Any way to use the KATO pass car bulb sets w/ DCC?

[OldEastRR]

I can't believe its 22v either but here's what I have done:

First, I have one of the old-time multimeters a Radio Shack job from the 70s-80s, with a swinging needle. Maybe that’s not the right kind of meter to use. I have a digital one somewhere if I can dig it up if you think that’s the problem.

OK, method one, using the AC voltage setting: + to a rail, – to the GROUND post = 22v. 

Method two, using the DC setting: + to one rail, – to GROUND = 10v; +to other rail, –to GROUND = 10v.    I think  I’m supposed to average them out? You tell me. 
Anything else needed to know about getting a voltage reading?

Yes, the KATO LEDs light up the train like a Chicago El train interior. Maybe I could cut that intensity down with a resistor, and use yellow filters to get incandescent effect. The little plastic filters that come with the LEDs do not produce results I'm satisfied with. Also it looks like running 7v through the bulbs keeps them from overheating but they are too weak to light the entire car. But I assume going to 8-9v would turn them into heat blasters. However putting 2 7v bulbs in one car w/ 2 resitors should give me more even interior light and divide the heat among 4 units, right?
BTW, if you can figure out the voltage of my track like this -- I get a 7v reading when a bulb and a 330 ohm resistor (but it gets real hot, I think it's low wattage) are hooked up to the track power -- please do.

[jdcolombo]

Digitrax says that you can use a multimeter to measure track voltage the second way you did it, by adding together the two readings.  That is, use a multimeter in DC Volts mode, and attach the positive lead to one rail, and the negative lead to a ground on the command station.  Take the reading.  Yours is 10v.  Do the same for the other rail.  Your reading was 10v.  ADD THE TWO TOGETHER (don't "average" them), and you have the track voltage, or in your case, 20v.  One caution: before you take your readings, select DCC address "00" (two zeros) and make sure the throttle is at zero.  This is necessary to make sure that the command station is not overlaying the DCC voltage with a DC output to run a DC-only engine. 

See http://www.digitrax.com/tsd/KB909/track-voltage-measurement-on-dcc-layouts-with-dire/

Assuming you've done this correctly, you have 20v to the track.  This is not impossible.  A Digitrax Chief will output 20v to the rails on the "O" scale setting.   However, that's not what a Zephyr is SUPPOSED to put out to the track - it's SUPPOSED to put out about 12.8v.  I think the output voltage of the Zephyr is highly dependent on the power supply you are using for it.  What kind of power supply do you have attached to the Zephyr and what is the power supply's voltage output?  If you are feeding it 25v, then yes, you could be getting 20v to the track, and you are also way over-stressing the internal Zephyr components.  The recommended power supply for the Zephyr is the Digitrax PS314, which outputs 13.8v DC.  This in turn should result in about 12.6v to the track.

John C.

 

[OldEastRR]

Going back and doing everything from the beginning, I have straightened out my erroneous reading and the DCC power to the track is 12v. So that's the number I need to use for figuring resistors to step down the lightbulb power.
Operator error. 

[jdcolombo]

Well, then it's easy.  If you want to run your bulbs at 7 volts, then you want to drop 5v at, let's say, 45ma.   R=V/I.  5/.045 = 111, so a 110-ohm resistor ought to do it.  In terms of wattage rating, 45ma x 5v = 225mw.  A 1/4 watt resistor probably would work, but just to be on the safe side, I'd use a 1/2watt, 110 ohm resistor, just in case the bulb is pulling more than 45ma.

Happy Ohms-law-ing.

John C.

[OldEastRR]

How big is a 1/2W and a 1W resistor? Are we talking fat barrels or things about as thick as a pencil?

[nickelplate759]

I found a picture showing a 470 Ohm 1/2 watt resistor at 0.8 cm - about 1/3 of an inch - long, and maybe 2 mm in diameter.

[peteski]

How big is a 1/2W and a 1W resistor? Are we talking fat barrels or things about as thick as a pencil?

See http://www.resistorguide.com/resistor-sizes-and-packages/

Yes, those are metric dimensions - you have to convert them to inches yourself. 

[OldEastRR]

Used to have a metric ruler ... 2.54 cm = 1 inch?

[peteski]

Used to have a metric ruler ... 2.54 cm = 1 inch?

The answer is here

[mmagliaro]

A 1/2 watt resistor isn't too bad.  You can probably find somewhere to squeeze that in.
A 1 W  is getting pretty onerous in size to hide.  Go with the 1/2 W

If you really have trouble with space, you can buy two 1/4 watt and put them in PARALLEL.  That way, you might be able to find room for two smaller physical objects.   Since they are in parallel, they have to each be
double the resistance you want.  If you want 100 ohms, you need two 200-ohm resistors in parallel, like this:

Here's an ugly drawing I made in 30 seconds...



(and you probably won't find 200 ohm, so go with something close like 220 or 180).

[OldEastRR]

My experiments go on. My old resistors were those cylindrical carbon-plastic ones. I got some carbon film type, like little sausages. Ceramic covering? 1/2 watt but these guys still get very warm once running. Hot enough not to be able to hold them. What temp does plastic deform and melt?
However, I wired two 150-ohm ones in series and I get a decently bright light and each resistor just gets warm. So I think I'll go that way. the 1/2 w aren't hugely big, they should easily fit into a compartment or center aisle.
Since the KATO cars have two conducting strips running the length of the car it brings up the possibility of different brightness bulb in separate parts of the car. For the UP dome diner, there could be a bulb for the main dining area, another somewhat brighter for projecting into the dome, and a LED for the kitchen area, looking like bright fluorescent lamps. Each one connected with its resistors separately to the strips.
There have been very few articles or sources about lighting cars, especially in N scale, so this is a fun area to explore. Not very many modelers do car lighting, so limited appeal for mag articles.

[mmagliaro]

Are you sure you wired those two 150-ohm resistors in series and not in parallel?   If they are in series, there is no reason for them to get any less warm, and you would effectively have made a 300 ohm resistor, which would be too dim according to your previous posts.    Two 150-ohm 1/2-watt in parallel effectively makes a 75 ohm 1-watt capacity resistor, with the heat dissipation spread out over two devices.  I am guessing this is what you must have done.  And it makes perfect sense to do it this way to distribute the heat.

[peteski]

Are you sure you wired those two 150-ohm resistors in series and not in parallel?   If they are in series, there is no reason for them to get any less warm, and you would effectively have made a 300 ohm resistor, which would be too dim according to your previous posts.

I'm thinking just the opposite:  AL did wire them in series so now the cuttent in tha circuit is much lower and much less power (heat) is dissipated. He is happy with the dimmer light.

What I don't get is that the dim incandescent bulbs give out orange glow - similar to light from a gas lamp or an oil lamp's flame. That would look realistic in some old-timer passenger car form early 20th Century, not more modern car, which probably uses fluorescent tubes or regular incandescent bulbs.

[mmagliaro]

Oh, forgive me.  I was using info he has sent me in a PM that wasn't here, where he mentioned that
270 ohm made the light too dim for his taste.  So I concluded that if 270 was too dim, then 300 would surely be too dim,
so they can't be in series. 

[OldEastRR]

Hmmm.. maybe Einsteinian laws don't apply to my space. For I have two 150 ohm resistors, fastened together in the middle,with one wire out the end of one and the other wire out the end of the other, hooked to the 12VAC from the Zephyr track power and to the KATO bulb, and my multimeter reads 7.75 volts. To recap: current comes through one pickup, goes into one resistor, then the other, then the bulb, one after another, then back to the other pick=up. And tho both resistors feel noticeably warm, they are not "ouch!" hot as a single 330 or 270 ohm ones gets.
And 7.75-8V through a 12V bulb doesn't look like whaleoil lampglow. At least not to me. It's bright enough but has a yellowish tinge to it. LEDs can't match that no matter what filters are added, because they emit different wavelengths than bulbs.
Yes, I'm a crazy guy living in a universe with different physical laws (apparently), so I just keep experimenting. But this hookup gives me what I need, and I can snake to resistors through the car interior out of sight. I just drill a hole through the floor where it runs over the pickup strip and drop the resistor end of the line down through and in contact with the strip. I think I'd be happiest with solder connections everywhere, but we'll see.
And in an incredible stroke of luck I have one of the few remaining open Radio Shacks in my small town, and everything is 50% off close out price, and they have the resistors I need!
Luckily none of this project has anything to do with DCC or the light sets would probably melt and blow up.