LED MARS light- how to fabricate the components

I use the ngineering ones when I need a MARS light.  In one of the diesel units I installed it in, I powered it from the headlight circuit and used my motor sensing circuit to know when the locomotive was moving.  The MARS light should only run when you're moving, that's why I used the sensing module.  I've installed a couple for other folks as well, and one is in my RailKing Imperial FEF with a red lens very cool looking and prototypical for the 844.

I haven't done any of mars lights as a stand-alone unit as I could never offer them for what you can buy the ngineering ones for.  I may build that functionality into a larger module for diesels that has multiple functions, ditch lights, MARS, Rule-17, and cab light control.

I rolled my own P/S for the MARS simulator, just a diode, cap, and a 5V regulator.  That works fine for the TMCC headlight output.  For DCS, I cheated and tapped voltage off the headlight and filtered that for the power for the module.

So all I need to tap the headlight is the Diode and cap since I have DCS.  and then run the power and ground to that module.  then run the leads from module to the Mars LED.  what size LED should I use to fit in the GS4? I don't have any on hand right now to try.  you used

what size Cap and Diode do you need to use?  I bought a bunch when I did the flickering LED firebox circuits.  I have a good iron that is variable temp, so I can be real careful on this tiny circuit.   did you ever draw up a diagram for DCS setup for one of these mars lights.  I still have the one from the flickering one

I'd use a 220 ohm resistor, then the cap, and finally an LM78L05 regulator to drive the board.  No diode really needed here, the lighting outputs are pulsed DC and don't change polarity.  I just add the resistor as sort of a current limiter, and also so that we don't put a capacitive load on the lighting circuit.  Make sure you locate the + lead on the lights, if you follow it back it's the purple PV lead.

I never actually drew a diagram as it's simple enough that I just wire it.  The one for the flickering firebox was drawn in response to a query here at OGR.

Important note!  You do not ground ANYTHING in the PS2/PS3 environment to frame ground, the negative side of the headlight is the "ground" for this circuit.

what is the cap that you use?  I have some I used on the flickering setups.   maybe I have the one I need.  ill order up the regulator and the Led's. 

DO you think I can split off the power from the headlight and also run cab and flickering firebox in addition to the headlight and MARS and markers? 

thanks John.! 

For the little MARS light simulator on the MTH power output, you can use a pretty small cap, say 22uf at 50V would be a good choice.  The MTH has marker light outputs that directly drive LED's, why not use those?  The headlight will drive three 60ma bulbs, that's done in several factory installations.  So, unless you go crazy with something here, you can easily drive three set of LED's.  If you're driving more stuff, kick the capacitor up to maybe 100uf 50V.

this GS4 originally had nothing! no cab figures, no lights other than the headlight. but I wondered with the new PS-2 setup. is wiring in the engine now for having the markers, cab and firebox that you can control with remote?  interior on/off  markers on/off?  headlight on/off.  I bet they don't have Mars setup though on/off.  that would be cool if you could set that up.  but I guess like you said you can drive that off the engine power to turn on when its moving. 

thanks a bunch!

Chris

Driving off motor power isn't quite as simple as it sounds, but it can be done.  This is the module I built to do that.  I have entertained the idea of making a PCB with this logic on it, but that hasn't happened yet.  I also use this module for Rule-17 lighting and cab light control.