wiring up a LED light?

Discussion in 'FAQs' started by Marxed, Nov 14, 2005.

  1. Marxed

    Marxed Member

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    okay, i want to get a nice big bright light in one of my marx... i know i'll most likely get the power from the pickup and ground it to the wheels.... i'll be running on standard lionel track and a 50watt transformer....



    i have a slight idea of how i want to do this.... but can anyone point me in the right direction.... like what type of light to buy??? do they come in diff wattages and stuff or anything? LOL i honestly never bought a LED light before....



    okay... soo basicallly what should i know before i undergo this and what type of light...? also, pointers of how to mount it inside the loco would help!
  2. shaygetz

    shaygetz Active Member

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    I use 3mm LEDs wired with a 1/4 watt 750 ohm resistor on most of my installs. If the headlight jewel is thick enough, I'll use a 2mm unit glued into a hole drilled into the back of the jewel. Other than that I'll post it in the original socket after it has been disconnected from the rest of the locos circuitry.
  3. Marxed

    Marxed Member

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    i'm not wiring it into anything... just stright to the track pickup and grounding to the wheels....


    is the resistor needed to run the light?
  4. 60103

    60103 Pooh Bah

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    LEDS are 1.5 volt devices. I'm not sure what sort of resistor you need to work with the 16 V AC. (is that what Marx uses?) but you definitely need a resistor.
    There are other ways where you wire it in series with the motor and use a set of diodes to drop the current. Again, not sure how it works with AC.
    I think you can also get bright white LEDs.
  5. Marxed

    Marxed Member

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    lol, i honestly dont even know the power stuff off the top of my head... i just know it's the same as lionel type stuff... the transformer i mostly use is actually a lionel one... i just took a peak and its 5-6 volts and it says 90watt... it's one of the ones with 4 connectors on the top, U, A, B, C... and u connect the wires up accordingly for what power levels you want and i have mine on U-A... for 5-6volt....
  6. 60103

    60103 Pooh Bah

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    Better get the magnifying glass out. :thumb: If it's like my Lionel 90 watt, the U-A posts go up to 16 volts.
  7. Marxed

    Marxed Member

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    typo on my behalf, i wrote the numbers into my cell phone and my phone says 16, soo i just missed a key when copying it into here :D

    soo 5-16V
  8. jim currie

    jim currie Active Member

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    you have to convert the AC to DC would recomended a full wave rectifier then off the outputs of the FWR place a capacitor with a resistor in series with it (filters out voltage spikes) then connect the led with a 1.5K ohm resistor in series with it.
  9. Marxed

    Marxed Member

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    full wave rectifier.... sounds like something the aliens use when obducting the people in plasticville :eek:


    i learned the basics of electricity in physics one year but i'm almost clueless to everything you just said
  10. ezdays

    ezdays Out AZ way

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    Jim,

    It's not always necessary to use a rectifier in these cases. The LED in itself is a rectifier and will convert the AC to half-wave DC meaning that the LED will be powered by an oscillating DC pulse half the time. The good thing about this is that it is not polarity sensitive. This is normally good enough at 60 hz to not see any flicker and you can use a slightly higher voltage since the voltage is averaged out, plus most LEDs can withstand short spikes.I've run LEDs right from 110 VAC without difficulty. Yeah, it required a big resistor, but it worked.:eek:

    That being said, I agree, the best way to do it is to use a steady DC voltage. I seem to remember building a regulated DC converter and installing it in a Marx engine for someone from the Gauge a while back, but I think it was to run a sound module.:confused:
  11. Marxed

    Marxed Member

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    how hard is it install all that and whats the price range on everything??
  12. ezdays

    ezdays Out AZ way

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    If you're talking just the LED and a current-limiting resistor, just a few bucks and fairly simple. If you want to add a rectifier and filter, you can add about another five bucks to that, and an hour or two to build and install it, depending on where you have the room in your loco. Adding a regulator will cost another couple of bucks, and require even more room and expertise to build.

    A wide range of cost and time to implement a solution.
  13. yellowlynn

    yellowlynn Member

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    Led


    Jim, That's easy for you to say. If you hook the AC end of the wire to the DC end, would the capacity of the capacitator equal the ohm of the PNS when it is rectified to voltage of 12 to the 3rd power? Then be resisted by .000002k whatevers?

    Lynn
  14. Pete

    Pete Member

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    Only on the second Tuesday of every week, if it occurs during a blue moon.
  15. jim currie

    jim currie Active Member

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    EZ the reason i added the filter is that i've been messing with leds on the rr for the last year and on my immaculately clean :rolleyes: track if i don't use a filter the leds burn out at a alarming rate :oops: . that is on DC but would think that AC would have the same problems.

    Yellowlynn that only happens if you buy your canned B+ from china :p
  16. ezdays

    ezdays Out AZ way

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    Jim,

    I understand your being gun-shy, and as I said, a filter or a rectifier is not necessary, but if you can, or if you find you need to, by all means put one in. Spikes (much higher voltage for real short periods of time) or noise (constant presence of high frequency, smaller spikes) are usually due to the quality of the source voltage (power pack) and the loads put on them. Starting a DC motor can put a heavy load on the power pack causing the voltage to dip, the lower the power rating, the worse this can be. But stopping a motor can put an instantanious negative spike on the power source that can cause problems. The same goes for operating a DC relay or solenoid. All these things can cause problems with electronics and in your case, could be the reason for the LED burnout. There are several ways to protect from this, and you do the minimum that works.:D

    In the electronics that we built over the years, I always put a bunch of .01 mfd caps throughout as filters for these short spikes.
  17. cidchase

    cidchase Active Member

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    We had some discussion a few months ago in which it was revealed (IIRC) that
    most LED's have a very low peak inverse rating (PIV) :( and this could cause
    burnout :curse: if they are used as their own rectifier. So maybe the FWR is a good idea. :)
  18. cidchase

    cidchase Active Member

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    Or this? :)

    Attached Files:

  19. ezdays

    ezdays Out AZ way

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    It's been a very long time since I've looked at the specs on an LED for PIV, but if it is a problem, a reversed-biased diode will work. This is one the the tricks I was talking about to prevent damage due to these negative spikes from relay coils, solenoids and motors being shut down, and in this case, will bypass the LED on the reverse half of the cycle and reduce the stress from the inverse voltage being applied.

    A lot easier and cheaper to implement than a bridge rectifier and filter. But again, I say, do no more than what you need to.
    .
  20. jim currie

    jim currie Active Member

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    EZ the reason i use a full wave is so i can run a flashing yellow led as a beacon on my yard switchers.also at the ungodly price of golden white led's you need to take every precaution.