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Turns on LED upon receiving IR signal

Discussion in 'LEDs and Optoelectronics' started by DutCampos, Jul 2, 2014.

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  1. DutCampos

    DutCampos

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    Jul 2, 2014
    Hi everyone, I'm working on what I think is a fairly simple project. However, I have no previous experience with electronics, so help would be greatly appreciated.

    I have to build two pairs of circuits: an IR transmitter and an IR receiver for each (let's call them pair A and pair B). The IR receiver needs to receive a signal from the transmitter and, upon receiving it, turn on a visible light LED (color doesn't really matter).

    The two catches are: 1) The pairs need to be "unique", meaning that Receiver A can't light up upon receivipng a signal from transmitter B (I think this means I need to modulate the transmitter's carrier frequency). And 2) I need them to be as small as I can possibly make it, especially the receiver.

    Here are some ideas, from what I've read:

    Feel free to disregard all of this if it's stupid or if you have a better idea!!

    a) The receiver would use something like this (https://www.sparkfun.com/datasheets/Sensors/Infrared/tsop382.pdf) of two different carrier frequencies. I would use that to light up a regular LED with a small button-cell battery.
    b) I could use this (https://www.sparkfun.com/datasheets/Components/SMD/DS1077.pdf) to modulate the carrier frequency on the transmitter, maybe?
    c) Build the receiver circuit on this protoboard (https://www.sparkfun.com/products/8886)

    Ask me if you have any questions and thank you for your help!
     
  2. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Both IR receivers will respond to the Transmitter even if you are modulating them. It's what you do with the modulation that is important. they use a 38KHz carrier that you modulate. You need to modulate them differently and then process that modulation to find out which one is which. I don't think you will be able to have them on together as they might interfere with each other.
    Adam
     
    Gryd3 likes this.
  3. Gryd3

    Gryd3

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    Jun 25, 2014
    I can confirm messing with numerous people and things with an old TV remote.
    I would hold a button down on it and the other devices would fail to receive the commands from the matching remote XD
     
  4. Arouse1973

    Arouse1973 Adam

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    :)
     
  5. DutCampos

    DutCampos

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    Jul 2, 2014
    Two transmitter would hardly ever be in the same vicinity as one another, but the receivers would.
    For context, the transmitters would be attached to doors on different corridors and the receivers would be attached to keys (all keys on the same on the same keychain).

    Does that change things?
     
  6. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Oh ok.
     
  7. Gryd3

    Gryd3

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    Jun 25, 2014
    That sounds bad-a**... am I correct in assuming you are creating a key that lights up in response to which door it is meant to open?
     
  8. DutCampos

    DutCampos

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    Jul 2, 2014
    Hahaha yes, you are!
     
  9. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    How about using those coloured plastic rings that you slide over the grip part of the key? You can get them in about ten different colours. Then just stick a piece of coloured plastic, or some paint, on the door near the lock. Then you just match the colour on the key with the colour on the door.

    http://www.amazon.com/Custom-Accessories-44449-Key-Identifiers/dp/B004PAHTQY

    If you really want an electronic solution, I think it might be workable. You would need a very small receiver. Have a look at http://www.digikey.com/product-search/en?FV=fff4001e,fff803b0&stock=1&quantity=1&pageSize=250

    I suggest you use the same carrier frequency for all keys, but different data, just like different commands on an infra-red remote control. In fact you could even use IR remote controls as your transmitters! Then of course you would need something to decode the commands - a small PIC or AVR microcontroller would be fine.

    Even using a CR2032, current consumption of the IR receiver would be an issue; could be mitigated by having the microcontroller wake up once or twice per second and power up the receiver long enough to detect a signal if there is one.

    The smallest receivers I could find on Digikey are:
    Vishay TSOP75456W: http://www.digikey.com/product-detail/en/TSOP75438WTR/TSOP75438WCT-ND/4494443 6.8x3.0x2.35 mm
    Rohm RPMS1381-H19: http://www.digikey.com/product-detail/en/RPMS1381-H19E4A/RPMS1381-H19E4ACT-ND/3769161 4.4x2.5x2.5 mm

    Ultrasonic might be a better option if you can find a very compact receiver. This would be less directional and could use less current.
     
  10. Gryd3

    Gryd3

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    Jun 25, 2014
  11. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    I don't think induction would be practical because of the distance involved. Yes it might be a practical way to transmit a signal, but not enough power to light an LED.
     
  12. Gryd3

    Gryd3

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    Jun 25, 2014
    I don't think a distance requirement was ever discussed. If it only needs to be in very close proximity it would work and would not require any batteries in the keys.. I'd gladly wave my keychain in front of a deadbolt or handle to see which key lit up ;)

    The link I posted above powered 3 SMD White LEDs within a custom-made titanium ring with an 80V p-p Inductor source
     
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