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Extending IR receiver

Discussion in 'General Electronics Discussion' started by Mustwin351, Oct 18, 2014.

  1. Mustwin351

    Mustwin351

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    Apr 10, 2013
    I have a dimmer that is controlled by an infrared remote. I would like to unsolder the IR diode and extend it so it can reach another location approximately 25' away. I have cat 5 cable to do this but am unsure how to wire my 3 leads on my IR diode.

    Do I use a single twisted pair for ground and +5V power or instead should the twisted pair be between signal and ground?

    Thanks.
     
  2. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Are you talking about moving the IR receiver out of the dimmer and putting it somewhere else so you can control it using the remote control in another room?

    There are several factors involved here. The first one is safety. It's very likely that the dimmer circuitry is powered from the mains (line) supply using a capacitor-fed power supply, so all of the dimmer circuitry, including the IR receiver module, is directly connected to the line. It may be half-live or potentially fully live depending on the design of the power supply. In either case it is not safe to connect any external wiring or components to that circuitry because of the shock and fire hazards. The only way this wouldn't apply is if you KNOW that the dimmer's internal circuitry is fully isolated (even then, bringing wires out of the circuit may be illegal and/or dangerous), or explictly earthed.

    Second, the signal coming from an IR receiver/detector module is not designed to be sent over long distances, and could be corrupted by electrical or magnetic interference from wall wiring, appliances, etc. So it might not be reliable.

    I suggest you get an infra-red repeater. These have an IR receiver and radio transmitter at one end, and a radio receiver and IR transmitter at the other end, which you point at your dimmer.
     
    Harald Kapp likes this.
  3. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    The wires would have to go from the IR-diode to the same two points where the IR diode previously sat on the PCB. This doesn't necessarily have to be ground , +5V or whatever.

    I strongly recommend not to do as you propose!
    The potential on these wires can possible be lethal as a typical dimmer is not isolated from mains. Extending wires from the dimmer's internal circuit to any length poses the risk of making mains potential accessible without any protection. CAT 5 cable will not even provide a clues to the unsuspecting that there may be high voltages involved and the insulation is not meant to rpvide protection against mains voltages.
    A better way would be to put the dimmer in a safe enclosure and use standard mains-rated components (cable, plug, socket etc.) to put the dimmer within reach of the IR sender and have it control the mains load via suitable installation material.
     
  4. Mustwin351

    Mustwin351

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    Apr 10, 2013
    Sorry guys I left out one critical detail. The dimmer is powered by 12v. It's all low voltage.


    I've seen long "add on" ir modules (like the one for my cable box that are 25' long) so in theory it's possible. Not sure if it's shielded or how they go that distance. I'm sure using the corrected combination for the twisted pair is important but have been unable to google for info with much success.
     
  5. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    The purpose of twisted pairs is to keep the induced noise common mode. You will get some cancelation because of the twists but anything that get through will be seen as common mode noise and should be dealt with by the receiver. Shield just help to limit the amount of induced noise.
    Adam
     
  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    What's the manufacturer's name and the model number of the dimmer?
     
  7. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Oh, it's a LED dimmer! That should be safe enough.

    You should be able to connect a second IR receiver device in parallel with the first, so you can control the dimmer from either location. If you want to do that, find out the part number of the receiver unit, so we can choose a suitable device to connect in parallel with it.

    Re the usage of CAT5 cable. Ideally all three wires should be twisted together. I guess you could pull the insulation off, throw away five of the wires, retwist the remaining three, and slide the insulation back on, but for an eight metre cable, that's a lot of hassle.

    Also, I think the cable should probably be screened, although that would increase the capacitance.

    You'll need a decoupling capacitor directly across power and 0V pins of the IR receiver device at the end of the cable.

    You might have to reduce the pullup resistor on the data signal on the dimmer board to help overcome cable capacitance. The signal line is open-collector with medium impedance. But it's a pretty slow signal, so capacitance may not be a problem.

    That's all I can suggest.
     
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