr

    Abeer_engjbr New Member

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    I used a TSOP1738, I bought it specificaly last week, maybe i said photodiode but i ment TSOP1738 IC, any way i need to know why i the Led on when i test the circuit directly after i connect the 12 V to the circuit, What should I do to test the 3 stages?
     
  6. aliali88

    aliali88 New Member

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    Thanks alot for all
     
  7. Abeer_engjbr

    Abeer_engjbr New Member

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    Why are you saying that?! Thank you any way!
     
  8. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Start testing at the output:
    1) Connect the base of the output transistor to 0V and the LEDs should turn off.
    2) Connect pin 4 (RST) of the 555 to 0V and the LEDs should turn off.

    Maybe you connected the pins of the TSOP backwards.
    Maybe you connected the zener diode backwards so it produces 0.7V instead of 5.1V.
    Maybe you connected the pins of the transistors backwards.
     
  9. Abeer_engjbr

    Abeer_engjbr New Member

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    Hello For All,
    I Have constructed The Ir Tester circuit but it dii not work, the led must be on when recieving the ir signal, but it didn't! what is the reason you think? and is there any other circuits that i can know the power of the IR signal comming from mobile ( as it was my goal from the tester circuit), please advise me for what's best to do.
     
  10. Abeer_engjbr

    Abeer_engjbr New Member

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  11. Abeer_engjbr

    Abeer_engjbr New Member

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    Help

    Hello everyone,

    Once again I'am here trying to get advise from you, hoping that you may be able to help me.

    The IR Repeater circuit I constructe worked, but in only 2 first stages, meaning it catched the ir light and the 555 timer made 38kHz and the output resistor had sequere pulses when sening the signal, but the led didnot flash and the IR leds didnot retransmitte the ir signal...

    May be the reasone is when I took the circuit home to try it in front of the TV , I bought 12 dc voltage battery(TOPCO) it is supply by electricity, any way I have DMM at my place and when I measured the voltage it was 18V without a load and 16.5V when i connect it to the circuit , and I measured the IN pin voltage of the voltage regulator , it was 10.5V , but it must be 12 volt in order for the circuit to work, is it why the IR transmitter didnot work?
    should i connect 6V batteries in series without the Voltage regulator?

    How can i know the polarity of the IR leds? and I used BC549B instead of
    BC549C , and C33725 instead of BC337 , does it make a difference in the circuit or why it did not work probilbly?

    The circuit is in:
    http://english.cxem.net/infrared/ir7.php

    Please help me
     
  12. blueroomelectronics

    blueroomelectronics Well-Known Member

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    Why don't you email the author of the circuit, his email in on the site.
     
  13. audioguru

    audioguru Well-Known Member Most Helpful Member

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    All of your circuit works except the LEDs.
    Maybe the pins on the LEDs are connected backwards.

    The output of the 555 is fine but maybe the pins on the BC337 are connected backwards.
    Here is how they are shown on the datasheet:
     

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  14. Abeer_engjbr

    Abeer_engjbr New Member

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    Thank you all for your time, especaily audioguru.

    I finally completed my graduating project and now I am able to control TV from a good distance using mobile phone as a remote control.
     
  15. Abeer_engjbr

    Abeer_engjbr New Member

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    important

    Hi everyone,
    I need to know why there is two IR Leds in the following circuit ? and if I used only one would it make a difference?
    Thanks.
    The link is:
    http://english.cxem.net/infrared/ir7.php
     
  16. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Two give twice the power output of one, with no extra current required. You could replace it with one, but you would need to recalculate the series resistor, and output would be halved.
     
  17. Abeer_engjbr

    Abeer_engjbr New Member

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    Thanks but I didn't understood your second sentence:
    You could replace it with one, but you would need to recalculate the series resistor, and output would be halved.
    I thought that it is used to increase the coverage distance, isn't it?
    Another thing, does each one send the same pluses at the same time , or the pulses is spreaded for the two of them?

    when there is no signal, i know the input of the ir recevier is high so the BC549c will be on , the collector voltage will be low why? and how is that can anyone explain a littil bit..
     
  18. arhi

    arhi Member

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    If you remove one IR LED, the current trough the other one would be too high, so you need to increase R7 in order to limit current trough IR LED.

    yes, with two led's you have more IR light hence more distance
    yes, they send identical impulses if connected as presented in schematic
     
  19. arhi

    arhi Member

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    The IR Receiver is trigering RESET port of the oscillator via transistor. When the IR Receiver detect signal, it will release oscillator and oscillator will generate signal. when there is no signal, it will hold the oscilator. If that is not clear, check out the data sheet of ne555
     
  20. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    They are in series, so both obviously transmit the same thing at the same time - it's common practice in remote controls to use two LED's.
     
  21. Abeer_engjbr

    Abeer_engjbr New Member

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