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Discussion Starter · #1 ·
Hi all,

I have seen SMD LED's and was wondering if they are suitable to be connceted to a decoder in locos ....... or would the voltage given out by the decoder be too much for them also how do they wire up in comparson the normal LED's eg: what value of resistor should be used as a general rule,do they have the same life as a normal LED ?
 

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Hi Nick

Martin did some installations with SMD LEDs They need a resistor about the sam value you would use for a White or Golden white LED

3.4v is the operating voltage TCS do a special line of them

Here is some info on their LEDs
I've got some and one day will get around to putting them in a small Loco but they are so tiny Its hard to work with them

Regards Zmil
 

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Hi Zmil,

Many thanks for the information
........... they should be tiny enough for some of my locos where a 3mm LED gives off to much light no matter how much sheilding for the light is given, it may need some boxing in but with the reduced size of them it will be easier.
 

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I agree the resistor is the same as for a normal LED of the equivalent colour. In fact the actual LED is probably the same too, just mounted in a smaller package. The Farish Class 60 and 66 use surface-mount LEDs, never checked the white but the red has a series resistor of around 1.5k on the PCB.
 

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*** I was actually the first to offer a properly tinted SMD LED for Railway models and still supply many other companies with them.
They do indeed use the same sort of resistor values that are used for larger LED. I still have the widest range of MRR and especially "prototype white" LEDS available anywhere. (Prototype white is my own descriptor / trademark)

an image of one is attached - it was reviewed several years by Phil Grainger in model rail magazine.

The resistance needed for any LED will depend on the prototype being modelled and the way the light is to be transmitted from LED to the exterior of the loco body - if it uses light tubes such as is common with EU prototypes then 640 ohms is minimum and 1k is about right/always safe. With White they are always MUCH brighter than standard colurs so minor resistance differences are irrelevant.

The range of resistance that can be needed is extreme. If its to be used as an oil lamp equivalent then up to around 80k may be needed.

Upnick, there are several LED suitable for N scale - anything from 3mm to 2mm tower types, 1.8mm microdot and 0.8mm SMT will work in any scale. HOW you use them is the key... in some cases, even in N for example, 3mm is the best choice.

Richard
 

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Hi Richard,

My reasoning for looking at SMD's is some of my locos have lightobards and a headlight to be fitted not always with LGR so fitting an SMD in the roof of a loco additional to a 3mm type was a possiblitiy i was looking into if only the main light is needed indeed a 3mm Led with a heatshrink sleeve is fine, though i model U.S. outline so at times need the light to cover both boards and the main light in a very restricted area.
 

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Hi All

Richard do you do any Little SMD LED that are prewired?

I'm not at all confident I can solder an SMD without frying the LED (no tails to take the heat away)
I have an elcheapo regulated iron 200-450 degree C , on the TCS website it says "heat applied for no longer than 1 sec"
and with shaking hands that may not be a reality

There are some suppliers in the US that sell with wire added Here

After I have had a go with the Flicker free units (which will take me a while) I would like to try to install some SMD's in a little 0-4-0

Regards Zmil
 

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***Hi Zmil
Those wired SMDs are over 2x larger than those I sell - they are 1206 or larger by the look of it!

soldering SMDs is a skill that takes time to learn but its not hard. You do have to be really careful not to rip the solder pads off the LED after soldering wires to it... I find it helpful to let it cool and then paint all over the end of the wires and LEDs solder pads with super glue, letting that dry overnight to stiffen up/reinforce that area.

No, I don't intend to sell SMT with leads, but we will soon do a super tiny LED with fine leads that will make you happy (appx Decemder with luck)

Richard
 

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QUOTE we will soon do a super tiny LED with fine leads that will make you happy (appx Decemder with luck)

Look forward to seeing them Richard
sure i can make use of them

*** Zmil***

I use a 1mm iron tip for all wiring work so only a momentary touch is required .. though a flat angled one for track work remembering to change them before heating up is my problem


I have practiced soldering on a thin strip of brass before today with the iron with off cuts of wire cheap but effective way to get used to the iron.
 

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Discussion Starter · #13 ·
QUOTE (zmil @ 18 Nov 2008, 05:42) <{POST_SNAPBACK}>Hi All

I have spotted some 0603 Red SMD LEDs (50 for $10 free post)
I may get them to practice on before I try the real ones
and once I have that sorted , I can use the remaining (survivors) for Tail lights on wagons

Regards Zmil

Got finally to te bench yesterday Zmil on opening the packet to get one of the SMD's out it was dwarfed by the reisistor they aeee so tiny (try and take a pic for comparison later and post it) i was a bitg tired and tried soldering it up but it decided to climb the iron and destroy itself
have another go later ....... buying wired ones may be the way to go but i will persist with these first.
 

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Got some of the SMD's sorted today using the iron to heat the wire to solder it up a touch of flux on the wire soon as the iron makes the flux sizzle its done ....... then a covering of superglue to seal the wires on to the SMD itself, tested on a 9v battery they are bright for their size.



 

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Nick I have mentioned it in Zmils thread a tip I have learned.

Use double sided tape, stick one end on to your bench and stick these little critters on to the other so no chance of them to wooble around when soldering. Use lacquerd wires.

Baykal
 

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QUOTE (ebaykal @ 28 Nov 2008, 15:28) <{POST_SNAPBACK}>Nick I have mentioned it in Zmils thread a tip I have learned.

Use double sided tape, stick one end on to your bench and stick these little critters on to the other so no chance of them to wooble around when soldering. Use lacquerd wires.

Baykal

Saw the tip Ebaykal thank you got the double sided tape out now
 

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QUOTE tested on a 9v battery they are bright for their size.

Glad you posted that test pic, I wasn't sure where the LED was


David
 

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Discussion Starter · #19 ·
Great link Martin thanks
i am looking at adding MSD's for ditch lights on a couple of locos might try with HO first though
 
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