Class 50 Roof Fan Micro Motor Voltage and Amp rating

[DCC_Dublo]

Hello,

I have a Hornby Class 50 (R2802XS) and want to scrap the traditional rubber band/flywheel driven mechanism of the Roof Fan for a micro motor. I am going to replace the LokSound V3.5 DCC Decoder for a LokSound V5 (ESU 58419 or 58412, depending on how difficult it would be to convert it to PluX22) and also replace the speaker (due to the different impedance rating needed, 8Ω - 32Ω, rather than 100Ω).

The reason I want to convert the loco to PluX22 is because the socket has powered outputs from Aux3 to Aux7 whilst a 21MTC has these as logic level outputs only (cannot supply power, only a signal). And if I wanted to add cab lights to Aux 1 and 2, I have no more powered outputs on the plug. Instead I would have to solder another wire to one of the pads on the decoder (not very plug-and-play), or rectify power from the wheel pickups to power the motor, which requires more electronics (and money).

On the Manual on ESU’s website it states that each powered output can handle up to 250mA of current, and I run the Hornby Elite controller (with a booster on an isolated piece of track) and they should run at 15V.

I have 2 questions:

1. Am I correct to say that the micro motor (if I want to power it through the decoder) has to draw less than 250mA and be rated for 16V or more?
2. Can I just remove the PCB in the locomotive (1621-X021) and replace it for a PluX22 adapter (e.g. ESU 51958 PluX22 adapter board 1) and attach the lights, cab lights, micro motor and speaker to that? Or would I have to add my own resistors or other electrical components in? If so, does anyone have a wiring schematic for this board? I was not able to find one.

Answers to these questions would be highly appreciated,

DCC_Dublo.

Picture of the existing 21MTC PCB

ESU’s Manual stating a maximum of 250mA of power per output.

PluX22 connector has power from Aux1 to Aux7 on the pin.

[96RAF]

1. Yes and no. The motor needs to draw less than the function output limit. Generally these motors draw much less than that. Function outputs are usually 12v DC not the 15v pseudo AC the Elite puts on the track.
2. Yes, matching the connections to those of the Plux layout. Pull the NEM standard for it. There is no wiring diagram for the loco PCB in the public domain so you will have to reverse engineer by trace if you need to, but all necessary resistors and associated components are either on the main PCB or on lighting daughter boards. As the model is the old XS factory sound fit, the speaker wires should already be there.

Be aware that the old Hornby sound locos may have common anode (CA) or common cathode (CC) lighting, so you need to trace back the led commons.

The old Bromsgrove Models DCC installations page used to have wiring guides for complex lighting conversions including which were CA or CC circuits. The site has been hard to find on google recently, although they still contribute on RM Web forum.

Some 21-pin decoders can have their functions toggled from logic to full potential.

[ColinB]

I think you need to read the specification on the LokSound decoder, the logic outputs for Aux 3 and 4 will be a function of the decoder. If they are only logical outputs there is a guy on EBay (blwtechnicalservices) that did make an interface circuit, so seeing as you are adding the fan you could add that next to it. It has got to be simpler than fitting a Plux22.

[LMSFan72]

I traced boards on the Class 50s a while ago, see the attached topic, although the images now appear to be missing:

https://uk.hornby.com/community/forum/class-50-circuit-board-traced-diagram-attached-but-how-does-it-work#post-251714

Here's one of the 8-pin versions:

Note that the light boards on the 8-pin board are common negative so the re-wiring is not just confined to the main board - I tend to desolder the LEDs and turn then around and re-use the boards with additional wires added.

I don't think I ever traced a 21-pin....

[Flashbang]

Assuming the existing ESU LokSound V3.5 decoder is working correctly; I personally wouldn't mess around trying to upgrade the decoder fittings to another type! Instead, I would add a second low cost wired decoder and use its motor output (Orange and Grey wires) to drive the fan motor so as the fan motors speed can be easily adjusted and then use its 4 (or more?) Function outputs to operate other devices - LEDs etc grinning

[ColinB]

Seeing as the sound decoder uses the back emf to control it adding a second decoder is not going to work too well. LokSound V3.5 is an obsolete type and even worse it uses a 100 ohm speaker which is not a good idea. Sadly with most sound decoder you can get them upgraded for £30, but this service is not available for version 3.5. I cannot understand anyone that hardwires a DCC decoder you are just asking for trouble.

[Flashbang]

TBH Ive never read such utter rubbish! - Sorry, but if you believe adding a second decoder to a fully working one is a issue, you need to understand DCC far more. Bemf has nothing whatsoever to do with the second decoders operation - This second decoder only providing motor (fan) and Function controls!

Adding a second decoder is very simple and needs nothing more than room for the decoder and a soldering iron!

It introduces a second motor output (used for the fan motor) and many function controls!

Edit to correct a typo spelling errror!

[ColinB]

Having spent entirely my career working on microprocessors and digital communications, I understand DCC perfectly. If you use another decoder you won't be able to vary the speed of the fan motor independently because the fan speed would be dependent on the loco speed, unless that is what you want. If you want to add another decoder then do it, personally I would just buy the interface board off EBay it is only £4.00 and then control the fan on/off with a function key. I suppose the only issue is the inductive load but then again you would just need a reverse biased diode across the terminals.

It is a really interesting idea, what micromotor are you thinking of using, I wouldn't mind doing that with my ones. I do have a preorder for one of the new Bachmann diesels with the same arrangement so it will be interesting to see how they do it.

[Fishmanoz]

If you are going to have versatility on functions and motor control with the second decoder, you are going to need it on a second address. I think that solves all the limitations you’ve mentioned Colin? Without the 2nd address, the functions on decoder 2 are only double-ups of decoder 1, along with motor speed.

[DCC_Dublo]

Hello everyone,

To answer ColinB’s question: I honestly have no idea what kind of micro motor I was wanting to use. Something that fits, is powerful enough to spin the fan and doesn’t draw too much power, as well as not spinning at something ridiculous like 50,000 rpm. That’s quite literally the criteria I have. I had a look on eBay for the adapter boards you recommended by blwtechnicalservices and he was a seller with no products. I don’t think they sell them to customers in Australia :(

Flashbang and ColinB: The main reason I wanted to upgrade my ESU LokSound V3.5 actually has nothing to do with the micro motor. I would have just kept that decoder if that was the reason. It is actually because I would like to add a sound file (I believe made by Jamie Goodman) for a Class 50 which walks all over Hornby’s sound file (when paired to a good speaker). Hence the reason for the upgrade to either the 21MTC or PluX22 variants of the LokSound V5.

I also would prefer not to add a second decoder to the locomotive just for the sake of simplicity. And when it comes to DCC addresses, I would like to use one. As Fishmanoz pointed out the only way I might get it to work is with 2 addresses. Not what I’m personally looking for. But a good idea none the less, (at least seems so to me, someone who has very little experience with DCC).

It should be noted I was under the impression that the real life Class 50’s roof fan turned on and off when needed (not in sync with the motor) and all I wanted was an on/off function. I don’t really care about varying speed of the fan. Or an I mistaken and was it crankshaft driven or something else similar in real life?

LMSFan72 thank you for the drawings. I know they aren’t of this circuit board but honestly anything that might help me with this PCB which seems to have no online drawings are useful.

I think what I might have to do from here is ask a friend of mine (who is good at electronics) to trace the board for me (as I wouldn’t have a clue where to start) and I’ll get back to this discussion with those findings. Maybe it will help someone else trying to figure out something else with this particular PCB? Might do the lighting boards at each end of the loco whilst I’m at it (unless they already exist online… I haven’t looked yet).

Edit: I almost forgot. Thankyou to 96RAF for clearing up those questions about the voltage and amperage.

[ellocoloco]

@Lewis. I can't really help with the specifications for your project but remember seeing something similar a while ago.

This is a link to Spanish Railway Forum, Forotrenes, where one the modellers installed Fans on a RENFE 4000 using micro motors very similar to what you are proposing. The model doesn't have sound and he says he would have to reposition the speaker if it were to. I use google translate for this type of post and somethings may be missed but judging by the content and detail of this thread, you will have no problem understanding what he's up to.

Hope it helps and looking forward to seeing a picture of your completed 50!

[96RAF]

Extract from a Class 50 train sim ops manual which tells of the fan being multi-speed and switched by thermostat so very likely to be electrically driven.

[96RAF]

Also a selection of micro-motors pulled from a tiny RC car that I intended to use to power a Road-Rail Landie, based on the picture of the chassis shown.

Edit - the new HSTs are advertised as having a motor driven fan - worth waiting for the associated service sheet and trying to find them as spares.