LED passenger car lighting with DCC

[MisterBeasley]

I'm going to be wiring up some interior lights in passenger cars using LEDs. Since the D stands for Diode, I plan to just wire the LEDs in series with a resistor and put them across the track voltage. The DCC voltage is alternating, although not true AC, so the LEDs should work on half the cycle and not on the other.

Is there anything wrong with doing this, or would I be better off putting in a diode bridge so that I get full-wave rather than half-wave rectification? If I did that, would it then be worthwhile to put in a capacitor to help ride over short power dropouts?

[cacole]

Just an LED and resistor will work as long as you get the correct value resistor; however, your LED will be receiving only 1/2 of the DCC square-wave AC waveform so it will be dim unless you risk using a lesser value resistor.

You'll probably find dirty wheel flickering an annoyance, so a full-wave bridge rectifier/capacitor/resistor network would be better. A small bridge rectifier such as the one sold by All Electronics (http://www.allelectronics.com) at catalog number FWB-15, a 1.5 Amp 400 PIV, priced at 2 for $1.00, together with an electrolytic capacitor of the highest mfd rating you have room for, would give you both halves of the waveform and filter out dirty wheel glitches. The value of the required resistor will depend on the capacitor, so you'll need to measure the fully charged capacitor and then calculate your resistance.

[Don Gibson]

Use a BRIDGE RECTIFIER and VOLTAGE REGULATOR, then a RESISTOR to give you 2 - 2.1 volts .

The rectifier gives you constant DC, the regulator to give you constant brightness, the resistor limits current; and add GOLD Capacitor if you want to reduce flickering.

LED's need DC and current limiting. OR you can buy the whole package from http://www.richmondcontrols.com/ - then all you have to do is get the power from the wheels into the car. Walthers' Terminal Warehouse is having a sale on insulatedPassenger trucks that can be used to pickup track voltage

[nfmisso]

QUOTE: Originally posted by Don Gibson

Use a BRIDGE RECTIFIER and VOLTAGE REGULATOR, then a RESISTOR to give you 2 - 2.1 volts .

and finally the large capacitor. The resistor will slow down the charge rate of the capacitor so that you DCC system does not see huge in rush currents.

From All Electronics, link above, the components will set you back $2 or so if you buy in bulk; plus the cost of the LEDs (and electrical pickups)

[AntonioFP45]

I want to use LEDs to light up my Rivorossi streamlined cars, especially since the "blue-whites" more closely resemble flourescent lighting.

A friend of mine pointed out to me that LEDs are "point source" lights. I saw a photo of a modeler who installed LEDs inside of his RDC. Looked nice, but the lighting was barely visible. I don't know the website but I downloaded the two photos.

A little idea I'm going to try.

To help distribute lighting a little better, I went to Hobby Town and purchased a "Chrome Sticker" in the RC Airplance section. It's a 1 foot x 4 inch, peel and stick decal that looks like a mirror!

I plan on cutting the sticker into 2" wide strips and applying them onto the interior ceilings of my passenger cars to help better distribute the LED lighting. With the mirror image, hopefully it will give the effect of "twice the number" of LEDs.

[NZRMac]

QUOTE: Originally posted by AntonioFP45

I plan on cutting the sticker into 2" wide strips and applying them onto the interior ceilings of my passenger cars to help better distribute the LED lighting. With the mirror image, hopefully it will give the effect of "twice the number" of LEDs.

And also stop the light shining through the roof, My bachmann cars have that problem.

Ken.

[Don Gibson]

tampico tony:

Nothing wrong with you 'mirror' strips, but some ALCOA aluminium foil can also be cut with scissors and glue'd to the roof.

TRY NOT TO GET SUPER BRITE LEDs - using more is better - to eliminate luminant 'hot' spots. Train car lights are not blue. Only the glass is - (polarized).

[Budliner]

While voltage regulators have some acceptance in the railroad modelling community, they are a very poor solution to the problem

[Budliner]

Voltage regulators have a high "voltage loss" and high "drop-out" voltage. This means that the input voltage has to be higher than the voltage you want out the other end, and at least 1.25 volts is lost in the regulator. This means your LED lights much later than it should. Your locomotive will be going down the track with its lights out, only lighting as you increase the speed


see here

http://www.pollensoftware.com/railroad/

[cacole]

A 12 Volt Super-Bright White LED light bar from SuperBrightLEDs (http://www.superbrightleds.com) makes very good passenger car lighting with a minimum of additional circuitry; however, they are comparatively expensive. Most LEDs don't spread the light sufficiently for use in a passenger car without having to use several of them. The LED light bar mentioned above solves this problem; and they can be cut to length.

[AntonioFP45]

QUOTE: Originally posted by Don Gibson

tampico tony:

Nothing wrong with your 'mirror' strips, but some ALCOA aluminium foil can also be cut with scissors and glue'd to the roof.

-- Thanks Don. Also a good option since there is so much of that stuff available.

QUOTE: TRY NOT TO GET SUPER BRITE LEDs - using more is better - to eliminate luminant 'hot' spots.

Yes, on the photos I have of the RDC, you can see the points where each light is basically shining directly below it.

QUOTE: Train car lights are not blue. Only the glass is - (polarized).

- Yes, that is true. However, what I was referring to was that some white LEDs ( like the ones used on BLI locomotives), have a slight "blueish" hue to them. IMHO just like some floursecent lights. When we compare household incadescent and bright white flourescents, we can see just a touch of blue in the latter.

I had pointed this out when Walthers first introduced lighting kits for their Budd cars. The kits use incadescent bulbs, yet many prototype Budd streamlined cars were equipped with flourescent lights (I've ridden on the prototypes). With help, I hope to capture that appearance in my streamlined cars.

[cmarchan]

Budliner,

MisterBeasley is using DCC. The track voltage is always a constant 14 to 16 volts. Bridge rectifiers and regulators are used all the time with DCC.

MisterBeasley,

It is better to use an accessory decoder for your purposes. The reverse current produced by the 2nd phase of the DCC waveform can damage white and yellow-white LEDs ( they are more sensitive to reverse bias than their RED or GREEN counterparts). Accessory Decoders have circuitry that will protect the LEDs.

Another potential issue could occur if you do not limit the LED current. Stacking them in series solves the voltage drop issue, but a spike caused by a intermittent short across the track by an inductive device could be a problem.

[AntonioFP45]

Thanks for that info Carl!

I like the added benefit of the accessory decoder in that you can choose to turn lights on and off at will.

[GMTRacing]

Aren't the flickering lights prototypical? Especially on the electrified shoreline with gaps for bridges and slip switches and change overs for AC/DC conversion, I seem to remember lots of flickering. [:D]J.R.

[Anonymous]

You might look at using Surface Mount LEDS to avoid the problem associated with bleed through associated with traditional T1 LEDs.

Their small, top hat shape make them easy to mount in cars and they have a much wider angle of light dispersion than T1's.

Yellow/amber colors look very nice in older cars, but if you want flourescents, then LC-LED.com has some whites that mimic that color nicely.

Mike Tennent

[Anonymous]

You can also file the lenses off of LEDs to get rid of the focus lens which is what makes them "point source lights". In fact you can file them into shapes as long as you don't hit metal (and you can see that). You can also diffuse them even more with dull coat and alcohol or CA and accelerator to "frost" them. Colors can be added to white ones with nail polish.

Here's a link to a magnetic on-off switch I designed for just such use. It operates off of rechargable batteries and lasts for hours per charge. The batteries are hidden in the floor area. http://www.2guyz.info/Forums/viewtopic/t=1634.html
Fred

[AntonioFP45]

Aren't the flickering lights prototypical? Especially on the electrified shoreline with gaps for bridges and slip switches and change overs for AC/DC conversion, I seem to remember lots of flickering. J.R.

On prototype electric trains, such as subways, yes.  However over the years I've ridden streamlined passenger cars on Penn Central and Amtrak and never saw the interior lights flicker.

[MisterBeasley]

Well, since this topic surfaced after a couple of months in the high-numbered pages, I can give a progress report.

I have completed the lighting project in all 5 of my passenger cars.  Two already had big, single-bulb incandescents.  Those are original equipment, and they've got to be a half-century old.  Still burning brightly.  The other 3 cars came from eBay in 3 separate purchases.  I started with the boat-end Observation car.  I added a pair of red LEDs in the back, and two LEDs inside.  These I placed so they were near each end, but pointed towards the middle of the car.  With this arrangement, I ended up with reasonably uniform lighting throughout the car.  I used the same 2-LED arrangement in another coach, too.  In the last car, I found that the previous owner had installed some small flourescent tubes.  I cleaned up the contacts and re-soldered the connections, and they worked.  The eBay description said that this one came from an estate sale, so I hope this effort has brought a smile to someone in that big roundhouse in the sky.

So, I've got a complete set, all lit up.  Yeah, I can notice the 3 distinct colors of the lighting inside the cars, particularly the greenish hue from the flourescents, but I'm basically happy with the results.  I don't get much flicker at all on any of the cars, even though I went with the simplest approach - no rectifier, no capacitor, just the resistors and LEDs.

[MisterBeasley]

Huh?  Where did this one come from?  I saw it at the top, with my name as most recent poster.  I think the forum software has a problem with time-tagging when someone does an edit of a previous post.  So, who did let the dogs out?

[Vail and Southwestern RR]

Huh?  Where did this one come from?  I saw it at the top, with my name as most recent poster.  I think the forum software has a problem with time-tagging when someone does an edit of a previous post.  So, who did let the dogs out?

Excellent question!  I was getting set to agree with some and disagree with some, and then saw the date.  I wonder if the date gets reset if someone changes their signature, or something like that?  But then you'd expect a bunch of new 'old' posts.  Hmmmmm.......

 

[BigRusty]

You guys have got me thinking about the light distribution problem. Being a former lighting engineer for a major national commercial lighting manufacturer, I can attest that indirect lighting might be the solution.

Indirect lighting requires a highly reflective ceiling, usually white. But why not use the bright side of aluminum foil with almost 100% reflectance as someone sugested in an early post. Trouble is the lights would be shining down from it, when they need to be shining up.

I am thinking of using the flat type of LED glued at intervals along a styrene stirp with a pair of wires soldered along the contacts. One wire to the north truck and the other to the reversed south truck to provide current.

Since I am using DC I will need a consant lighting circuit and probably a capacitor to eliminate flickering. These could be placed in the vestibule or saloon out of sight.

Either a reed switch or an unobtrusive brass wiper switch on the car end would be nice too. It might be possible to install a reed switch on the underbody and run them over an electro magnet to turn them on or off.

 Just thinking outside the box!

[Vail and Southwestern RR]

Someone did a project, meant for lighting a billboard, that might work here.  You take a piece of copper clad PC board, pretty narrow, and scribe a gap down the middle of the copper, basically giving you two contacts.  Space surface mount LEDs along the strip, one contact on each side of the gap.  One end to power, one through a resistor to the other side of power.  To protect the LEDs from revers voltage in DCC you could put half oriented one way, and half the other.  They'll all look like they are on all the time, though they actually will be alternating.