I'm installing a TCS M1P decoder in a Atlas Master Series S-2 switcher. It comes with an 8-pin plug, which I removed and installed the decoder.
Am I correct to assume that, if the wiring diagram only shows incandescent bulbs for the headlights, I will need to add resisistors in order not to blow the LEDs? Neither the decoder manual nor the locomotive box indicates anything otherwise.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
Of course all the installation pictures are the old ones, like the one I have that was the one diamond in the rough in a box of mostly junk I bought cheap.
If the stock loco has bulbs, then you definitely will need resistors. However - this is the tricky part. You'll have to trace the wiring back to see if they are wired directly across the track pickups (maybe with a diode if there are directional lights) meaining they are full 12-14V bulbs so you will get full decoder output at the light connections on the factory boards. Or maybe they are wired across a string of diodes like P2K locos, meaning they are maybe 3V bulbs Or they are wired across one two diodes and they are 1.5V bulbs. Or there is a Big Honking Resistor (that's a technical term) on the factory board to drop power for the lights, usually those sort are the type that have jumpers to cut for DCC installation.
Or, put the M1P to 8 pin harness away for another loco and just hard wire the M1P to the pickups and motor and lights - you KNOW you need resistors in that case, and exactly what value they should be.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Randy,
This Atlas S-2 comes with LEDs and it appears that it has been wired for them.
I held the circuit board up to a bright light. One of the front LED traces (w/attached red wire) goes through a 1K (102) SMD resistor and one of the rear LED traces (w/attached red wire) goes through another 1K resistor. Each of those traces then goes through it's own diode.
Does that sound like a safe bet that I can just put the locomotive on the programming track and not have the LEDs blow? I do have spares if it does.
V=IR12 = I *100012/1000 = I.012A = II'd guess the LEDs should be fine on 12 milliamps.
Disclaimer: This post may contain humor, sarcasm, and/or flatulence.
Michael Mornard
Bringing the North Woods to South Dakota!
Well, I took the plunge and placed the S-2 on the programming track. The LEDs lit up - just like they're supposed to.
I'm kinda disappointed with Atlas in the alignment of the LED through the front headlight lens. It's not even close - ~1/8" too high, easy. To remedy that I'm replacing the front LED that came with the locomotive with a 3mm Miniatronics Yeloglo LED that I've put two extremely short opposing 90-degree bends in. That will allow the LED to bend over the front of the chassis and down; bringing it closer in alignment with the lens. It still won't be perfect but it will definitely be an improvement.
I'll try and post pictures tomorrow night after I solder the wires onto the new LED. If that doesn't work then I'll probably try a SMD warm LED on the front of the chassis. Given the small space between the chassis and shell, that would be the ideal LED to use.
Hi Tom:
I now use 0603 SMD LEDs for almost all locomotive lighting. If you don't like soldering your own leads to them the prices for pre-wired ones are getting better all the time.
The reason I have gone to the 0603s is that I can position them very accurately behind the lens. I use 90 second epoxy, and I apply power to the LED when I am installing them. That allows me to see exactly how the light is coming through the lens. Often, only a very tiny repositioning is required to make the difference between good light projection and bad lighting.
One thing to be aware of with the epoxy is that the LED can still move slightly even after the epoxy seems to have set. If you can put a dent in the epoxy with a screwdriver tip the LED can still move. I make sure the epoxy is hard before letting go of the LED.
Another reason for using 0603s is that they take up almost no room which can be advantageous where space is tight.
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
Well, it looks like the SMD LEDs are going to be the way to go with this locomotive.
I got the prebent LED as low over the front of the chassis as possible. Unfortunately, it was still a 1/2 an LED too high in the lens and the LED stuck out too far; leaving a 1/32-1/16" gap between the shell and the front of the cab when everything was assembled back together. I knew it might be a stretch but wanted to try anyhow.
Dave, where to you purchase your SMD LEDs from? eBay? Also, does the thickness of the SMD LEDs change much with the size? I was just wondering what the difference in thickness was between a 0603 and 1206, besides being twice as large L x W?
Hi again Tom:
I get my SMD LEDs from eBay. I don't have a preferred supplier but 'wehonest' seems to be pretty reliable. Usually I just go by price.
I am not familiar with 1206 LEDs. I have used a few larger LEDs to try and get more even light distribution for number boards (two LEDs side by side). The LEDs I used measure .13" x .12" x .07" thick(dimensions corrected thanks to Randy Rinkers exceptional editing skills) so they are quite a bit thicker than the 0603s which are about .02" thick. I don't know what the official size designation is for the larger ones.
I also don't see a reason for using anything larger than 0603s, except in cases like the number boards mentioned above. The 0603s are plenty bright enough IMO. 0402s are bright enough too, but they are so small I find them to be a nuisance to work with. I have soldered my own leads to 0402s but it is more trouble than it is worth. For the quantities I need I can afford to buy the pre-wired ones.
One suggestion I will make is to get yourself some different coloured paint pens. Many pre-wired LEDs do not have colour coded leads. Polarity is indicated by the positive lead being longer than the negative lead. That's fine until you have to clip the leads. I use the paint pens to mark the leads. The reason for having a selection of paint pens is so you can mark the various negative leads to show which function that lead should be hooked up to. For example, white for headlight, yellow for back up light, green and purple for ditch lights, brown for number boards etc. etc. All the unpainted wires go to the blue common lead on the decoder.
While I'm offering advice, don't cut the decoder wires too short. Having the decoder wires too short makes it difficult to separate the shell from the frame, and if you need to replace an LED you want to have enough wire to work with. The extra wire can be taped inside the shell.
If yoou really mean .013 x .012, those are actually WAY smaller than an 0402 - the numbers are approximately the hundredth of an inch for length and width, so an 0402 is .04" x .02". As 1206 would be .12" x .06", it sounds like the ones you use might be 1210's, which are supposed to be around .12" x .1" (the sizes are a few thou larger than nominal, ie in the 12xx series they are usually .126").
And then to confuse everyone, there are the metric sizes in tenths of a millimeter, which ARE exact, and have overlap - there is a METRIC 0402 which is much smaller than the Imperial 0402. Most of what you buy would probably be in metric sizes since all these things are made in China anymore. 0603 (metric) are the size resistors I use for resistor wheelsets. Not sure I'd want to try to solder wires on them, even with the finest tip I have on my soldering iron. Gluing them to an axle and painting conductive paint works fine though.
In LED strips they often use 3216 or 5050 LEDs, the 216 are the same size as the 1206, and the 5050's are relatively large, at 5mmx5mm.
Scroll down to the "Packages" section here and there is a chart of the zies. It would be odd for there to be a part in a size not on this list: https://en.wikipedia.org/wiki/Surface-mount_technology
Randy:
I guess I got the numbers wrong. One too many zeros. I'll correct the post.
Thanks
Hi Dave,
I can't remember if it was you or someone else I was having a conversation with about mounting LEDs. You mentioned earlier in the thread about using epoxy to mount some SMT LEDs in your locomotives. I just finished installing a 1206 SMT warm-white LED headlight in a Atlas S-2 switcher using 1/16" thick 3M foam tape: (Click photo to enlarge)
The tape holds the SMT LED quite well and it was the only way for me to get an LED low enough in the nose to shine through the front headlight lens (not installed), as mentioned earlier in the thread:
Here it is with the headlight on - Front view and oblique view:
It did require me to unsolder and re-solder the wires (that came with the SMT LED) to the front side of the tabs so that the back of the LED would sit flat against the foam tape. I also bent the LED wires after soldering it on the LED so that it would keep a low-profile inside the shell.
I lightly pressed the LED into the foam tape and positioned and repositioned the LED until I could confirm its proper location through the headlight lens. Once I was happy with its location, I removed the hood and pressed the SMT LED headlight firmly into the foam. I'm expecting it to hold up well.
The rear LED headlight was fine, as is. Atlas added individual connectors for each of the LED wires so you could easily and conveniently disconnect them and the cab from the hood. I don't know what they were thinking with the original front headlight set up. A regular LED just doesn't work.
Edit: Never mind. I see it's been answered. Nice install job Tom. I like those little road switchers. They are fun to run and easy to track.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
It's got a nice big round hole a 3mm LED should work fine. That they chose not to line it up properly is a different story. The SMD LED works great, I probbaly would have just ground a bit off the front edge of the frame to tilt the LED down enough to make it line up.
Like the ones in the Bowser Baldwins with their odd bends - mine had orange LEDs and I replaced them with YeloGlo by carefully copying the exact bends on them - the headlight was easy, but the reverse light up in the cab roof had several bends. They just make contact with copper tabs off the circuit board so there are no wires to interfere with removing the shell.
rrinker Like the ones in the Bowser Baldwins with their odd bends - mine had orange LEDs and I replaced them with YeloGlo by carefully copying the exact bends on them - the headlight was easy, but the reverse light up in the cab roof had several bends. They just make contact with copper tabs off the circuit board so there are no wires to interfere with removing the shell. --Randy
I did the same with my VO-660 and VO-1000 switchers, Randy. Like you, I copied both the front and rear LEDs bends and the contacts lined up just fine.
I actually like that feature in the Bower switchers. It's less cluttered under the hood.
tstage Hi Dave, I can't remember if it was you or someone else I was having a conversation with about mounting LEDs. You mentioned earlier in the thread about using epoxy to mount some SMT LEDs in your locomotives. I just finished installing a 1206 SMT warm-white LED headlight in a Atlas S-2 switcher using 1/16" thick 3M foam tape: (Click photo to enlarge) The tape holds the SMT LED quite well and it was the only way for me to get an LED low enough in the nose to shine through the front headlight lens (not installed), as mentioned earlier in the thread: Here it is with the headlight on - Front view and oblique view: It did require me to unsolder and re-solder the wires (that came with the SMT LED) to the front side of the tabs so that the back of the LED would sit flat against the foam tape. I also bent the LED wires after soldering it on the LED so that it would keep a low-profile inside the shell. I lightly pressed the LED into the foam tape and positioned and repositioned the LED until I could confirm its proper location through the headlight lens. Once I was happy with its location, I removed the hood and pressed the SMT LED headlight firmly into the foam. I'm expecting it to hold up well. The rear LED headlight was fine, as is. Atlas added individual connectors for each of the LED wires so you could easily and conveniently disconnect them and the cab from the hood. I don't know what they were thinking with the original front headlight set up. A regular LED just doesn't work. Tom
Hey Tom!
I usually epoxy the LEDs to the headlight lens in the shell as opposed to the frame, but yours is a very clean installation. You lined the LED up perfectly. I'll have to keep the foam tape in mind when doing future installations. It certainly makes removing and installing the shell a lot less of a hassle.
I am also in the habit of using 0402 or 0603 LEDs which are fussy to handle and get the face of the LED pointed in the right direction. I'll have to invest in some larger LEDs.