Large Scale Central

DC Power for illumination?

Problem Solving
#1

CAVEAT: I AM NO ELECTRICIAN. Ok, don’t laugh, but I have a dumb question. I’ve always connected my lights for illumination (buildings, lamp posts, accessories) to my AC terminal of my powerpack. However, I keep reading that LEDs and other illumination devices can be run off DC/track power? Is this so? How is that possible? I might sound stupid, but every time I throttle up or down on the DC power, wouldn’t the lights increase and decrease in intensity? Am I missing something?

I’ve been researching arc-welding simulating LEDs, does anyone have experience making an arc-welding light simulation for their layout?

Example of an arc-welding simulation I’d like to install

#2

Some paks have a fixed DC terminal for accessories.

I have always liked to use a separate pak to power the building lights. I hook it to the track

terminal so I can change/control the amount of light overall.

Rick

#3

Yes, the light intensity will vary with track voltage, if you use dropping resistors. If you use a control circuit, like a CL2, then the LEDs would not vary much, but they will go out when you reduce the track power to below a certain voltage.

It would be best to use a separate supply altogether. If its an AC supply, then you can make DC power from it with a simple bridge rectifier. LEDs only lite when the power is flowing in one direction. They are polarity sensitive.

#4

Perhaps the suggestion for track powering accessories with a DC train power supply was that of or from a DCC equipped railroad… In this circumstance Voltage on the rails should be realized as a constant voltage, alas not all power sources can hold the line without experiencing voltage degradation under load. Low voltage lighting stuff and similar ilk with some form of voltage dropping gadget inline will not typically be effected by slightly varying voltages realized of sub-standard or anemic power supplies under load.

Michael

#5

I like my lights on at night, even though I’m not running. Like to look out and see the lit up town and landscape lights. I use the Malibu units and wire. THey are AC power. It also powers the lights in my buildings.

#6

Jay:

There are some ready-made welder effect LEDs available. Here’s one - Easy Welding Effect Kit

#7

The cheapest and easiest way to do a “welder” is to take advantage of “relay chatter.” This is what I did when I made a module for the Del Oro Pacific.

Initially, the module used a wheel with brass contacts driven by a clock motor to alternately make/break a contact so as to form an “oscillator” to trigger the relay. This mechanical assembly was later replaced by a 555 timing chip.

Simply wire a dpdt relay so that the one leg of the coil goes though one of the normally closed contacts. Wire your LED through the other normally closed contact. When power is applied…, the relay will toggle but in doing so breaks its own connection so that it resets itself, so that it toggles again but in doing so breaks its own connection so that it resets itself, etc. etc. etc.

Meanwhile, the other contact is continually making and breaking causing the LED to flash. As an unexpected benefit (serendipity), you can physically hear the relay chatter and when it would resonate in the wooden framework on the Del Oro Pacific module, it sounds like someone welding.

#8

Todd, got a schematic? TIA. Also, even though an LED only lights when current flows in the proper direction, you can run them with AC. They’ll be off half the time, but at 60 times a second our eyes don’t see the flicker.

I also use Malibu light systems for my RR buildings and other lighting, but have replaced the 7 watt and later 4 watt bulbs with specialized LEDs that fit in the Malibu fixtures.

#9

I am using ElCheepo Christmas lights on my Malibu. The bulbs are 3 volt bulbs, so I have to wire enough in series so that I put 3 volts or less to the bulbs. I prefer running them at about 2 volts. That gives a nice orange glow, like lantern light, and they should last a very long time that way. But since I bought strings of them at yard sales for like 50 cents a string, and even salvaged a few from the trash, I don’t need to worry if a bulb or two burns out. I have a nice supply laid in.

#10

Jay- I am undoubtedly the least qualified person to answer your question, but I will anyway. You could power your LED’s from a separate DC transformer- not the one you are powering your train with. The easiest way I found was to use an old 12 Volt DC “wall wart” power supply (like the kind you find on an old cordless phone charger or answering machine). Cut off the end with the jack on it and attach the positive wire to a resistor (I use radio shack 480 ohm), then from resistor to long leg of LED, from short leg of LED back to negative wire. The more lights you are powering, the more milliamps your 12 volt wall wart will need.

I use the LED arc welder from miniatronics. It comes ready to run on 12 volts, so no resistor is needed.

Hope this helps.

-Kevin.

#11

i understand electronics as good, as a cow understands christmas.

but i found some working solutions.

a powerpack from an old computer gives you from 3 to 24 volt DC. (depends which contacts of the plug you connect to)

a telephone transformer gives you 8 or 9 volt.

by using this kind of junk, the transformer/regulator for the trains can give all its juice to the trains, and one can light independently.

#12

Dick Friedman said:

Todd, got a schematic? TIA.

The relay chatter is simply wired as I noted. But the trick is to have this cycle, rather than run continuously. As I noted, I initially did this using a “clock motor” with contacts to determine the on/off times.

This is the electronic equivelent circuit that I developed to power Gustav and makes him alternately push ice into a reefer (as featured in Garden Railways Magazine). IC2 is an oscillator that tells Gustav when to “jab” and when to stop. R2 and R3 form the duty cycle. The IC charges through R2 and R3, then discharges through R3. So if R2 is small (but at least 1K) and R3 is large, its near a 50:50 on/off and the value of R3 and the cap determine the oscillator period. If you want a long pause and a short “arc time,” you would increase the value of R2 to further increase the charge time relative to the discharge time.

IC1 is the “flash rate” for the LED (or rate at which Gustav jabs at the ice). I used a solonoid to make Gustav jab, but in your case you would just use a superbright LED instead of the solonoid. Actually, you wouldn’t even need the relay and the LED could directly take its place if you add a series resistor to limit its current.

The alternative is to just use IC2 and connect the relay to pin 3 and ground as is shown for IC1. In this case use a dpdt relay and wire pin 3 through one of the normally closed contacts so that when it starts to activate, it breaks its own circuit causing the relay chatter.

BUT, the chattering relay makes a lot of EMF and can cause fits for the 555 chip unless various precautions/measures are employed.

(http://largescalecentral.com/public/album_photo/34/dd/01/1da58_0e16.jpg?c=07ad)

#13

Jay

You can consider buying a complete kit. Look at http://www.modeltrainsoftware.com/welding.html

For $9.00 plus shipping from CO, the kit will work on 5 to 19 volts AC-DC-DCC.

It’s a very simple pre-assembled led kit with 3 flashing leds, a built-in resistor and a bridge rectifier.

I have sold many to my HO customers.