Control panel lights and switches

PLMatthews88 Nov 4, 2018

  1. PLMatthews88

    PLMatthews88 New Member

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    Hi everyone -- I am finally getting back to working on my O27 layout and need some advice. I want to build a control panel with indicator LEDs and switches. What voltage and amperage rating should I shop for on LEDs and where is the best source? Do the switches need a certain voltage rating to work properly?
     
  2. trainman-ho

    trainman-ho TrainBoard Member

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    Switches are pretty standard as far as voltage is concerned. Led's on the other hand require specific voltage ranges, and Amperage.....both low. You should talk to someone in the electronics business, either repair, or sales for more precise info!!

    Jim
     
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  3. Hardcoaler

    Hardcoaler TrainBoard Member

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    For a source, I recommend All Elecronics [ https://www.allelectronics.com/ ]. They have a lot of stuff, but not so much as to overwhelm. Prices are good and service is lightning quick.

    Jim is right, that you'll need dropping resistors to reduce current flow to your LEDs. From a 12 VDC power supply, I'm using 3000 Ohm resistors on my green and yellow LEDs and 6200 Ohm resistors on my red LEDs. Resistors are cheap, so you'll want to mess around with various values until you find what looks best to your eyes in your room light. I found the red light to be too penetrating, so lessened its intensity with a higher value resistor.
     
    Last edited: Nov 4, 2018
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  4. PLMatthews88

    PLMatthews88 New Member

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    Thanks! Those are good tips.
     
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  5. traingeekboy

    traingeekboy TrainBoard Member

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    Why not go for the vintage controls? I even thought about using acme controls on my ho layout just because I like panels.
     
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  6. acptulsa

    acptulsa TrainBoard Member

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    You also need to know if you're using DC or AC. How vintage are your 027 trains?

    If you're running this from an AC transformer, I think you'll have to invert. I don't know of any AC LEDs, though I haven't actually looked. A diode may suffice.
     
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  7. Onizukachan

    Onizukachan TrainBoard Member

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    That’s because Red has a much lower forward voltage, thus more lumens for any given voltage, fyi. Red are something like 2v green yellow 2.5 -2.7 and white or blue are 3.2v.
    Hopefully this helps folks plan ahead, or if using a resistor calculator on the web.

    Can always use 4 diodes as a bridge rectifier if working with AC also.
     
  8. Hardcoaler

    Hardcoaler TrainBoard Member

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    That explains it then. Hard as I tried, I couldn't get all three colors to glow at matching intensity using common resistor values, but they're very close.

    Yep, diodes are handy little guys in all sorts of applications.
     
  9. Onizukachan

    Onizukachan TrainBoard Member

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    Resistors in series are cumulative (300 + 66 =366), while resistors in parallel are averaged (100+100+100 = 33).

    Hope that helps someone, I use this to my advantage to create custom values. Especially when I don’t have the desired value in my kit.
     
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  10. SP_fan_1951

    SP_fan_1951 TrainBoard Member

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    That only works for resistors of the same value - the easiest accurate formula is the reciprocal of the sum of the reciprocals 1/(1/R1 + 1/R2 +1/R3 + ... +1/Rn) A quick math check is that the total parallel resistance will always be less than the lowest resistors value. For example a 100 Ohm in parallel with a 50 Ohm has a parallel resistance of 33.33 Ohms.
     
  11. Onizukachan

    Onizukachan TrainBoard Member

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    Good point, I over simplified.
     
  12. trainman-ho

    trainman-ho TrainBoard Member

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    I have a bunch of cheep small Model Railroad power supplies which I set up using a voltmeter to the desired voltage. and then use tape to lock the unit in the proper position for the desired output. I label the unit's voltage with a piece of tape. I started doing this when I needed a power source late one night in a remote location, (No stores) and have been doing it ever since.

    Jim
     

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