Replacing MTH headlight with LEDs

Check this recent thread.

Contact Evans and ask them.  I don't think you'll be the first to ask. 

The PS2 incandescent signals are pulsed-DC which can reach 20V or so.  Apparently some Evans LEDs include a capacitor that helps with flickering.  They would know how it behaves with the PS2 signal.  Let us know what you find out!

Well after rereading the 'recent thread' it looks like Evans Designs LEDs are set for 9-18 volts which means track power.  I need to know how many LEDs can be run off a PS2 upgrade board(3V) with just one connection for a headlight.  If I use the ED LEDs it looks like they would be extremely dim if run off the board and not track power.  

So if I purchase 3-5V LEDs can 3 of these be run from the one connection for the headlight from the PS2(steam engine upgrade kit) 3V board?   Looks like I will have to add my own resistors too. 

I was hoping Dale H. would chime in, his knowledge seems to be all encompassing on things electrical!

There must be someone out there who has done this modification.  Thanks in advance.  I find this forum an absolutely amazing source of information.  

You may have problems with white LED's running off the board if it's really putting out 3 volts.  White LED's typically have an operating voltage of 3 volts, and much below that they simply turn off.

Have you considered running them off track power with a diode and resistor?

After more research and thought, I think I will run the firebox glow and marker lights off track power(2 new LEDs) as suggested by gunrunnerjohn and maybe change the MTH headlight bulb to an LED.  I don't want the headlight running off of track power.  Thanks for the ideas. 

Off to AZ tomorrow so it will be a while until I get back to this.  There is an outdoor Garden Railway Tour on the 10th and 11th in Tucson!   Going to cruise over to that. 

I've used some external logic to do stuff with lights that I wanted to control using the command/control outputs.  Perhaps you'll need to consider a similar thing if the voltage from the MTH board isn't up to the task.

John, 3V in PS2-3V refers to the voltage used by the digital processor; PS2-5V boards use a 5V processor.  PS2 incandescent bulbs are 6V so adequate voltage is available to drive LEDs; it's the type of signal (high voltage pulsed-DC) that requires consideration. The pulsing varies to maintain constant brightness across a resistive filament. As you know, LED brightness is proportional to current which represents a different type of load to the PS2 circuit. 

Makes sense.  But out of curiousity, did your research determine that you can't tap into the PS2 outputs for Marker lights and Firebox glow?  That is, the hardware is there to drive those signals.  It's "just" a matter of finding a soundset to download that enables these signals but I'd think that knowledge is out there (perhaps in the PS2 forum).

If I'm not mistaken, the PS2 Marker outputs are meant to drive LEDs so they would be directly compatible - no resistor required.  You'd need to find a few crimped wires that snap into the unused positions in the harness connector housing. 

I have not installed a PS2 upgrade kit so I may have an overly simplistic view of the matter.

I know about the PS-2 battery voltages, just didn't realize that was what was being referred to.

The high voltage pulsing I think I'd deal with with a cap across the LED.  With the series resistor, that should smooth things out.  If it's really severe, I guess diode protection might be called for.  I wonder if anyone has a 'scope picture of that this looks like?

I've never tried to add lights to PS-2 locomotives, though I have on in the closet that I'm going to be looking at sometime.  Maybe I'll have a better idea how to add them then.  Now, ask me how to add lights to TMCC locomotives, I'm your man.

Stan,  The PS2 upgrade kit does not contain leads for marker lights and firebox glow.  My initial mistake when I installed it was I believe I removed a constant voltage board that controlled these lights in the RK M1 Mountain Locosound engine that I converted.  Did not know enough of what I was doing!   I assumed it was the Locosound board since there was nothing in the tender but the speaker and battery.  So any additional lights are going to have to come from track power or from the board powered headlight or maybe even smoke unit fan.  That is why I think I will just use track power for those two LEDs when I install them, if I have room for the wiring etc and can best figure out how to locate everything.

That ‘recent thread’ was just updated suggesting an Evans LED solution for the headlight.

Perhaps there are different flavors of upgrade kits, but the PS2 steam kit on the MTH site says it includes 2 Marker LEDs (tender-side) with wiring.  So if yours did not come with it, perhaps you can separately buy just the Marker assembly from MTH.

Re the firebox, if your model has a red/orange lens, white or warm-white LEDs are not “rich” in red/orange light content relative to an incandescent for back-lighting thru a colored filter.  Some experimentation may be required to select LED color between white, red, orange, or perhaps some combination.  If going for the active firebox effect, I see Evans (and others) have flickering LEDs too.

Stan, the tender harness has marker lights but not the engine harness.  If you could get the wires up to the engine maybe that would work.  But I don't believe you can do it within the bounds of the 10 pin engine connector.  The other question is basically my first question.  Could I run 4 marker lights off that tender connection designed to run just two?   

I think I will leave the headlight alone and run the marker lights and firebox glow off of track power.  That seems to be the easiest solution. 

Could you live with half the brightness?  The two marker LEDs in the tender are supplied by a fixed current circuit.  You could splice in an additional two marker LEDs as long as they are not white LEDs (which require higher voltage).  So if you're doing two pairs of red-amber markers it could be done with a little re-wiring but no new resistors. I know it's hard to visualize what half the brightness will be in an LED but it's not as bad as you might think and probably worth the tradeoff if you want the additional lights.

You could run them off track power, but use a CL2 constant current chip to give you fixed intensity.  I don't recommend paralleling LED's, sometimes one is a lot brighter than the other, and in extreme cases, one may not light at all.

Since this thread is alive again I'll throw in my 2 cents worth.

While I am sure that Dale's circuit would work fine for running the headlight LED off track power, I would leave it as is for 2 reasons.

One, you won't be able to turn the headlight on and off from the DCS handheld.

Two, if you ever run conventional, the headlight will be very dim.

If you are adding boiler marker LED's, I usually add these to the headlight circuit, using the MTH green marker LED harness. This has the two LED's wired in series. I also add a 390 ohm 1/8 watt resistor in series to set the current limit right.

Done this way the marker LED's turn on/off with the headlight.

If it's tender LED's you want, Stan's suggestion is the easiest way to go.

Rod

If using the Cl2-N3 chip ,the the lighting is constant voltage.

Point taken Dale; thanks for the clarification.

Do you have a link to the data sheet for teh CL2-N3 chip by chance? I could not seem to find it using a Google search, and I am unfamiliar with it.

Thanks,

Rod

Here you go, a place to order it and also a link to the data sheet.

CL2N3-G

Thanks John

Rod

Hi Rod,

Do the 2 series marker LEDs (plus 390) change intensity with track voltage?  I'd think they would but perhaps it's so slight as to be negligible.  That would be good.

Stan;

No the circuit is a constant voltage 5 VDC circuit. The PS-2 headlight, and consequently the marker LED's, all run at constant intensity, in DCS or conventional mode.

Rod

MTH service could not adequately answer why this is done.  There are various configurations over the years.  Something about stability, for what ever that is worth.  G

I'm certainly no electronic wiz kid and I did mess up a board one time trying to add lights to a PS-2 engine. I use Evans LED's off the rollers now with no problems. Whatever lights I'm using don't go off when the engine shuts down but that's not a deal breaker for me considering the lighting affects I get. 

I've never had any issue with the LED's from the MTH incandescent outputs just using a 220 ohm resistor in series with the LED.  For dual LED's, being the lazy type, I normally put two in parallel and use a 150 ohm resistor.  They operate nice and bright and turn off as they should.

The Marker 1 and 2 outputs drive LEDs and current-sources putting out something like 10 mA.  Not that one can design a pure current source but current sources in theory have infinite impedance so even if shorted the wasted energy would be limited.  I never heard the "stability" reasoning that GGG mentions but taken at face value, then why not turn lemon into lemonade - break the loop in pin 6-8 and install an LED(s) of your choice to light up something else in your engine and maintain that stability.  Of course it would go on/off under LMK softkey control.