MM 201 control front/rear lights individually

[murphaph]

Is it actually possible to configure a Loksound/Lokpilot V4 equipped 201 to allow the rear marker lights off when the loco is hauling something?

I tried (using Lokprogrammer) to add a condition to the rear lights function so that it also requires F22 to not be set but it switches both front and rear marker lights off.

Are the lights hard wired to display the opposite at each end or can individual control be achieved without hardware side changes?

[Noel]

7 minutes ago, murphaph said:

Is it actually possible to configure a Loksound/Lokpilot V4 equipped 201 to allow the rear marker lights off when the loco is hauling something?

I tried (using Lokprogrammer) to add a condition to the rear lights function so that it also requires F22 to not be set but it switches both front and rear marker lights off.

Are the lights hard wired to display the opposite at each end or can individual control be achieved without hardware side changes?

Welcome to the world of function mapping. LokProgrammer is not actually needed for this, it can be done with complex series of CV settings, JMRI may make this slightly less tedious, but there is a very steep learning curve and a lot of time needed to experiment with all of this function mapping of lights. I gave up years ago, it was just too much hassle. Good luck though sounds like a challenge you might like.

 

Edited August 17, 2020 by Noel

[irishthump]

I wouldn't even attempt this  tweak without using the Lokprogrammer! Yes, you can do it with CV's but the Loksound and Lokpilot use indexed CV's which need to other values adjusted before you can change any CV's above no. 255. If you don't set the correct index you can put the decoder in a tailspin!

I 'd have to check but I don't think the 201's front and back marker lights can be set independently of each other. Is there a switch on the 201 for turning marker lights off while in analogue mode?

[murphaph]

So I took a closer look inside. The LEDs are hardwired together from pins 7 and 8 of the decoder, ie when pin 7 is pulled low, the white marker lights at end A go on while the red marker lights at end B go on. 

There is a spdt switch under the loco which allows the path from the red led (led3 according to the silkscreen) to the positive common on the decoder to be interrupted, leaving the red led off.

Helpfully, not, the led silkscreen has the incorrect polarity for those 3 LEDs and it took me a while to figure that out. The cathode chamfer on the larger white LEDs is not visible unless under magnification. I trusted the silkscreen.

[Ross]

Theres a switch under one of the bogies to turn off the red lights 

[irishthump]

12 minutes ago, murphaph said:

So I took a closer look inside. The LEDs are hardwired together from pins 7 and 8 of the decoder, ie when pin 7 is pulled low, the white marker lights at end A go on while the red marker lights at end B go on. 

There is a spdt switch under the loco which allows the path from the red led (led3 according to the silkscreen) to the positive common on the decoder to be interrupted, leaving the red led off.

Helpfully, not, the led silkscreen has the incorrect polarity for those 3 LEDs and it took me a while to figure that out. The cathode chamfer on the larger white LEDs is not visible unless under magnification. I trusted the silkscreen.

Yeah I thought that was the case. The only option is to use the switch to disable the red marker lights. Unless you want to rewire.....

[murphaph]

Yep that's the long and short of it. Hardware changes are required for this. Manually operating the switch with a hundred quid decoder with spare outputs is not an option lol. I don't want the red lights off all the time. They look too nice for that.

 

[murphaph]

I may as well add some information for anyone interested in the 201 electronics.

The main board accepts a 21 pin MTC decoder.

I suspect the majority of owners will have a Loksound 4 or Lokpilot 4 installed as these are the chips sold by MM. These chips have forward/reverse lights, auxiliary outputs 1 and 2 which are wired to the headlights front and rear on the 201 and auxiliary outputs 3 and 4 which are wired (via a pair of transistors to amplify the output because the decoder output is TTL, very low power. The NEM 660 standard requires this but I suspect it was a fake standard created by the decoder manufacturers to allow them to sell you extra hardware later on to actually use these outputs)

An examination of the main board in conjunction with reading the ESU manual for the v4 revealed:

-all function outputs are open collector type. That means the output is switched to the internal gnd of the chip when active. The "return" path is to a common positive pin (pin 5). This is irrelevant for incandescent bulbs but not so for LEDs for example.

-the outermost groups of 4 wires lead fairly obviously to the 3 LEDs at each end of the loco, red and white marker lights and the headlight.

-the red marker led return path to the common positive of the decoder passes through the aforementioned spdt switch, which simply allows the return path to be interrupted and thus prevent the LEDs from illuminating. 

-the two outer pairs of a group of 3 smd resistors on the main board are just the series resistors protecting the aforementioned LEDs from over current.

-the two transistors (marked Q) are used to boost that TTL output from aux 3/4 to a usable level to drive something, in this case they are feeding into the two white headers and in operation on to the cab lights at either end.

This means that all the available aux outputs on a Loksound 4 are exhausted already and without sacrificing one of the existing functions, nothing else can be driven by this decoder.

ESU do offer an adapter board which gives physical access to the "missing" microcontroller outputs. Essentially the microcontroller on the decoder has more outputs but they are not connected to the 21 pin connector. To use them you need that ESU adapter. Neat sales trick but other decoder manufacturers were not as stingy as ESU so it seems that to compete, ESU dropped this approach with the v5 as that decoder has like 10 physical outputs.

I have decided to cease purchasing V4 decoders because of this limitation. Luckily I only bought one. For that one I'll consider putting it in a ballast plough with ballasting sounds. Don't need as many outputs for the plough as a loco.

The v5 is the better choice by far if you want to add even one more function (in my case I definitely want to be able to switch the red marker lights off when not running light engine and that requires another output).

Edited August 18, 2020 by murphaph

[irishthump]

Interesting stuff. Does the extra output you require need to be hardwired to one of the 21 pin connections?

On the subject of the V4 vs V5, nearly all suppliers stopped selling V4's as soon as the V5 was released. ESU were clever enough to not make the V5 more expensive!

If I were you I'd use the V4 in a 141/181. The lighting in those locos is very basic. Unless of course you want to modify the light setup.

[Noel]

32 minutes ago, irishthump said:

Interesting stuff. Does the extra output you require need to be hardwired to one of the 21 pin connections?

On the subject of the V4 vs V5, nearly all suppliers stopped selling V4's as soon as the V5 was released. ESU were clever enough to not make the V5 more expensive!

If I were you I'd use the V4 in a 141/181. The lighting in those locos is very basic. Unless of course you want to modify the light setup.

WheelTappers used V5 for my 121s and recent 141/181s, they sound and drive great. The only thing those early Bachmann/MM 141/181s really lacked for me personally was independent control of the headlamp, and perhaps an easier way of getting inside to install a decoder. The imminent 121s rectify all of that and come with built in speaker.

[murphaph]

So I will install a miniature relay and instead of the common return from the red LEDs going through that switch, it will be connected to either side of the n.o. terminals of the relay. The default state for these lights should be off as locos will generally not be running light engine and thus the red marker lights will be off more often than they are on so it's better to have the default state of the relay as not energised.

The relay coil will be driven by aux 5 with return to the common positive of the decoder.  Very simple job but adds a lot IMO. I will do all the soldering on the loco board rather than touch the decoder. The decoder should still be removable. 

As the proud owner of zero baby GMs I have no idea about the wiring but if I did get one I imagine I would also want the same lighting setup as on a 201 to be honest. If there are no cab lights I would probably add them.

[irishthump]

8 hours ago, murphaph said:

So I will install a miniature relay and instead of the common return from the red LEDs going through that switch, it will be connected to either side of the n.o. terminals of the relay. The default state for these lights should be off as locos will generally not be running light engine and thus the red marker lights will be off more often than they are on so it's better to have the default state of the relay as not energised.

The relay coil will be driven by aux 5 with return to the common positive of the decoder.  Very simple job but adds a lot IMO. I will do all the soldering on the loco board rather than touch the decoder. The decoder should still be removable. 

As the proud owner of zero baby GMs I have no idea about the wiring but if I did get one I imagine I would also want the same lighting setup as on a 201 to be honest. If there are no cab lights I would probably add them.

This type of mod is way above my skill level so I'm very interested to see how that works out. It would be great if you can take a few pictures of the install.

Space is VERY limited inside the baby GMs, so I'm not sure how you would handle the lighting mods.

 

Edited August 18, 2020 by irishthump

[murphaph]

Sure when I get around to the relay for the 201 I will document it. I'm working on a few other things in parallel right now though (trying to resurrect an openDCC controller that I haven't powered up in 10 years and get RocRail to interface to it to run my test oval. The controller is a bare PCB job screwed to the baseboard and took a battering during our house move a few years back).

I will also need to wait until my Loksound v5 actually arrives as it needs that additional output.

[TimO]

This is an interesting project. What sound file are you planning for the v5 and have you any plan to change the speaker?

Have you considered an opto-isolator or is the relay easier to install?

Looking forward to seeing how this progresses and I must open up a 201 to see what ‘s involved.

[murphaph]

A subminiature relay is the easiest and simplest way to do this. You are directly replacing the mechanical switch on the high side of the supply (so a simple open collector transistor circuit will not work). Those little 12v relays cost €1 or so. The relay will rarely need to switch so contact burning is of no concern.

I'll just use the ESU file for the 201 for the time being but I will replace the prime mover sound later with a full throttle one from a US loco with the same engine. There's one in there. I just can't remember the name of it.

I'm going to try an iPhone speaker. I ordered a few.

[DiveController]

That's all very interesting for those of us with a poorer knowledge of this circuitry.

I would do a thread in the DCC section and reference it at the end of this thread for continuity when you get around to it. Thanks for the input.

 

[murphaph]

Sure. I ordered a few relays but somehow managed to order ones too large for this job so they'll go in the spares box and I'll order smaller ones.