LED ?

[RR_Mel]

Because the foil is so thin it absorbs the heat from the soldering iron quicker than the resistor.  Tin and put a small blob of solder on the resistor and apply the heated portion of the resistor lead to the foil. In and out quickly.  I normally operate my iron at 750°.

 

I have run into soldering paste that had leakage but never enough to cause this problem.  I’ve been working with LEDs since they became available and never had one change value or get dimmer or brighter from a soldering iron.  They have either worked normal or quit as in dead.

 

I would have to say the manufacturing process failed or they weren’t from the same batch before you received them.

 

Like Dave said try them individually each with its own resistor.  Individually the brightness might be close enough that it isn’t as noticeable.  I series they will float at different level of light but might be forced using their own resistor.

 

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[gregc]

could it be the twisted magnet wire?   soldering the wires may have softened the insulation.

can you try unsoldering one leg of the dimmest LED

Measure the resistance from the ends of the wire where they are soldered in both directions.  in one direction, the forward diode direction, it should be low, in the opposite direction it should be infinite.  If it's not infinite, then there's a resistive path in parallel with the LED.

try to separate the twisted magnet wires all the way to the LED.   See if the resistance become infinite

after separating, see if it is brighter by holding the unsoldered end against the solder pad

 

[BATMAN]

Okay, after a quick visit back to my array, I may have had the ultimate DUH! moment. I have four SMD603s in a series, they are rated at 20ma forward each. Does this affect the other LEDs downstream?  Also, the #38 Magnet wire is rated at 35ma. I somehow had referenced a different package of wire I had. So am I right in assuming that either or both is the problem?  

[rrinker]

 No, and the current rating has nothing to do with it. The current rating of an LED is the maximum you can allow through it before it becomes a DED (dark emitting diode). The key parameter for series wiring LEDs is the forward voltage. If the rating is 3.5 volts, and you put 4x in series, the total voltage is 4 x 3.5, 14 volts. You will need a poer supply that puts out more than this. To calculate the current and resistor needed, simply treat the 4 LEDs as one, so now you have a 14V LED. Say you feed it with 16V. For a single LED, you take Vpowersupply and subtract Vled, and use this result and the desired current to calculate the resistor via Ohm's law, solving for R, so R=V/I. I should NEVER be the maximum from the LED rating, and definitely not over it. So we want half, 10ma - so you have your 16V power supply, 14V dropped across the 4 LEDs, leaving 2 volts, divided by 10ma (.010 amps) and you get a 200 ohm resistor. 200 ohms is only a standard value in 5% tolerance which isn't all that common. So you will have to go a little bit larger, for less current, or a little bit smaller, for more current. Either way, since we calculated at 10ma, you have plenty of room to go one size smaller resistor without exceeding the 20ma. For slightly less brightness, use the nearest higher value resistor, for lower current.

 Really that's all there is to it. If the LEDs are all matched, with the same forward voltages, then there should be no difference in brightness as each one will drop the same voltage, and the exact same current will flow through each of the 5 devices in series (4 LEDs and the resistor).

                                                --Randy

[BATMAN]

Thanks, Randy, what about running the four 3.2v/20ma LEDS through that Magnet wire rated at 35ma? Isn't that why the brightness varies?

 

[RR_Mel]

As Randy said “current isn’t the problem” and has nothing to do with it.

 

Is the difference in brightness disturbing?  If not go with them.  If it is disturbing then I would suggest you start over with matched LEDs, all from the same batch.  From what you have described the LEDs you are using are not matched.  They will work individually with their own resistor, you will most likely have to dink around with the resistor values to make them perfectly matched for brightness. 

 

I personally wouldn’t use SMD LEDs in a structure, to much trouble as well as undesirable light dispersion.  If size is the issue then go with the 1.8mm stovepipe LEDs and chop off the top, you would get more evenly dispersed light as well as more light per ma.

 

I use 3mm wide angle LEDs for interior lighting in my passenger cars and incandescent Grain of Wheat bulbs in my structures.  The wide angle LEDs would work much better in structures than the SMD or stovepipe.   

 

https://www.ebay.com/itm/3mm-Wide-Angle-Flat-top-Warm-white-Leds-Lamp-Light-Bulb-2-pin-10pcs-50pcs-100pcs/380913298290?ssPageName=STRK%3AMEBIDX%3AIT&var=650260655619&_trksid=p2060353.m1438.l2649

 

I model HO scale and for hanging or hooded lights I use 2mm GOW bulbs and even thou 2mm (7” diameter bulb) is a tad large they work fine for me.

 

 

I make my own lamp shades from 2mm washers.  I put one over the hole in a larger nut and press down using a ball tip allen wrench to give them a concave look.

 

I operate all of my 12 volt GOW bulbs at 8½ volts and I have never had to replace a bulb for burning out in over 30 years.  At 8½ volts they also look far more realistic than any LED.

 

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[BATMAN]

Thanks Mel.

In the first post showing what the array wizard showed, the last line at the bottom says "the array draws a current of 140mA from the source". What size wire should I be using to attach to the LEDs?

[RR_Mel]

The rating on #28 is 226ma, #30 is 142ma.

 

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[BATMAN]

Thanks, Mel, I guess my #38 @35mA is too small.

[RR_Mel]

Not for a single 20ma string.  I would use a heaver buss for the main feeder. I run minimum of #22 (920ma) for my lighting, #20 (1.5A) twisted pair (bell wire) is my normal lighting and turnout switch machine wiring.

 

I wouldn't run any LEDs at max current.  Like I said in an earlier post I rarely run any LED over 10ma, most under 2ma.  I have a few SMD LEDs, none over 1ma, they're too bright at 2ma for my lanterns.

 

These 3mm LED table lamps are running .5ma each.

 

 

The car below has a total of 8 LEDs and the meter is reading the total current at 4 volts, 2ma.

 

 

 

 

EDIT:

 

I corrected the LED count in the car above, the car with 12 LEDs draws 3.8ma at 4 volts.

 

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[rrinker]

 Two things:

Remember, the rating for a given wire size is the maximum it can safely carry. It doesn't take into account the voltage drop due to wire resistance. At least one chart has #38 at almost .7 ohms per foot. So depending how long the sections of #38 are, you could be significantly increasing the resistance - it will just act like you used a larger than 120 ohm resistor, but unless the LEDs out on really long strings you'd probbaly still be within the tolerance range of the resistor - which BTW I would use slightly bigger that 120, sonce that results in 20ma tot he LEDs and unless you are using precision resistors, one on the small side of the range may put too much current through the LEDs. Actually, if there is a noticeable difference in the brightness of individual strings of 4 LEDs, it could be the resistor itself. You may have to take a bunch and measure them with a meter and pick the 7 that are closest in actual measurement to make it all match up as evenly as possible.

Second - hmm, I forgot my second item - oh, more on the wire size, I think. When you connect loads in parallel, the current adds up, that's why seven groups of 4 LEDs, where each group of 4 draws 20mA, draws 140mA. So you DEFINITELY need thicker wire to feed that, #38 is far too small. Once the roof is in place, can you really see any of that without contorting yourself to a crazy angle to peer up from track level through one of the windows? I know Mel and others have posted using heavier wire as both the current carrying AND support for an array of LEDs over a large area. 2 birds, one stone.

Oh and Mel, using those LEDs as table lamps - amazing! From any normal view they look exactly like table lamps.

                                     --Randy

 

[RR_Mel]

Thanks Randy.

 

Actually they were a pretty easy build.

 

 

 

I spread the LED leads to .1” and plug them into a .1” micro connector from header strips.  I got the plastic beads at Hobby Lobby, very useful goodie.  I cut them in half for floor lamp bases.  The leads are coated with epoxy sanded and painted.

 

 

 

 

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[RR_Mel]

Brent

 

I was wondering, did you make the fixtures?  If so I can understand why you wouldn’t want to start over.

 

I would suggest you redo the copper foil on the beams.  Put a separate foil tape on each side of the beam, one positive and the other negative.  Solder one leg of a 1.2K or 1200Ω ⅛ watt resistor to one of the foils, doesn’t matter which one but do all of them alike, then solder one wire of your hanging fixture to the other leg of the resistor and the other wire to the opposite foil.  This would put the LEDs in parallel keeping the brightness of the LEDs closer to equal.  

 

The foil will easily carry the necessary current for all of the LEDs on all strings.  The current will add, say each LED drawing 10 ma at 12 volts will total 40 ma for each string.

 

Continue using the foil tape down a leg and attach your feeders there.

 

At 40 ma per stall you will need a power supply stout enough to power 40 ma times the amount of strings.  10 stalls at 40 ma totals 400 ma or .4 amps, not really a lot of current.  Another advantage is the ability to control the brightness of all the LEDs equally by varying the voltage.

 

I wired my roundhouse many years ago, long before SMD LEDs were available using 12 volt GOW bulbs.  Each bulb draws 50 ma so with 4 bulbs in 5 stalls I’m looking at 1000 ma or 1 amp at 8½ volts.  My feeder wire is #20 bell wire.

 

 

 

EDIT:

 

If you really want to run the LEDs at max current by lowering the voltage to 6 volts and using 330Ω ⅛ watt resistors the current will be about 20 ma.

 

 

 

Good luck

 

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[BATMAN]

RR_Mel

I would suggest you redo the copper foil on the beams.  Put a separate foil tape on each side of the beam, one positive and the other negative.  Solder one leg of a 1.2K or 1200Ω ⅛ watt resistor to one of the foils, doesn’t matter which one but do all of them alike, then solder one wire of your hanging fixture to the other leg of the resistor and the other wire to the opposite foil.  This would put the LEDs in parallel keeping the brightness of the LEDs closer to equal.  

This is what I had decided to do last night, I can still use the #38 Magnet wire for each individual LED giving it the look I want. I am never averse to starting over and decided a few days ago I would have to, no worries, that's how we learn.

I made the lights and can salvage the shades so the loss of four LEDs is nothing I went through more than that learning to solder the wire to them, they are so small there is quite a learning curve. I am sure they must be damaged after I put them through the wringer.

I plan on using this to control the intensity of the lights. I have a whole bunch of them I ordered from China for $.25 EA. Between these and the dimmer control for the room lights, it will be nice to play around and get the right settings.

 

Thanks for everyone's help so far, I am sure I'll be back for more.

[gmpullman]

Here's one of my initial tests of my nine-stall roundhouse lighting:

RH_lights3 by Edmund, on Flickr

For the general area lighting I used "string lights" cut into seven LED segments and run perpendicular to the stalls. Of course, toward the front there was a little extra wire and toward the back I had to stretch them out.

IMG_4762 by Edmund, on Flickr

I believe the LED spacing is around five inches.

These are SMD LEDs wired in parallel on two epoxy-coated solid copper lines. I simply cut to length and figure the appropriate resistor to give the brightness I desire. They are wired in groups of two so that third wire can be removed after cutting the lengths you want.

IMG_4760 by Edmund, on Flickr

IMG_4766_fix by Edmund, on Flickr

 

 

 The middle stalls I have added extra lights to illuminate the running gear. I saw this detail on some of the interior photos of roundhouses.

RH_lights4 by Edmund, on Flickr

Then there are the outside goose-neck lamps. In all I believe there are 97 LEDs. I never measured the total current draw.

Good Luck, Ed

[RR_Mel]

Brent

 

WOW!  If you had posted that picture earlier the answers would have been quite different!

 

Those Buck Converters work great for lighting power.  I use them everywhere.  The higher current Buck Converter work excellent for my high current needs, I’ve got a sack load of them too.  My GOW bulb current is up to 7.6 amps at 8½ volts.

 

I’ve been soldering SMD parts pretty regularly for about 5 years so I hopping I’m over the learning curve, I’ll find out later this week.  I ordered some tri-color SMD LEDs for my signals from Mouser.

 

https://www.bivar.com/portals/0/products/SMTL4-RGY.pdf

 

Good Luck on your lighting project.  If you want to get away from the magnet wire I found some #36 Litz wire with Teflon insulation on eBay for my signals.  Even at low voltage enamel insulation doesn’t give me a warm and fuzzy feeling.

 

Soldering #38 Litz wire to the SMTL4 LEDs will be a challenge for me, I might have to wait until after the cataract surgery to my left eye on the 1^st.  My right eye is doing good after the surgery last month.

 

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[BATMAN]

Okay here is round two. I need to take some photos when it gets dark with the intensity turned down but so far I am a happy camper. What do you think about how low to hang them, what looks best, 1-2-3 or 4.

You can see the resistors on this side.

 

The other side.

 

These were very tiny and somewhat intimidating to work with. With a little practice, it becomes very easy to solder this stuff and it is much more robust than I thought it would be.

I think tomorrow I will paint some sort of glue along the edge of the copper tape as I don't know what time will do to the sticky factor of the tape. I will paint it as well, in fact, the paint may be all the glue it will need.

Can those little SMD resistors be painted? 

[RR_Mel]

I haven’t had a problem with the tape coming loose on my Athearn passenger cars but they’re plastic, it might hold a lot better on plastic.

 

You light look very good!  Well worth your effort.

 

Are they wired in series or parallel?

 

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[BATMAN]

Thanks Mel. 

They in parallel hooked up to the copper tape on each side of the beam. Can those resistors be painted?

[RR_Mel]

Sure, paint them.  Just don’t us a metallic paint.   I’m very impressed with your lights!!!!  Quite a bit of tedious soldering.  Well worth the effort.

 

I’m curious about the current.  Did you redo the LEDs or go with new ones?  Can you measure the current of one string?

 

I’ve never considered using hanging light fixtures.  Neat concept.  I've used the tiny LEDs in lanterns.

 

 

 

 

 

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[hon30critter]

Hey Brent,

I'm glad that you have solved the problem. The lights look great.

As far as the height is concerned, as long as they can be seen through the windows, I would go with whatever looks good to you.

Thanks for sharing your experiences with the roundhouse lighting. I'm approaching the same point in constructing the roundhouse for the club and I want the lighting to look good. I already have the copper tape on order.

I have to say that I am really tempted to use incandescent bulbs like Mel does. I have never been totally happy with the colour that LEDs give off, and I have tried several different methods of adjusting the colour.

Dave

[RR_Mel]

Dave

 

As far as I’m concerned LEDs can’t cut the mustard compared to a Grain of Wheat incandescent bulb operating at or around 70% voltage when it comes down to realistic looking 1950s lighting.

 

They do draw a lot more current than a LED but unless you have upwards to 500 or so (25 amps x 8½ volts = 212 watts) I’ll go for it.

 

I’m running close to 8 amps from my 8½ volt output Buck Converters so that comes out to about 170 GOWs on my layout.  And so far I haven’t had one burnout; some have been operating for close to 25 years.

 

The Buck Converters are relatively new on my layout, about three years.  Before the Buck Converters I use transistor regulators, massive heat generators at high current.  Little or no heat at all from the converters or switching power supplies.

 

With the addition of the Arduino Random Lighting Controllers I have about 150 GOWs in 8 very realistic looking two story 1940s style homes doing their thing.

 

I scratch built a home for my wife and I as well as one for each for our seven children for my layout, we live as a group in Susanville on my layout.

 

I must confess, I do use a few LEDs in my structures, a flickering orange and flickering yellow together do make a great looking fire in a fireplace.

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[BATMAN]

I quickly slapped on a coat of paint over the copper tape, I think it needs a second coat but seeing as how it is just a mock-up I won't bother.

This was taken in daylight at 7volts. I think this will be good, time to get to work on the actual RH install, I wish I had installed the lights before I built the RH.

How do you guys install the Buck converters under the layout? My whole RH/TT lifts out as a unit, can I just screw the converter to a small piece of wood glued to the underside?

[RR_Mel]

BATMAN

 

How do you guys install the Buck converters under the layout? My whole RH/TT lifts out as a unit, can I just screw the converter to a small piece of wood glued to the underside?

 

 

I mount all of my Buck Converters in my control panel with a volt meter glued to the top for easy monitoring and maybe change the brightness easier now and then.

 

This is an earlier picture during one of my control panel upgrades.

 

 

I ended up mounting 5 converters in the left compartment and one in the middle with a seventh on the way.  My latest venture is a seven channel 1.4 volt flasher for the emergency beacons on my vehicles driven by an Arduino Nano.

 

The left compartment is for my Arduino stuff.  I now have a second card shelf, room for 16 Arduinos now.

 

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[rrinker]

 You can just screw it to the bottom of the base for the removable section, they you only have the two input wires to disconnect 

                              --Randy