Question about IR receiver diode !!

Discussion in 'Homework Help' started by LETITROLL, Apr 9, 2014.

  1. LETITROLL

    Thread Starter Member

    Oct 9, 2013
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    Hi every one here .

    I have an IR receiver diode with 3 pins , IN , OUT and GND , i have put a signal on the input using a 5v and a 100 ohm resistor just to see how it works , With my DMM i see a constant 4.6 v on the output without triggering the receiver .

    Is it normal or i should get an output signal only when i transmit IR signal to it ?

    [​IMG]
     
  2. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
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    Yup. However, you need a modulated IR signal...

    What's the part number?
     
  3. LETITROLL

    Thread Starter Member

    Oct 9, 2013
    218
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    Hi tschuck

    Its written on it B146 .

    So if i get an output signal with out sending an IR signal from remote , the receiver is considered bad ?
     
  4. joeyd999

    AAC Fanatic!

    Jun 6, 2011
    2,692
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    Would that be this?
     
  5. LETITROLL

    Thread Starter Member

    Oct 9, 2013
    218
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    The one i got has pin 2 as GND
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,567
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    Is the output 50ma capable?
    Is the output NPN O.C.?
    Max.
     
  7. MrChips

    Moderator

    Oct 2, 2009
    12,449
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    Read the datasheet if it is available.
     
  8. hexreader

    Active Member

    Apr 16, 2011
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    Looks to me like it might be a Sharp GP1UX511QS. If my guess is right, there will be a big "S" on the back of the device.

    The thing that bothers me is that I do not see a raised cross on the window bulge, so maybe I am wrong with the exact device, but it is probably something very similar, if not that exact device.

    The output of a 3-pin IR receiver will be high for no signal and will go low when 38kHz is received.

    Note that steady 38kHz will not take the output low - as tshuck said, the 38kHz must be modulated.
     
    Last edited: Apr 9, 2014
  9. LETITROLL

    Thread Starter Member

    Oct 9, 2013
    218
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    You got it right HEX , it has a big S on the back and also an X on the front covering the IR lens ( if that's the word ) , but i have looked at the pcb where it was soldered and i found that pin 2 is connected to GND unlike the one you found , and also it has 500 uA input current .

    I have checked the signal changes with an oscilloscope , and i get a constant high at the output knowing that am having an input of 5v and current of 50 mA ; And when i press the remote the output signal on the Oscillo becomes disturbed


    So as far as i understand , we have an input for the diode and an output having the same value as the input , and when we send an IR signal , the output signal changes to a signal proportional to the IR frequency and modulation with the same input's amplitude ?? is that how it works ??

    What is the normal output and input currents for these type of diodes ?
    Can a 50 mA burn it ?
     
    Last edited: Apr 9, 2014
  10. hexreader

    Active Member

    Apr 16, 2011
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    Datasheet for the series is here:

    http://www.sharpsme.com/download/gp1ux51qs-epdf
    Yours is the "511" version I believe.

    If by "pin 2" you mean the middle pin, then the datasheet shows this to be ground.

    There is no "input" in the signal sense, just 5V supply.

    Calling the device a diode is very confusing, and yes, I know that is what the datasheet says. It is actually a sophisticated integrated circuit that happens to contain a diode within it as the receiving device.

    The output will be an inverted version of the modulation signal from the transmitting device (TV remote?). Not an exact representation of the send signal though. The receiving and de-modulating circuitry distorts the signal a little.

    No. IR frequency will be a fixed 38kHz (approx). The 3-pin receiver gives a digital output, not analogue.

    See this site for a good explanation of domestic IR remote basics:

    http://www.sbprojects.com/knowledge/ir/index.php
    Note that the IR receiver shown on this site has a different pin-out to yours
     
    Last edited: Apr 10, 2014
  11. hexreader

    Active Member

    Apr 16, 2011
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    Just measured the current to my 3-pin IR receiver with 5V supply...

    The receiver draws 0.5 mA with no signal.

    The receiver draws 0.6 mA when receiving.

    This is with the 3-pin receiver output not connected to anything.
     
  12. LETITROLL

    Thread Starter Member

    Oct 9, 2013
    218
    2
    Ok thanks hexreader .

    Actually the IR receiver am using is part of a design that amplifies the output signal using PNP transistor , the amplifier output ( test point ) should go to a debounce circuit composed of two NOR gates , but when i send an IR signal , test point shows only 0.5 v !! witch can't be used in the NOR gate , please check the circuit bellow and correct me if am wrong .
     
  13. hexreader

    Active Member

    Apr 16, 2011
    250
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    Check the datasheet. You are missing a 47uF capacitor across the 3-pin receiver supply rails.

    I assume that you use a 5V DC supply?

    .... but I doubt that this is the cause of your problem - will dig deeper...

    Update: Have tried your circuit... All the transistor seems to do is to invert the signal. I do not know why you want to invert the signal.

    ... but it works as I would expect...

    Are you measuring the test point with an oscilloscope (good) or a multimeter (bad) ?


    ... and why do you want to debounce the signal? seems like a strange thing to do. Maybe you could tell us the bigger picture of what your project is about.
     
    Last edited: Apr 11, 2014
  14. LETITROLL

    Thread Starter Member

    Oct 9, 2013
    218
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    Am using a 5v supply ( using PC's USB port) .
    The debounce is to have no flickering at the output LED when the IR signal is sent .

    The thing i don't understand is why am measuring only 0.5 v with DMM , but with OSC i see something like a pulse at the entry of the NOR gate , i guess that's not sufficient for the gate to work or ......

    Here is the rest of the circuit :
     
    Last edited: Apr 11, 2014
  15. hexreader

    Active Member

    Apr 16, 2011
    250
    82
    Using a DMM to measure pulses is near to useless - don't do it.

    Hopefully your Oscilloscope shows pulses going approximately between +5V and 0V - what levels are you seeing on your oscilloscope?

    The rest of the circuit "sort of" works, but seems like a complicated way to do not much. - but the LED goes off in response to TV remote signals, if I adjust the potentiometer carefully. I found that I needed to change C2 from 47nF to 4.7uF electrolytic to make the circuit do anything sensible.
     
    Last edited: Apr 11, 2014
  16. LETITROLL

    Thread Starter Member

    Oct 9, 2013
    218
    2
    Thanks for taking the time to do the tests , actually the Led should be turned off by default , it lights up only when you press the remote .
     
  17. hexreader

    Active Member

    Apr 16, 2011
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    There are four NOR gates in the IC package, so you can use the fourth one to invert the LED output.

    Alternatively put the LED between +5V supply and pin 10 of the 74LS28. Be sure to get LED orientation correct.
     
  18. LETITROLL

    Thread Starter Member

    Oct 9, 2013
    218
    2
    Ok here is my point of view ;Lets suppose we have the led turned on by default according to the designs i have previously uploaded .

    That means we got high at pin 10 , low on pin 4 , thus high on pin 1 as a result of 2 & 3 being low .

    But my exercise demands that i should have the led turned off by default with the actual circuit configuration without changing anything.

    I know there is something tricky there ...
     
  19. hexreader

    Active Member

    Apr 16, 2011
    250
    82
    OK - I think I get it now....

    VR1 needs to be adjusted so that the inputs pins 5 and 6 are not quite driven high enough to show as a logic 1.

    So yes, with VR1 adjusted just right - the circuit will give a normally-off LED with no signal, then the LED lights when a signal is detected.

    I agree with the "tricky" statement. This is an unusual way to use a logic gate. It is using the gate almost as if it were a transistor.

    .... but, I have to admit it works !
     
    Last edited: Apr 11, 2014
    LETITROLL likes this.
  20. LETITROLL

    Thread Starter Member

    Oct 9, 2013
    218
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    Ok thanks for the assistance .
     
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