Easy Directional Leds for Diesels or Electrics

Thought I would add the board gerbers and recently updated user notes pdf just to make them easier to find.

Rod

@Rod Stewart Would these work?

2mm Bi Color Leds (10 pack) $1.30 note minimum order is $5

Steve those look like they should work just fine. Good find. I went ahead and ordered a few so we’ll see how it works out. Thanks!

Rod

Well I received the bi-color 2mm leds from LED-Switch, and they work great! Check out the video below. And these are a great size for trains representing a scale light about 4" diameter.

Rod

Glad they worked out 🙂

Sounds like a fun project, but why would you want green lights on the front of an engine moving forward? I understand red marker lights if the engine is on the rear of a train.

Yes Steve, they work quite well. And the green tends to be a much richer shade of green than many of the wimpy green leds available out there. I really like them. The video clip does not do them justice.

For the testing what I used is a small DPDT toggle switch to alternate the polarity quickly to both sets of leds. Installed in an engine, when in neutral neither set of leds would be lit at all if they are powered by the +/- supplied to the motor of course. Using 470R load resistors I found the leds are weakly lit at 5.5 volts, and nice and bright by about 7 volts. There is not much noticeable change in intensity from about 8 volts up to 12 or so.

A better way to smooth out the variable intensity would maybe be to replace the load resistor with a CL2N3 controller soldered into the same pads. Theoretically then the leds would be at 20ma current as soon as the voltage exceeds the total Vf. May have to give that a try and see what happens. Clearly the CL2N3 would be the most expensive component on the board!

Uh-oh, I just realized the CL2N3 might not like reversing polarity, so that idea is out I guess. Ho-hum.

@Magicland posted:

Sounds like a fun project, but why would you want green lights on the front of an engine moving forward? I understand red marker lights if the engine is on the rear of a train.

Oh I don't know, just for fun I guess! And because we can.

@Magicland posted:

Sounds like a fun project, but why would you want green lights on the front of an engine moving forward? I understand red marker lights if the engine is on the rear of a train.

Colored lights did have a purpose...

White. Indicated an “extra” train not shown in the timetable. For much of railroad history, train-movement authority was granted by timetables. If a train was listed in the timetable, it had the authority to operate according to its printed schedule. Deviations from the timetable, such as a train running late, were handled with train orders from the dispatcher. Under this “timetable-and-train-order” system, it was important that trains kept as close to schedule as possible, and that any special trains not shown in the timetable be clearly identified as such with a white light. Many freight trains operated as extras, and thus carried a white classification signal.

Green. Indicated that, while the train displaying the lights was a regularly scheduled one, a second section was following behind it. This was done, for example, when ridership demand exceeded the capacity of a single passenger train. If there were too many passengers for a single section of, say, New York Central’s 20th Century Limited, a second section was operated, and, if needed, a third, fourth, fifth, and even sixth. The engine of each section except the last would display green lights. While each section was a separate entity, the timetable’s “train 25” would not be considered to have passed a given point until the last section of the train had gone by. For operational convenience, special trains that otherwise might have carried white “extra” signals were sometimes operated as advance or second sections of regular, but unrelated, trains.

Red. Indicated the end of a train. A train, be it a single engine, a group of engines, or an engine(s) with cars, must have a marker on the rear end. In the (relatively rare) situations when the last element in a train would be a locomotive, the red lights would be lit.

Classification lights phased out

The timetable-and-train-order system has been replaced by other forms of movement authority, and classification lights are no longer used, although older locomotives still have them.

I decided to play with the CL2N3 drivers to see if there is any advantage to using them. Here's the circuit:

The 1N4007 diodes are added to block the reverse polarity. So one set of CL2N3 plus 1N4007 drives the red, and the other side drives the green. I initially had the leds in series but the required voltage to make them bright was too high, so parallel leds got the nod. The minimum required voltages to reach steady intensity are 6.5 and 7.5 for red/green respectively using this setup. Higher voltages right up to 24vdc don't affect brightness. I experimented removing one 1N4007 diode, and poof! Splash two leds, which I kind of expected. The CL2N3's both survived though.

The real question is; for a typical two can motor diesel, what is the needed voltage for them to start moving?? Anyone know? If its much less than the voltages above, the leds are still going to vary in brightness, which might not be good.

Rod

When I check out an engine before installing a control system, I test the can motors to determine start voltage and direction polarity. In most cases a DC voltage of 3 to 5 volts will start the motors rotating.

@BOB WALKER posted:

When I check out an engine before installing a control system, I test the can motors to determine start voltage and direction polarity. In most cases a DC voltage of 3 to 5 volts will start the motors rotating.

Great thanks Bob, good to know. So I am thinking that with engine on track and a bit of a load, starting voltages should be 5V+. So the led starting voltages with the CL2N3 might not look too bad. A bit of experimenting once we get home should tell the tale.

First off, the CL2 want's filtered DC, so that will be one problem with the hash that comes from the motor.

Have you tried the bi-color 2-pin LED directly from the motor with a 470 ohm resistor?  You might be surprised at how well that works.

Here's a simple test with a bi-color LED and a 470K resistor.  I cracked the throttle until the motor just started moving at first, note this is a bare motor with nothing holding it back.  Then I cranked it up a bit and finally reversed it and repeated the steps.  Yes, it gets brighter with speed, but not as much as you might think.

@gunrunnerjohn posted:

First off, the CL2 want's filtered DC, so that will be one problem with the hash that comes from the motor.

Have you tried the bi-color 2-pin LED directly from the motor with a 470 ohm resistor?  You might be surprised at how well that works.

I have not tried that yet, looks like it may work just fine from the video clip in your later post. Thanks!

One benefit of not having any other devices in series with the LED is you get a lower voltage startup.  The nice thing about the two-pin bi-color LED's is the have internal reverse polarity protection based on the two LED chips.  Sometimes the K.I.S.S principle works out best.

@gunrunnerjohn posted:

One benefit of not having any other devices in series with the LED is you get a lower voltage startup.  The nice thing about the two-pin bi-color LED's is the have internal reverse polarity protection based on the two LED chips.  Sometimes the K.I.S.S principle works out best.

Yes we are on the same page John. The idea of trying CL2N3's was to see if they offer any great advantage over the KISS approach. The advantage is that from about 7.5 volts up there is no change in LED intensity because the drivers are controlling the current. The downside is the two blocker diodes add to the required start up voltage making it around 6.5 volts. Plus more complexity and cost. Not good. And I proved the blocker diodes are essential.

In the end I will likely go with a resistor and two LEDs in parallel. I modded one of my 2mm class marker led boards to put the leds in parallel, just for testing. Playing with that a bit I found a startup voltage of about 5.4 gives pretty good intensity. So now I want to test that with a can motor and see if we are in the ballpark.  I figure the typical engine can motor voltage range would likely be from about 5vdc (as Bob said) up to about 10vdc. So that's the sweet spot. Research continues.

Truthfully, from 7.5 volts on the motor and up, it's pretty hard to see any difference in the intensity of the LED's just connected directly across the motor.

So after some testing with 2 parallel bi-color leds with a 470R resister and an unloaded 12vdc can motor, here are some results. (The test motor is about 1-3/8" diam x 2" long and quite heavy. Its resistance is about 5.2 ohms. It's manufacturer is not known but it's not a Mabuchi or any other common train motor.):

2.2vdc: Red leds steady but dim; motor just turning over. Green leds behaved same but needed 2.8vdc.

4.0vdc: Both colors fairly bright, motor running faster.

6.0vdc: Both colors comfortably nice and bright.

8.0 and 10.0vdc: No change in brightness to speak of.

When the voltage is reduced both colors dim noticeably below 5vdc.

This is all highly subjective of course, but in conclusion it looks like voltage levels above 6 or 7vdc will produce acceptable brightness, which agrees pretty well with grj's assessment above. Next step will be some actual engine testing. Since this board is exactly the same in size etc as the class led board put in my Soo Line MP15 switcher a year or so back, that will be the easy to mod test bed! More to follow.......

I think you'll find in real practice that getting the locomotive running the markers will be sufficiently bright.  Don't let perfect be the enemy of good here.

So I received the R1.21 directional led boards, and they work just fine, Here is the board layout and a test picture:

Note this pcb has provision to use either a fixed 1/4W resistor, or a 3362P style trim pot. With the pot you can dial in the led intensity that you like best. A 500R or 1K pot would be good choices. As with the earlier testing above, reversing the polarity to the board switches the red leds to green. It's important to note that you must be cautious turning up the juice to the leds otherwise they will go poof if you get too aggressive. An ammeter inline as you make adjustments would be a good idea. The gerbers are attached below for any who wish to order their own. I also have a few spare that I can sell; shoot me an email if interested.

Rod

Here attached is a pdf of some user notes for this board that should make using it a bit easier!