LED Lighting

[piercedan]

Hey guys, I think I get what Art meant if my memory is still seving me well.

 

common values for 10% tolerance resistors are the following numbers:

 

10, 12, 15, 18, 22, 24, 27, 30, 33, 36, 39, 43, 47,  51, 56, 62, 68, 75, 82, 91, and multiply these by powers of 10.  

 

so 9.1, 91, 910 9.1k 91k are the values of resistors by powers of 10. 

 

When calculating values, you need to pick the closest number to what you need and err on te larger number to keep the current under the maximum for LED's.

 

[spikejones52002]

Art

AS I stated R= E/I with the fug factor to range between 20ma MAX to 16 ma MIN.

 Use the calculator built into your computer to find out what you can use.

Then use it again to figure out what wattage value, and use the next size up. What ever is common sizes.

I will not give any more examples so nit pickers will not compare apples to oranges.  940 is no where close to 91, ART. So if you want to use 22,33,and 47. That is your choice.

[Anonymous]

It's sort of nit-picking but 940 ohm resistor is NOT a common size.  91 is the 'standard' number, like 22, 33, and 47; so you would be able to get a 910 ohm resistor at your local Radio Shack.

Art

[piercedan]

Many LGB engines(read higher priced locos) have a voltage stabilizer circuit and supply 5 volts DC to their lights.

 Therefore a 3.6 volt LED with 20 ma and a resistor of 70 ohms is all that is needed.  Most common sizes are 68 ohms and 75 ohms.  I would go with 75 ohms and keep the current at 20ma or slightly less, never more than 20ma.

 

 How do you tell if the bulb is 5 volts from LGB?

 Very simple...   18 volt bulbs are the screw in type, 24 volt have round tops, 5 volt LGB bulbs have flat tops.

 Aristocraft SD-45's use a 4 volt stabilized circuit and the 3mm bulbs fit nicely into the head light lens.

 5mm worked on my USA 20 tonner.

 

 

 

 

[spikejones52002]

The formula for figuring the resistor needed is R=E/I.

resistor size = voltage applied divided by current needed.

REedited

I went to the two sites recommended. All Leds are 20ma.

18V/ 20  MA = 900 OHM resistor.

I would always go with the higher resistor.  900 = 940 ohm (I think is the common size). There is a fug factor.

The wattage of the resistor is figured by W= E X I.

wattage of resistor W = Voltage times Current

18 X .020 =  .360w and always use a larger or 1/2 watt resistor  for better heat disapation.

Keep this in mind.

LEDs are very sensitive to heat. When soldering do not hold the iron to the lead to long or trim the lead to close to the base.

all LED components are the same size. The jacket or bubble that surrounds LED is what determines 3 or 5 MM or what ever size you can use.

If you have the room. I use small twin lead male power connectors. The led leads slip into the connector. You can find these in most Hobby shops that carry R/C airplanes. They have a red and black lead wire.

Another source for components you never knew you needed,

"All Electronics" www.allelectronics.com at 800 826 5432

[grandpopswalt]

It seems obvious that you're running track-powered variable voltage DC (analog). I don't know if the LED's supplied with those engines are the standard 20ma/.6volt type or the newer 30ma/3.6 volt super brights (I'm assuming that the engines come supplied with LED's and not incandescent lamps).  The point is that if you're substituting the newer, higher current ones for the older type, then you would probably have to make some changes to the existing dropping resistor to accomadate the higher current. If you're replacing incandescent lamps with LED's of any kind you will have to add some sort of current limiting resistor. My guess is that an e-mail to Bachmann's and LGB's tech support folks will tell you what was originaally supplied and they may also tell you exactly what you need to do to make this change.

Good luck.

Walt 

[spikejones52002]

Cacole
Please reread and not read into it.
First, analog is the numeric change in values.
D,C, does not change levels.
Second, why would dougdagrump be changing an LED with another LED?

WE are just attempting to helpful. doundagrunp can read all suggestions and accept or dismiss any he wants.
 

[cacole]

Spike,

Please re-read the original question.  The user wants to replace the headlights in Bachmann or LGB steam engines that are operated on DC.

Bachmann G-scale steam engines use a 5mm yellow LED as their headlight, not a bulb.  All of the necessary constant lighting circuitry is already in the locomotive.

I don't own any LGB products so I can't say what their headlight is, but if it is an LED it also has all of the necessary circuitry on a board within the locomotive, so changing the LED is all that needs to be done.

For Toad Frog's comment about wanting to use LEDs for streetlights and buildings, your information about the need for bridge rectifiers, resistors, etc. may apply, depending on the power source he has in mind.

 

 

[spikejones52002]

?? Existing headlights = light bulbs??

You did not mention if you are using variable (analog?)or constant voltage.

Are you changing polarity for direction of run?

Lamps are voltage limited and LEDs are current limited.

Lamps will start to glow at any voltage (ever so dim). LEDs need a firing current, then their brightness changes slightly.

You can still use that old trick of placing a bridge rectifier in series with the motor. You will need a rectifier and a limiting resistor and get directional lighting. LEDs are not good rectifiers.

If your housing will accommodate two LEDs. Then you will have bidirectional.

[Anonymous]

Thank you, I also was going to use it like in street lights and so on. You know like on kitbash projects also. Again Thanks, Frog from the Swamp!

[cacole]

ToadFrog,

Two of the web sites listed mention that a resistor is needed in order to use their LEDs as locomotive headlights.  They are assuming that you are performing a new installation and are going to be powering the headlight from track power of at least 12 Volts DC for N or HO scale.  With G-scale, the track voltage can be up to 19 Volts DC at full throttle, so the resistor values they recommend need to be recalculated.

But if you're replacing one LED with another, as the original question indicated, the resistor is already there, somewhere on a circuit board within the locomotive, so you don't need to add one.

[Anonymous]

Since you're going to be replacing an existing LED, you do not need to be concerned about the requirement to add a resistor as mentioned on all of these web sites, because it is already there on the existing circuit board.

Hate to ask that question because I never was "info tech" in resistors, so can you explain or link?

[grandpopswalt]

Charles,

I hate to admit it but I have absolutely no experience with the new , bright super LED's". I understand that their characteristics are somewhat different from the the older more conventional LED's. Can you tell me What is the current draw and forward voltage drop? Are they available at Radio Shack yet? 

Thanks,

Walt 

Edit : I checked the websites you supplied after I posted (thanks for posting them). I've gotten the info I needed, thanks.

Walt 

 

[EMPIRE II LINE]

[user="dougdagrump"]My preference is to run, analog, in the early evening or at nite, which makes me wonder if there are any LEDs that can be used to replace the existing headlights on my entry level Bachmann & LGB steamers. If you look at the cover of "Electricity For Dummies" you'll see my portrait, just wondering if anyone mite have done it and would have any sources for materials. 

There's a guy on E-bay outta Canada who advertises Bright LED bulb and resistor sets for variouse voltages, I put one in my 2042 Mallet, looks real good, he lists under accessories listing I believe.....

Byron

[cacole]

Your best choice would probably be a super bright 5mm LED from http://www.superbrightleds.com/ or http://www.moreleds.com/

Both of these companies offer white super-bright LEDs that would be good to use for G-scale headlights, and possibly even passenger car interior lighting.

I'm not familiar with LGB lights, but Bachmann uses 5mm LEDs for most of their steam engine headlights.

My personal choice would be one of the 15 degree white LEDs from superbrightleds.  The higher the MCD rating, the brighter the LED, but at a higher current draw, too.

If you don't already know, LEDs are polarized and will not light up if you wire one backwards.  When you get a new LED, it will have one lead on the back that is longer than the other.  The longer lead is the positive, and you need to know which Bachmann or LGB lead is positive so you know how to wire the new LED into place at the correct polarity.  For that, you'll need a voltmeter.

If you want a headlight that truly looks like an incandescent bulb instead of fluorescent white, look for some Golden White LEDs.  Litchfield Station has 5mm Golden White LEDs as their item number LED 5 GW.

http://litchfieldstation.com/xcart/product.php?productid=290003&cat=22&page=2

Since you're going to be replacing an existing LED, you do not need to be concerned about the requirement to add a resistor as mentioned on all of these web sites, because it is already there on the existing circuit board.

[dougdagrump]

My preference is to run, analog, in the early evening or at nite, which makes me wonder if there are any LEDs that can be used to replace the existing headlights on my entry level Bachmann & LGB steamers. If you look at the cover of "Electricity For Dummies" you'll see my portrait, just wondering if anyone mite have done it and would have any sources for materials.