Save those power packs!

Discussion in 'FAQs' started by kf4jqd, Jun 12, 2004.

  1. kf4jqd

    kf4jqd Active Member

    Here's an idea:

    If your cordless phone dies, save those power packs! You can power LED's and low current lamps with them. I use an old notebook computer power pack to power ALL my lights!

  2. petey

    petey Member

    What an interesting idea. I presume you are alluding to the battery charging circuitry. I have thought, many times, that unused converters, with sufficient output, would be useful for these pourposes.
  3. kf4jqd

    kf4jqd Active Member


    You are right about the charger. I have an Nscale layout in the bedroom. I use an older charger to power a couple LED signal lights. Works fine. Don't for get the dropping resistor if you use LED's!

  4. jwmurrayjr

    jwmurrayjr Member

    Circuitron mentions that as many as 30 Tortoise switch machines can be powered by a single 9-12 volt 500ma "wall wart".

    Who knew? :thumb:
  5. Fred_M

    Fred_M Guest

    Been using wall warts for years. They can power lights, switch machines, even locos with a throttle attached to them. Fred
  6. Pitchwife

    Pitchwife Dreamer

    When I cleaned out my electronic repair shop and scavenged the motors, gears LEDs and whatnot from anything left over, I had a special box just for the wall warts. I knew that they would come in handy someday. Just plug them all into a switched outlet strip so you can be sure that they are all turned off at the end of a session.
  7. McFortner

    McFortner Member

    Just be careful. My soon to die notebook has a power pack that puts out
    19.5 Volts!!!! :(

  8. kf4jqd

    kf4jqd Active Member


    That's what a voltage dropping resistor is for! :p

  9. hocaboose

    hocaboose New Member

    the output voltage is usually cast into the body of the wall wart. Been using various ones for years as they surely beat the price of 110 to 12v step down xfmrs.

  10. Fred_M

    Fred_M Guest

    Just build a simple and cheap voltage regulator from a LM317Tand scaps and even that 19.5V can run LEDs without a dropping resistor. One LM317T will run about 50 LEDs. You can also use resistors with LEDs. Here's a great site Shamus found ,The resistor drops the voltage to what the LED nee3d to survive Andy, most Leds are 3.3 v and 20 ma so use that figure when you don't know. Fred
  11. Dave Farquhar

    Dave Farquhar Member

    An ATX power supply can be a useful source of power too. On the big 18-pin plug, if you ground the green wire to the black wire, it'll power up, and then you can make use of its 3.3 volt, 5 volt, and 12 volt connections, or mix them to get 1.7 volts, 8.7 volts, or 7 volts. You can get the pinout at, among other places. Just be careful--Dell power supplies are different, even though they look ATX.

    200-watt ATX power supplies that are no longer useful for computers are dirt, dirt cheap, and *plenty* useful for stuff like this.
  12. sumpter250

    sumpter250 multiscale modelbuilder

    Just one word of caution here. 200 Watt......A computer power supply can deliver 40 AMPS of current, at 5 VOLTS (5V X 40A=200 W)
    If you get a wedding/class ring across that 5V will get hot enough to bar-b-que the ring finger. :eek: It's not the voltage, I've been nailed by 14,000 volts, it's the current through the body that maims, and kills.
  13. RailRon

    RailRon Active Member

    Pete is right here - take care with high current outputs! Always install some sort of a current limiter - this can be a elaborate electronic contraption or even a simple fuse.

    It is mainly the current (Amperes) which is responsible for heating up a wire. If you install bus connections under the layout which carry high currents, be sure to use very heavy gauge wire. In case of a short somewhere thin wires quickly are heating up... :eek: :eek: You don't want your house go up in flames, do you?

    BTW- the same holds true for trickle charged car batteries as a power source. These things can deliver currents up to more than 200 Amperes. (That's a normal peak current when you are starting your car.)
    Long time ago, when I looked for more power for a slot racing layout, I installed such a power source. Accidentally I touched both poles with a small screwdriver - the metal was vaporized instantly and I had quite nasty burns on my fingers! :oops: (Still have the scars.) That's why for my model RR room, car batteries are a definite no-no!

  14. Jodam

    Jodam Member

    All controllers should be fused with quick blo fuses. I fuse the track side, at 25% higher than the expected required max. Resetable circuit breakers are also a good idea.
    Even 3 Amps will weld Rings and other jewelry to the tracks. I've been caught by accidentaly shorting a large Cap with my wedding ring.
  15. Fred_M

    Fred_M Guest

    Yep, putting on a wedding ring causes enough pain and scarring with shorting it out and branding you too. An old trick from the 50's was to use a car headlight as a current limiter in series with high amp power supplies. Works great and is cheap. Also it's easy to know when you have a short as it lights up. Fred
  16. RailRon

    RailRon Active Member

    On my slot car circuit, car headlights were used with good success by me, too. Afterwards... (see above) :D :D :D

    Frankly, I had forgotten this simple trick. Thanks for reminding me, Fred!

  17. kf4jqd

    kf4jqd Active Member

    Can You beat this?

    I have seen all kinds of power supplies on here. That is good! However, here's my Astron RS-35A power supply. The specs on are the following: 13.8vdc and 35amps! It powers my Kenwood TS440 and TM721A radios, Palomar meter, and a test lug on the workbend. And yes, EVERYTHING is fused!


    Attached Files:

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