Resistors and Converters for LED Bulbs

Ebay

Charlie

The smallest LEDs I have found are the 2mm Ceramic. Unlike the one you have pictured they are 2mm for their full length. The flange on yours is greater than 2mm. Lionel, MTH, and K-Line use these in their class/markers. I have not seen them in white though. You should be able to put a 3mm white LED in the headlight.

Pete

Hmm, I might have to purchase the MTH yellow 2mm versions. If so, what resistors and/or other pieces will be needed to operate in 18V Command environments?

For LEDs you will always need resistors, you will also need rectifiers if you are running off track power. Just put a resistor inline with your current LEDs and connect them to the ERR board

3MM flangless LED's should work for the headlight, they had a 3mm bulb in there.  The ceramic ones that Pete mentions come in amber.

Since I wanted to keep the class lamps illuminated constantly like the headlight (as per real life operations), I decided that I needed an AC/DC converter to hook up to them (the 2mm ones that Pete mentioned for 1.7-2.2 V).

However, I can't quite find one for this. What type do modelers typically use for this situation? And how much resistance would be needed for them?

Mikado 4501 posted:

2 yellow/amber bulbs for the classification lights (since the real engine had amber lights, not red)

Any help is appreciated.

Mikado,
The class lights were only two colors. White (not yellow ) for extra train, green for second section following or they were extinguished.

Jim,

I'm going by the photos during its green painted age, and most of the photos (if any of them showing them on) show the lights with a bright yellow color. I guess its the lenses that make the white look yellow.

Aside, the bright yellow at least looks more accurate than the red, and MTH has been giving its Mikados yellow class lamps for years and no one complains there.

Mikado,

And who said MTH knew what they were doing? I actually did complain when they first started this stupid practice.

I am trying to teach you something here. Class lights were not yellow. But, you do what you want. And remember you were the one that asked for help.

Jim,

Everyone has their own tastes. I understand that you're trying to help, and I realize I'm not correct all the time, and it is just my opinion. I for one see that not all class lights were green and very little if any were red. No need to get hostile about it, though.

Mikado 4501 posted:

Since I wanted to keep the class lamps illuminated constantly like the headlight (as per real life operations), I decided that I needed an AC/DC converter to hook up to them (the 2mm ones that Pete mentioned for 1.7-2.2 V).

However, I can't quite find one for this. What type do modelers typically use for this situation? And how much resistance would be needed for them?

Why go to all that trouble?  You can use a resistor and diode and power them from track power.  You don't need an AC/DC converter, unless you consider a 5 cent diode and AC/DC converter.

Fair enough John,

Which diodes and resistor do you use for situations like this?

Mikado 4501 posted:

... but I can't seem to find grain of rice bulbs on their site that can fit into the classification lights. I don't think the 1.8 mm bulbs will fit because the opening in the lamps is so skinny.

For markers, I'd consider a 1N4003 (my standard diode for most uses), and a 1K 1/4W resistor.  If they're too bright, just go up to a 2.2K 1/4W resistor.  With two markers, if you wire them in opposite polarities, you can dispense with the diode as the they protect themselves from reverse voltage, see illustration below.

For LED headlights, I use a 470 ohm 1/4W resistor and the same diode.  If I have two headlights, I wire them as above if using track power and dispense with the diode.

Remember, if you're wiring from the TMCC headlight outputs, those are half-wave DC with positive ground for command operation, but full-wave AC for conventional operation.  That affects how you wire them over just using track power.  You will need the diode as you can't wire multiple LED's as above, they must all have their positive leads going to frame ground.

I normally run markers/class lights at much lower currents (and brightness) than headlights.  I think the locomotive looks kinda' silly when the class lights are brighter than the headlight!

A basic rule of thumb with a single 20ma LED is take the value of the DC voltage applied, subtract the operating voltage for the LED (3V for white/blue, and 2V for most others), and then multiply the result by 50.  That's the minimum resistance you should ever use for the LED.  For rectified track power, I consider the voltage to be 9V DC.  For a white LED headlight, that would be 6V to drop across the resistor or 300 ohms.  I don't like to run that close to the maximums, so my value of 470 is my standard.  For the class lights or markers, I usually go larger with the resistor to achieve the desired brightness.

The 2mm ceramic lights should fit.  The fiber may be problematic as you have to make a 90 degree bend out of the boiler front into the class light fixture, fiber won't bend that sharp.  Also, most of the light from the fiber is out the end, that would be point in one direction if you could get it stuffed into the class light.

That's a good point.  To solve the right-angle "bend" problem or for multi-directional lens fixtures like on a caboose the trick is to file/sand the end of the fiber so that the light scatters sideways (rather than only going straight out the end).  This is illustrated below for the forward and rear facing door/brake lights on an Amtrak passenger car.  Photos pasted together from another thread.  Modern LEDs are so bright/efficient that there is plenty of light to go around so-to-speak!

If you need smaller LED's .  Look here.  These are 1.8 and 1.6mm.

http://www.led-switch.com/1.6%20LED.htm

John,

Since I'll be buying the Super Chuffer as well, and I'll be buying the headlight, back up light and firebox light from here: http://www.modeltrainsoftware.com/bl-212.html to hook up to it, I just need what to hook up for the class lamps to track power, not to the TMCC board, so they'll stay lit no matter what direction the engine is going. So, I think I'll opt for the first method wiring in opposite polarities. For the record, I've already purchased the 2 yellow 2mm LED's from DigiKey.

I'm pretty sure I can find these components at Greenbrook Electronics.

Patrick1544 posted:

If you need smaller LED's .  Look here.  These are 1.8 and 1.6mm.

http://www.led-switch.com/1.6%20LED.htm

Look again.  Those are 1.8 & 1,6mm in name only.  Check the size of the base.  It's 2.1mm x 2.2mm, and the leads come out the side of those, even a bigger issue.  The 2mm ceramic ones are the smallest readily available, trust me I've looked.

Mikado 4501 posted:

John,

Since I'll be buying the Super Chuffer as well, and I'll be buying the headlight, back up light and firebox light from here: http://www.modeltrainsoftware.com/bl-212.html to hook up to it, I just need what to hook up for the class lamps to track power, not to the TMCC board, so they'll stay lit no matter what direction the engine is going. So, I think I'll opt for the first method wiring in opposite polarities. For the record, I've already purchased the 2 yellow 2mm LED's from DigiKey.

I'm pretty sure I can find these components at Greenbrook Electronics.

You do NOT want an Evans LED for the Super-Chuffer LED headlight.  It must be a BARE LED with no resistors, capacitors, diodes, etc.  The Evans LED's will work for the class lights, but I don't think they offer the ceramic 2mm ones.  They're really the only ones that I've found to fit many of these applications, and it's also the reason that Lionel, MTH, and other makers use them in many locomotives.

I didn't  see those dimensions before I suggested them. I have the 2 mm ceramics myself and they are perfect enough for me.  

It would be nice to find some smaller solutions, but so far I've come up dry.

Some of you guys like to make things complicated. I like simple. And simple is to use LEDs for 18v from model train software. Clip the oversize led form their circuit and use the smaller ceramic or other mini led from the oversize led place. Boom! You are done!

John,

You're right. They don't offer 2mm LED's, hence why I ordered the ones from DigiKey.

I'm still going to hook up the class lamps the first method with the 1K 1/4W or 2.2K 1/4W resistor, since it seems alright for both conventional and command environments. I'll just hook up the Evans ones to track power (back up light to TMCC board of course), and I don't mind having the headlight on all the time - I almost never see real steam engines turn them off in reverse.

prrhorseshoecurve posted:

Some of you guys like to make things complicated. I like simple. And simple is to use LEDs for 18v from model train software. Clip the oversize led form their circuit and use the smaller ceramic or other mini led from the oversize led place. Boom! You are done!

You pay a couple bucks at least for ten cents worth of parts, a resistor and a diode.  You're already going to solder, so I'm failing to see how that simplifies things.  It empties your wallet faster, you could view that as simple.

Big Jim posted:

I am trying to teach you something here. Class lights were not yellow. But, you do what you want. And remember you were the one that asked for help.

Maybe, but the old incandescent bulbs they used probably look more yellow than white when you're installing LED's.  Add to that the fact that no good alternative exists to actually put white LED's in those class lights and yellow seems to be a decent options.

gunrunnerjohn posted:

Big Jim posted:

I am trying to teach you something here. Class lights were not yellow. But, you do what you want. And remember you were the one that asked for help.

Maybe, but the old incandescent bulbs they used probably look more yellow than white when you're installing LED's.  Add to that the fact that no good alternative exists to actually put white LED's in those class lights and yellow seems to be a decent options.

Well, that is total BS and the only thing you are trying to do is be argumentative! I figured that someone would bring up color temperatures here and I figured you would be the one to do it. 

When MTH went to the yellow diodes in their class lights, they didn't look a bit "incandescent white"! They looked just like what they are and that is yellow!!! You could tell looking at the models from a good distance that the class lights were yellow and nothing near the same color as the headlight. Yet, people would go to their grave defending MTH thinking that they could do no wrong!

Class lights have been discussed here on the forums many times over by a lot of people. Nationwide, the rules call for an extra train to fly WHITE flags by day or WHITE lights at night. The rules do not provide for the color yellow in "Class Flags or Class Lights"!

WOW, time to switch to decaf!

gunrunnerjohn posted:

For markers, I'd consider a 1N4003 (my standard diode for most uses), and a 1K 1/4W resistor.  If they're too bright, just go up to a 2.2K 1/4W resistor.  With two markers, if you wire them in opposite polarities, you can dispense with the diode as the they protect themselves from reverse voltage, see illustration below.

For LED headlights, I use a 470 ohm 1/4W resistor and the same diode.  If I have two headlights, I wire them as above if using track power and dispense with the diode.

Remember, if you're wiring from the TMCC headlight outputs, those are half-wave DC with positive ground for command operation, but full-wave AC for conventional operation.  That affects how you wire them over just using track power.  You will need the diode as you can't wire multiple LED's as above, they must all have their positive leads going to frame ground.

 

I plan to install LED marker lights on a tender, using track power.  Can you advise on the correct "orientation of the diode and LED anode, related to center rail? (or does it matter, as it is AC?) 

I would like to replace the rear backup lamp with an LED, connected to the TMCC output. The existing lamp has a two wire connection; one is common with frame ground which you stated is positive (go figure).  Does the diode and anode side of the circuit get connected wire common to frame ground, and the cathode to the other existing wire?  

Will a 1N4001 or 1N4007 diode be satisfactory, in lieu of a 1N4003 ? ( I have a few of each).

The "warm white" LED's are still too white for my liking.  I tried putting a thin coat of acrylic paint on one, with more satisfactory results to produce a glow more consistent with an incandescent bulb; however, I could not achieve a coating thin enough, yet uniform so it was not blotchy.  Going to try a thin coat of lacquer (nail polish).

gunrunnerjohn posted:

It would be nice to find some smaller solutions, but so far I've come up dry.

The HO guys use 0402 SMT LEDs but that's a delicate solder job for most.  

Lou N

Lou, 0603 is my self-imposed limit for parts.

Jim, the band of the diode MUST face the positive pin of the LED when you connect to AC.  Both the LED and the protection diode do have polarity.

Try Amber LED's, they go more to yellow.  If those don't do it, try yellow.

Will a 1N4001 or 1N4007 diode be satisfactory, in lieu of a 1N4003 ? 

What's the difference?

gunrunnerjohn posted:

Lou, 0603 is my self-imposed limit for parts.

Understood.  I did a board a few years back that was a sonar transmitter used to track spawning salmon.  It sat on a dime with room to spare.  All 01005.  The technicians we have that do in process inspection and touch up are just amazing.  And the pick and place machines do 12,000 parts/hour.

The wire bonded LED die I am currently using are 12 mil square.  I laid out the board; 1/16" x 2".

And the boards are 1 mil thick kapton.  One thing for sure, there's a 10x loupe in every one of my lab coats.

Lou N

I don''t see that the voltage (track  or TMCC headlamp) exceeds the rating of the 1N4001;it should be OK correct?

Is there any harm in using the 1N4007, which is rated for MUCH higher voltage?

Any 1N400x part will do where X is from 1 to 7.  There is no difference in our applications with low voltage.