Lighting buildings - Jim Banner

[glsummers]

Jim Banner; I know you know the answer to this question if you get this question. I was given a whole lot of white Christmas tree lights and I experimented with them and they kept blowing out. I cut them off the string and put up to the AC in a transformer and it blew immediately; I also tried to use the DC on a transformer and the same result occures.  How can I use these inexpensive (free) lights to light buildings with out blowing out the bulbs? How can I use a dimmer to where they would not be so bright. Any help would be appreciated from anyone. Larry

[hunter2115]

Check this link- it may answer your questions. I plan to try this myself.

http://www.billsrailroad.net/bills-lights.html

[Jim Banner]

Larry,
Hunter has posted an excellent link on the subject.  I do much the same thing except I put six of those 2.5 volt bulbs in series in a "mini string" and connect the mini string to a 12 volt transformer.  That extra extra bulb does 3 things.  (1) It reduces the light output a bit so that the bulbs are not so glaringly bright.  (2) It increases the life of the bulbs from about 250 hours to approximately 5000 hours.  And (3) it shifts the colour of the light slightly more toward the red end of the spectrum.  This effect is subtle but it is enough to make our models look like they have incandescent lighting compared to the "sunlight" in our train rooms, which is usually incandescent or warm fluorescent.

Note:  The following paragraph is a bit technical and rather boring, so you might want to skip it and scroll down to the "Conclusion" below.

There is one problem with these lights that you should be aware of.  Many of them are designed to bypass any bulb that burns out.  In normal service, it works this way:  each bulb is fitted internally with a ring of wire with a voltage sensitive coating on it.  At low voltage, this coating does not conduct electricity.  So when the bulbs are all getting just 2.5 volts each, it is just like the rings are not there.  But if one bulb burns out, all 120 volts coming from the outlet is applied to the coated wire in that one burned out bulb and the coating burns off, letting the wire ring short out just that one bulb.  Then the 120 volts is divided among the remaining 49 bulbs which light up more or less normally.  With a mini string operating at reduced voltage, there is not normally enough voltage across a burned out bulb to burn off the coating, so all 5 or 6 bulbs in that string go dark when just one bulb burns out.  (A good reason for extending the bulb life by using 6 instead of 5.)  There is a small chance that your bulbs will react to 12 volts and burn off the coating at a lower than normal voltage.  So if one bulb on a 5 bulb string burned out, that would leave 4 bulbs working at 3 volts each, reducing their expected life to about 25 hours.  When a second bulb burns out (and it will, with this shortened life) the other three will have an expected life of about 1/2 hour.  So out goes the third bulb giving the last two bulbs an expected life of about 10 seconds.  Then the fifth bulb will go, and as you have noticed, one bulb with all the voltage across it will go quickly.  My calculations show 1/1000 of a second, or about the time it takes your camera to flash.  Usually this will not happen because the coating on the wire ring will withstand more than 12 volts.  But here is the kicker - if the bulbs do short themselves out as them fail, you will end up with a dead short across your transformer. 

Conclusion: use a fuse to protect you transformer or other power source.  For a small, trainset power pack rated 8 VA, a 1/2 amp fuse would be good.  For a 16 VA supply, a 1 amp fuse.  If you are using a computer power supply, do not use a fuse larger than 5 amps even if the supply can handle more - chances are the wiring under your train table cannot.

An alternate source of small bulbs is rope lighting ($16 CAD for a string of  100 at Wal Mart.)  These are long life bulbs rated 10,000 hours at 3.6 volts.  On my latest railway (0n30 in 1900) I use them in parallel across the 3.5 volt output of a computer power supply (fused, of course.)  I find this more convenient than having to have a fixed number of lights in each building or having to split a mini string between multiple buildings.  These are more expensive than the Christmas lights but at 16 cents each, they are still far cheaper than grain of wheat bulbs from the hobby shop (same physical size.)  But of course they cannot compare in price to Christmas tree lights that someone gave you!

Jim

[pdlethbridge]

headache time uugggg

[CNE Runner]

Jim - You bring up another subject that has been 'haunting' me: LED lighting. From what I can gather, at the Model Railroad forum, the resident pundits are now switching to LED structure lighting because LEDs: produce less heat, use less current, and last longer. Is there a website that explains (to the electrically challenged) how to install LEDs? It seems that incandescent bulbs are not the way to go in structure lighting. In the RV industry, incandescent bulbs (found in motor home lighting) are rapidly being replaced by LEDs. Your thoughts?

Regards,
Ray

[Jim Banner]

PD,
My apologies.  I forgot the headache warning.  Sorry. 
I won't forget this time - HEADACHE WARNING!!!

Ray,
I have played around with LED lighting and gone back to incandescents.  Miniature incandescent bulbs throw light in all directions.  If you hang one in the center of a small building, it will shine out all the windows.  If you use paper curtains in your windows, or you sand the inside of your windows with 600 grit to make them look a little dirty, the one bulb will light up all the curtains and "dirt."

LED's throw a cone of light off the end.  The cone is about as narrow as the beam of a full size spot light bulb.  This is great if you want to light a display in a store window, but not much use if you want to light up all the windows.

Let's look at another application - street lights.  An old fashioned street light can be made of brass tubing bent into the shape of a candy cane, a washer hammered into a cone shape, and a small bulb or LED.  If you use a bulb, the light shines in all directions except up (because of the shade.)  The light is brightest on the ground under the street light and fades gently as you move farther away.  It will light up close by building fronts and even buildings farther away will be dimly lit.

Take the same street light but with a small LED.  It casts an intense, sharply defined pool of light on the ground beneath it and virtually nothing to the sides.  In H0, the pool of light is smaller than a dime.  This is generally not what we want for a street light, but there are exceptions.  Imagine this scene:  Down the street is a movie theatre, bright lights and all.  Well lit people waiting for the next show.  But the foreground is "down by the tracks."  Not much light here.  In fact, a single street light throws a feeble pool of light.  In that pool of light, a couple on their way to the theatre stops for a kiss.  A powerful visual contrast, all done with lighting.  The single street light would of course use an LED.  The more general lighting around the theatre would use incandescents and fibre optics.

There are a number of uses for LED's in model railroading.  Headlights for example.  Warm white for incandescent headlight.  Bright white for arc lights.  Cold white (blueish) for acetylene headlights.  Bicolour LED's for red/green signal lights.  Flashing red LED's for FREDS.  Tiny red LED's for rear markers.  Surface Mount LED's for ditch lights and in passenger cars.  Floodlighting of signs.  Light sources for fibre optics.  And just about anywhere that you would use a spot light in the 12 inch to the foot world.

You mentioned LED bulbs to extend battery life in motor homes.  The ones I have seen use multiple LED's pointing is all directions to get even illumination in all directions.  Some of these have over 100 LED's in them.  Others diffuse the light to make it spread more evenly but with a loss of efficiency.  So far, nobody has come up with a miniature LED with a large number of emitters.

Now about using LED's.  There are only three things you need to know:
(1) LED's run on dc.  The two leads found on most LED's are different lengths - the longer one is positive, the shorter on is negative.  If the LED has a raised ridge around its base, it will most likely have a flat spot next to the negative lead.
(2) LED's need a resistor.  Resistance is measured in Ohms.  You can figure out how many ohms you need this way:  figure out what voltage you are running them from (read the label, measure with a meter, or consult a ouija board.)  From this voltage, take away 3.  Whatever is left, multiply by 100.  This will give the resistance in ohms.  Use the closest standard size resistor.
(3) If the light is too bright, use a resistor with more Ohms.  You can go as high as you want without causing damage.  If the light is too dim, use a resistor with less Ohms.  You can safely go down to about 1/4 of the Ohms you calculated.  If the resistor overheats, use a physically larger resistor of the same number of Ohms.  Physical size is related to how many watts of power the resistor can dissipate.  Start off with a 1/4 watt resistor and work up if necessary.  Usually it is not necessary.

Okay.  Lets do a practical example.  I want to use an LED headlight in a locomotive that has a decoder in it.  In small scales, most decoders will put out about 12 volts.  So we take that 12 volts and subtract 3 volts for the LED.  That leaves 9 volts for the resistor.  Multiplying that by 100, we get 900 Ohms.  A close standard resistor is 1000 Ohms.  So we use a 1000 Ohm, 1/4 Watt resistor.   We connect one resistor lead to the long, positive lead of the LED.  If we are soldering close to the LED, we had better use a pair of hemostats on the lead right next to the LED to keep the heat from melting the LED.  Then we connect the other end of the resistor to the positive output of the decoder.  A quick check of the manual tells us that is the blue wire.  Lastly, we connect the negative lead of the LED to the function lead.  That would normally be the white lead for a headlight.  After running the light for a few minutes, we feel the resistor.  In this case it probably will not even be warm.

And there you have it.  Try a few - use a 9 volt battery to start if you want.  Before long, you will be installing LED's in less time than it takes to read the instructions.

Jim

[rich1998]

if some of you like to experiment, below is a link about led's and inverted cone led's. look around at night. you will see many different types of lighting fixtures, colors of lighting.
don't forget a view block in some buildings. multi story buildings to give the illusion of walls, floors between different building levels.
I like variety myself.
I am buying some inverted cone led's for strobes on the roof of my two 44 ton locos.

http://www.google.com/search?pz=1&cf=all&ned=us&hl=en&q=inverted+cone+led+model+railroad&btnmeta%3Dsearch%3Dsearch=Search+the+Web

very good reading with a lot of good links to keep in the pc.
lex

[Billm10454]

Jim, I have a question for you. I have some 3 volt grain of wheat bulbs. What size resistor should I use for them. Thanks

[bcjim]

PD,



LED's throw a cone of light off the end.  The cone is about as narrow as the beam of a full size spot light bulb.  This is great if you want to light a display in a store window, but not much use if you want to light up all the windows.

I have had good luck with some  larger surface mount LEDs
They are not a focused and appear to be in light fixture where I have them mounted on walls in buildings.
I have several sets of 3 LEDs in series, run off a 5v regulator.

Question for you,
have you pulled apart a string of LED Christmas lights?
I notice when I turn my head quickly near them I see a flickering effect.
Looks like half wave, am guessing they are only using one diode in the string?
Jim in Kelowna

[Jim Banner]

Jim,
That is exactly what they did the in strings I have pulled apart.  One of the neat things about LED's is that it doesn't much matter whether you power them with straight dc or pulsing dc or intermittent pulses - they still look about the same brightness.  It has to do with persistence in the eye.  So if you really wanted to extend battery life when operating passenger car lighting by batteries, you could use a circuit that turns the LED's on for a millisecond or two, then turned them off for 10 to 15 milliseconds.  The effect you noticed would be even stronger, but looking straight at the passenger cars, they would look about the same even though using 90% less power.  Taking movies of such a car - now that really would be a problem.

Lex,
I played around with inverted cone LED's some years ago.  Cutting the 90^o cone with a modified drill bit was no problem but polishing the cone right up to its sharp tip was.  Then they came on the market but in blue white only.  These worked well on Christmas trees but the colour was wrong for lighting buildings.  I see from your link that they are now being produced in ultra white ("daylight") but not yet in warm white.  Hopefully that will come.

I think your use of inverted cone LED's to make roof top strobes is an excellent idea.  Like real strobe lights, inverted cone LED's throw virtually all their light out to the side and very little out of the end.  This same characteristic makes them useful for building lighting but pretty useless as street lights or passenger cars lights.  Adding a drop of ACC into the cone showed some promise of redirecting some of the light out of the end and still leaving some coming out the sides, but I did not pursue this after I found strips of premounted SMT LED's which are an ideal solution for passenger car lighting. 

Last winter, I developed a constant current circuit for these premounted LED's.  It replaces the normal ballast resistor, and can work with a controller circuit which adjusts the current of a whole bank of the LED's.  These circuits, together with a constant voltage circuit to eliminate flicker from bad contact with the rails is what I intend to use in my 0n30 passenger cars.  They will be used on a portable layout being built for taking to train shows.  As such, the cars will be run in various ambient lighting for long periods making both adjustability and track power very desirable features.  I will probably do an article on this lighting once I have some more run time on the originals and have designed PCBs for the circuits.

Jim (in Saskatoon)   

[glsummers]

Thank you JIm and everyone else. That was a lot of great information. Thanks a lot. Larry

[lmackattack]

here are a few shots of lights on my layout. As jim has said Leds direct light. IMO better used for a headlight. I use regular 12-16v bulbs that are wired to a buss wire that is controled by an old DC powerpack. I run them at about 70% power to save bulb life. some of these pics I turned the power pack up to 100% just for the photos and they look very bright because of this.

Trent

[glsummers]

Awesome pics Trent!

Jim, one more question. When I cut the lights of the string there were three wires instead of two. I assume that the third wire is a ground. What and how do I hook up the third wire. Thanks.

[CNE Runner]

Jim, thanks for the reply...you answered my question completely. Trent: All I can say is WOW!!!

Thanks,
Ray

[lmackattack]

I think that the 3rd wires is used incase that bulb burns out the rest of the strand stays lit?