Can any of you veterans give me recommendations on which LED's & resisters to purchase when converting HO locomotives from Bulb to LED? The locomotives are LL proto 2000 (GP30), LL proto 1000 (F3A), and Atlas Trainman (GP38-2). Thanks!
I think most may say warm white or golden white for LED color, I went with 3mm for size. Regular white may be too harsh.
Resistors were 1k ohm 1/4 watt off ebay, I think a buck and change for 10 and free shipping, work very well and no complaints. I don't think LEDs are as sensative to resistors as bulbs from the research I've done.
The Backshops - A blog dedicated to modeling projects
The below link covers LED's and light bulbs.
http://www.members.optusnet.com.au/nswmn1/Lights_in_DCC.htm
I mostly used LED's and a 1k, 1/4 watt resistor.
LED's are current devices and light bulbs are voltage devices. Little different when you start measuring the operating characteristics.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
IDRickThe locomotives are LL proto 2000
For me, these pre-wired and pre-resistored LEDs are quick and easy, plus nearly a direct replacement for the size and shape of the L-L/ Atlas, etc. lamp:
https://tinyurl.com/yy77qgtr
Again, I said quick and easy. There are LOTS of variables out there. On steam locomotives I generally use an SMD carefully cemented into the headlight housing.
Here's a pair of the WeHonest LEDs temporarily taped into the original location of the L-L lamps:
B_O-SD7 by Edmund, on Flickr
and one installed into an E-8:
LL_E8_DCC2 by Edmund, on Flickr
Look around the WeHonest offerings, there are several choices similar to the one I linked to above, both in size and color.
Sometimes I add other LEDs to illuminate the number boards separately as I like to see these lit all the time.
In HO diesels we usually have the luxury of lots of room inside to play around.
Good Luck, Ed
Thanks for the links, very helpful! Do I need to worry about which lead is the + and - when installing? Is there an accepted uniform color coding that red is always (say +) and black is always (say -)?
Ed, I always appreciate that you take the time to add some helpful photos! Looking at your pictures, I see the LED fit neatly in the manufacturer's groove and are temporarily held in place with tape. What do you use to hold the LED in place as your final installation step?
Another question a bit further afield. I know you've done many DCC installations and have done some milling on the chassis. Depending on which combination of decoder + speaker that I use, there may be a need to mill out the manufacturer's groove for the rear headlight. How do you in attach the LED headlight in this situation and how do you focus the light out the rear headlamp lens? Thanks!
Polarity matters, but hookign the LED up backwards, as long as the resistor is in the circuit, won;t hurt anything, it just won't light up. LEDs don;t have color coded leads, however they do usually have a flat filed in one side of the case, insteadof being perfectly round. The flat side is the cathode, the - side. One lead is usually longer as well, but once you cut them to fit you can't tell that.
On a DCC decoder, the function wire, white, yellow, purple, green, etc. is always the - side, the blue is the common for all lights or LEDs and is the + side.
It does not matter which side of the LED the resistor is on, it just has to be there. For consistency though you should pick a side and always wire them the same. Electrically it makes no difference.
T1 (3mm) size LEDs fit in the spot in the P2K chassis where the light bulb was, at least on my Geeps.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Thanks for the helpful information! :)
For clarification, the earlier links were for LEDs with installed resisters that are soldered to electrical wire and covered with shrink tubing, making it impossible to tell which was the cathode and anode. Perhaps Randy gave the clue. A simple test is to connect the LED with installed resistor to a labeled +/- DC source. If the LED lights, I will know which is the cathode and anode. Correct?
Correct and you can use a 9 volt battery, or a DC power pack.
You may need the installed light pipe for some of your installations. I've cut light pipes to a conveniet length, depending on where I am going to mount the led. I polish the end with #600 wet dry sandpaper. You may need to shield the sides of the led with heat shrink to prevent unwanted light leakage.
I use the same clear caulk for track laying, to glue the led in place in the shell or to the back of the light pipe. If for some reason, you need to remove it, it just pulls off.
Henry
COB Potomac & Northern
Shenandoah Valley
No one mentioned this, but some decoders, like the loksound direct select, already have a resistor on board, so you don't need another one.
Thanks Henry! My GP-30's don't have light pipes. What do you suggest as a replacement? Also, does it matter if it is light tube is mounted horizontally relative to the headlight lens versus at a slight upward angle? For the speaker install, I may need to remove too much chassis to have a horizontal orientation relative to the lens. Hope that makes sense...
Thanks for the heads up on the loksound decoders.
IDRickMy GP-30's don't have light pipes.
hmmm
Go to www.Hoseeker.net and look up Life Like GP30 page 3. #3 there are two of them, front and rear have different shapes. They are wedge shaped pieces of plastic with two projections that serve as the headlight lens. It also is the number board as part of that same part.
I've never had to create a number board. Glueing something to the back of the hole is going to look weird.
For the paired headlights, I have. Find a clear plastic sprue that held windows for some other building kit. Chuck it in a drill and run it across a file until it's close. Use sand paper and the drill to turn it to the correct diameter.
I think you want this pipe to be as close to parallel to the tracks as possible.
Thanks Henry! You got me, I had simply removed the shell and set it aside, which of course, is where the lightbars are located... Thanks for the correction and suggestions! :)
IDRickIs there an accepted uniform color coding that red is always (say +) and black is always (say -)?
Basically, there is but manufacturers are not always inclined to stick with it. Life-Like and BLI frequently use all black wire. I often find red on the minus side of the motor. Check the motor rotation/locomotive direction. When the locomotive moves "forward" you have found the + side of the motor.
NMRA originally set up DC standards so that IF the right rail saw DC+ that would move the locomotive forward. I use a DC power supply (below) but you can check with a 9V. battery if you don't have any other way.
Meter-A by Edmund, on Flickr
Those pre-wired LEDs from WeHonest have black and red leads for — and + respectively. BUT as pointed out, TEST them first. This is the handiest LED tester I've ever seen (can't find them anymore) I think I got mine from Lloy's Toys or Tony's. You could make your own.
IMG_4764_fix by Edmund, on Flickr
IMG_7094_fix by Edmund, on Flickr
I'm using it here to "ring-out" the wiring (all black) to the PC board on this BLI F7. with two number board, a headlight and a Mars light AND a cab light! By sorting these wires out I know what has to go where. This is also a good case of "if it ain't broke" since all the LEDs are on this board right where they have to be to align with the shell. I only changed out the Mars and headlights to a better color. The yellowish number board lights were fine but I upped the resistance to dim them way down. I got rid of the cab light.
IDRick What do you use to hold the LED in place as your final installation step?
That often varies by the locomotive type and how the manufacturer originally set up the headlight housings. Kato is a big user of elaborate "light pipes" so was Bowser sometimes. They would have the LED placed directly on the PC board and direct the light out to where needed. Not always successfully.
Here, I used Kapton tape:
SD_9-decoder-3 by Edmund, on Flickr
The little bit of tape on the side of the weight also helps to reduce vibration noise from the shell walls.
Sometimes I use canopy cement and there are times when I'll use a clear gel-type cement. I avoid any use of "super-glue/ACC" type adhesives. They will fog the clear styrene and sometimes make a mess of the LED, plus you need time to get the LED set just right.
IDRickthere may be a need to mill out the manufacturer's groove for the rear headlight. How do you in attach the LED headlight in this situation and how do you focus the light out the rear headlamp lens?
I try to avoid mounting the LED directly to the shell but there are cases where it is unavoidable. If you search the WeHonest site you'll see pre-wired, two pin mini connectors. For me, these are quick and easy to make the shell removable by unplugging (IF there's room to cram the extra wire under the shell).
Otherwise, I use a caliper or divider to measure where the LED has to be to meet the lens of the headlight and make a bracket out of Evergreen styrene or sprue pieces.
Here, on this BLI RSD-15 I left the LED leads long and pointed them toward the headlight. There was a beveled "sweet spot" on the headlight housing that this LED is aimed for.
BLI_BLE_RS15dcc by Edmund, on Flickr
Here, I have mounted a second LED which is always lit for the number boards. Yes, some light leaks into the headlight area but I have seen this happen on some real engines, too, where lights in the engine room "leak" past the headlight.
Below is a "milled frame" on a Genesis F-3. I placed a big 28mm hi-bass speaker back here in a large enclosure. Since then I have begun using sugar cubes so not so much surgery has to be done.
IMG_2849fix by Edmund, on Flickr
I did this with a small 4" die-grinder and a good, flat mill file.
Hope this helps,
Thanks for your time and effort Ed! Always very helpful and instructive!
A little off-topic maybe, - how would i wire an LED in an F7A so the headlight is always on (no rear lights) - I am guessing that using the blue (with a resistor) and white decoder wires keeps it on going forward; can I
also connect the yellow to the white so it is lit when the engine reverses? or is this (electrically) bad for the decoder? or, run the yellow through a diode to protect the decoder? and maybe add a small resistor to the white connection so it's dimmer when going in reverse? [I admit to being mechanicaaly-inclinde, but electically-declined in nature....]
MrMickA little off-topic maybe, - how would i wire an LED in an F7A so the headlight is always on (no rear lights)
Hi,
Most recent decoders will allow you to choose F0 options so that the headlight will be on in both directions. I did one like that where the headlight was on bright while moving and it dimmed when stopped. Another case I had a switcher that I set up to have both headlights dim in both directions but you could press F7 and the headlight would be bright in the direction of movement and the other one stayed dim.
Look up lighting options for your particular decoder.
In other cases I "hot-wired" LEDs right from the track pickups. Bypassed the decoder alltogether. I sometimes do LEDs for number board lights this way.
Just an LED and a 1.5 to 2.5 K Ω resistor in parallel with the rail pickups.
Thanks, Ed; I like the option to hotwire the LED, and I am already hard wiring the power from the trucks so its an easy approach as I rebuild this BlueBox loco. I have a 2--wire microconnector so I can separate the shell if Ineed to in the future
Hot wiring of course prevents you from ever turning off the headlight. My prototype, for example, didn;t actually use headlights in the daytime in the era I model (I have a rulebook). Most decoders allow you to set teh F0F output (white wire) to be non-directional, so it can be on or off in both forward and reverse. However, in the event that the decoder is not configurable for this, it is perfectly safe th hook both the white and yellow wires to the - side of the LED and the blue wire to the + side (with a resistor in there of course). The way the decoder function 'outputs' work, you can always create an "or" condition by hooking 2 or more function wires to the same light. When you do so, the light will be on if one of the functions is on, or the other is on, or both of them are. I don't think anyone offers the complete freeform mapping of functions to buttons that ESU does, but you can sort of get around it by connecting multiple functions to the same light.
So I have yet to map a function. I will have to dig out the Kalmbach book on this topic and see how difficult it is. But from what you said, i could connect both with a resistor in the Blue wiring, and a smaller resistor in the yelow wire: when the loco backs up, the headlight should dim; am I reading that correctly? alternativley, I will dig inot hte decoder manual for this DH 123 and see if it features Rule 17 lighting, which ( IIRC) will automatically dim the forward head light wehn the loco backs up?
Somewhat - you'd have to play around with the resistor values since the brightness change for the LED goes from mostly full brightness to not visible over a very short range. The logic of wiring that way is sound, and won't fry anything, just might be hard to get the results you want. When a decoder supports dimming an LED, it doesn;t do the same as inserting more resistance in the circuit, it actually blinks the LED very fast and increases the percentages of "off" time which makes the LED appear dimmer. This is the same PWM used to drive the loco's motor. The peak voltage is always the same, but as you increase the amount of "on" time, the apparant voltage rise and the motor turns faster.
This post has been very helpful.
Thank you everyone.
trainmasterg This post has been very helpful. Thank you everyone.
Boy, you're not kidding. I love this forum...(someone already said that...oh yeah,me.)
WP Lives
MrMicki could connect both with a resistor in the Blue wiring, and a smaller resistor in the yelow wire: when the loco backs up, the headlight should dim; am I reading that correctly? alternativley, I will dig inot hte decoder manual for this DH 123 and see if it features Rule 17 lighting, which ( IIRC) will automatically dim the forward head light wehn the loco backs up?
the TCS T1 has CVs for controlling the brightness (CV 15) and dimming (CV 61) depending on direction
greg - Philadelphia & Reading / Reading
Ya it's a lot easier to just use a couple of CVs to get the lighting you want, rather than doing a rat's nest of wires and resistors to do it "automatically". Most all of my engines are set up so both headlights come on when I press F0, with the light in the direction of travel bright and the reverse dim. On some decoders, it only takes a couple of CV settings, on my MRC decoders it only takes changin one CV.
I've also set up F-units with two headlights so that the upper light flashes like a Mars light and the lower one is full brightness when going forward, and the lower light goes dim and the upper stops flashing when going in reverse. Again, just turning it all on and off with F0; set up by changing a couple of CVs.
Resurrecting an old thread that I started...
Finally getting around to buying the LED's for my locomotives. Earlier in this thread, Ed graciously gave me an ebay link to prewired LED's with a 1k resistor. Specs also say for 12 to 16 volt environment. That chinese company no longer has LED's on ebay. I'm having a difficult time matching that spec, several say 12 volts. Prewired with a resistor seems preferable for ease of installation.
However, I'm considering soldering my own, have not done that before, but chance to learn a basic skill. I found a firm that has very reasonable prices for LED and resistors.
https://lighthouseleds.com/3mm-led-warm-white-ultra-bright-16-000-mcd.html
https://lighthouseleds.com/1-4-watt-metal-film-resistors-with-1-tolerance.html
They do sell a prewired 3mm LED but it only has a 580 ohm resistor. 48 cents for a premade versus 28 cents + labor to make my own. I only need 4 so the higher price is not cost prohibitive by any stretch. Is that resistor adequate? The size of the resister depends on the applied voltage, voltage draw of the LED, and desired current level.
Please check my math. The DCC system I'm buying has a 15 volt output and the LED's use 3 volts, and max current is 20 mA (0.020 A). I have read that you want to set the target current at half the max current. Using these specs and ohms law (R=V/I), the desired resistor is:
(15v-3v)/0.010 amps = 1200 ohms
Assuming my calculation is correct, I should make my own since the prewired is only 580 ohms. Randy suggested that I use a TCS-T1 decoder in a different thread and has stated the 3mm LED fit P2K GP30's. I found that TCS sells a T1-LED version that has an onboard resistor and the manuf suggests that no additional external resistors are needed. The Manufacturer does not specify the value of this resistor and has not reply when I emailed Tech support. Any thoughts on the R value of the onboard resistor? Should I just purchase the prewired 3mm LED with 580 ohms resistor and assume the onboard is sufficient to meet the target resistance value?
I have read that sunny white is the preferred LED for modern locomotives. Several suppliers sell a 3 mm LED that is Sunny white for ~$1.50 each. I'm not a rivet counter so was just curious if there is significant difference in appearance to justify for the slightly higher cost LED?
What guage wire should I purchase? What size shrink wrap? I have 63:37 solder with a rosin core. Acceptable for electronics? Is flux needed and if so, what type? What temperature?
Thanks!
As to appearance - there is a definite difference. An old seller who is no longer around used to have a comparison picture with three of the same loco, one with golden white, one with sunny white, and one with bright white LEDs. Big difference. Sunny White is good for a modern loco, I am pretty much all first gen diesel so I only use the golden white ones.
Soldering your own is a worthwhile skill. You have the right solder - depending on the diameter. You want some thin diameter solder for fine wires and electronics, I use .015 diameter rosin core 63/37. I don't use extra flux with decoder installs. For decoders and the fine wires associateds with them, if you don't want to invest in a soldering station yet (which at around $50 for a good one isn't a huge investment), you want no more than a 15 watt iron.
Several vendors sell bundles of decoder wire, the same wire that comes on the decoder harnessed. Get some of this, and maintain the color code - ie, if you need to make the blue wire longer, use more blue wire, not another color. And when you cut extra wires off - ones you didn't need to hook to anything, save the leftover sections.
Your resistor calculation is correct, but 1K is fine - if you solve for amps and put 1K in, you get 12mA, still well within the safe zone for the LED. The resistors included in the TCS LED decoders, I'm not sure of the value, but they limit the current to well under the 20mA limit.
The decoder wire is around a #30 wire. You need some pretty small shrink wrap - places that sell decoders often have the right size, otherwise the typical assortments you get has a whole bunch that is far too large and not much of the really small stuff. I usually solder my resistor right to the LED, cutting the leads of both short. Make a good mechanical connection, then it should only take a second with the soldering iron. When doing it that way, you can't put the heat shrink on first, but the smallest size that just barely fits over the resistor will shrink enough around the solder joint behind the LED. For the wire with no resistor in it - don;t forget to slip the heat shrink on FIRST, then solder the wire to the LED. Same with the free end of the resistor.
Heat shrink, I think I use 1/16" and 3/32" The only local retail store you might find this is a Microcenter computer stores. Mail order, the usual DCC stores and electrical supply stores have it or an assortment of by Soundtrax
I have had an intention tremor my entire life and lately it has gotten worse. I use helping hands: alligator clips on moveable arms. I position the shorted led lead and the resistor lead parallel and touching and overlapping. I tin both leads beforehand.
If all you are doing is adding LED's I suppose any color is OK, I bought the collection of DCC colors from one of the above stores. 30 ga you can strip the insulation with your fingernails.
Thank you, Randy and Henry! Excellent advice, always very helpful!
Best,
Rick
I heard back from TCS, the T1 LED decoder has a 1k resistor on board. Awesome!