DCC Roof Fans on Heljan Western

Discussion in 'Techniques' started by Tim Giles, 19 April 2020.

  1. Tim Giles

    Tim Giles Member

    Has anyone successfully managed to get the roof fans working using the Legomanbiffo Class 52 decoder.
    I have got all the other functions working Ok but getting the fans to spin is something that is proving a problem.
    Ideally I want them to work on F12 and related to loco speed similar to the DC version.

  2. richard carr

    richard carr Western Thunderer

    Hi Tim

    Getting the roof fans to work on Heljan locos can be a pain.

    The first question is, do the fans have a separate small pcb in the roof contolling them, or are they controllered from the main Heljan PCB ?

    This is the separate roof mounted PCB in a class 50 Heljan would have used the same one in the Western.

    If it doesn't have one of these the same components will be on the main pcb.

    It is very difficult to get the fans to run at a correct speed without these. DCC uses a constant 12-14 volts which makes the fan run really fast and noisy when the should be quite slow, the blue and white potentiometer on the board can reduce the voltage so that it runs at more realistic speed.

    You won't be able to get the fan to run as it does on DC, as DC is a variable voltage system, ie as you turn the controller up it increases the voltage to make the loco run faster and does the same to the fan.

    As for getting it to run on F12 I assume it's an ESU decoder and you would be best of asking Leggoman how to do it, I would use a Lok Programmer but if you haven't got one and know how to use it asking him for the CV settings to do that is by far the easiest way.

    KeithRE and Dog Star like this.
  3. TheSnapper

    TheSnapper Western Thunderer

    Hi Tim

    Have you contacted Bif? He is a nice bloke & very helpful.

    I agree with Richard, and almost think it's not worth the effort.
    I have often thought about attempting to devise a method to drive them by air movement, like a windmill.

    I did a Heljan Western here and it has a seperate fan PCB (and two sets of fans!)

    I haven't tried it, but I wonder if it would work related to loco speed, just by connecting the fan feed to the motor output on the decoder, rather than to the AUX output controlled by F12.
    You could trim the speed with the on-board potentiometer on the fan PCB, but the fan would be ALWAYS-ON , except when the loco is stationary.

    Not sue if it might confuse the decoder back-emf. I may try it later....

    (Another) Tim
  4. KeithRE

    KeithRE New Member

    Hi Tim(s),
    Just a few thoughts - I'm not familar with the particulars in this case. Could you control a small relay from one of the outputs? If so, you could use it to control the feed to the fan the motor output - a smallish value resistor ('select on test') might be useful to 'isolate' and back-emf effects but I'd expect they would be quite small compared with the two heafty Heljan motors.
    Best of luck, interested to know how you get on.
  5. Tim Giles

    Tim Giles Member

    Thank you all for your replies and varied interesting suggestions/solutions.
    I have got quite a lot of things that I could now try.
    If I succeed in achieving the effect I am looking for I'll post my solution.

  6. class27

    class27 Member

    Having just done this you will need to speak to Legoman as it requires some alteration needing a lokprogrammer. You can adjust the voltage on Aux 1 once it is configured to work with F12 and there is a light mod that he can do that gives more prototypical operation of the lights.
    I now have all the fans working on both Loksound (thanks to Legoman) and my zimo Locos thanks to Paul Chetter if you play around with the voltage CV you can get very quiet operation of the fans using the small board pot for final adjustment. I have even managed to retrofit a small board to my MK1 Hymek and even it runs quiet
    The fan thing has been overlooked on Heljan diesels as Gimmicky and noisy, but with some adjustment they can all work well
    KeithRE likes this.
  7. TheSnapper

    TheSnapper Western Thunderer

    Hi Tim

    Just to follow up on my suggestion:
    Wiring the fan directly to the motor outputs on the decoder does actually work, and fan speed increases with loco speed.
    Obviously the fan stops when the loco come to a halt.
    However, is this prototypical?

    The fan speed will need careful adjustment using the potentiometer on the fan control board.
    I found it difficult to get the the fan to start until the loco is travelling at some speed.


  8. richard carr

    richard carr Western Thunderer

    Tim and Tim

    No it is not prototypical for the fan to stop when the loco stops. The fans are as I understand temperature controlled although having said that I don't ever recall seeing a loco with the engine running where the fan was not moving.

    I also believe that the fan speed is fairly constant and does not increase with loco speed.

    The problem with most decoders is that the function outputs are at full voltage ie 12, which makes the fan rotate far too fast and often makes it very noisy too.

    You need to use the potentiometer that is either on the main Heljan PCB or sometimes comes as a separate PCB to lower the voltage to get a realistic spin speed.

  9. Ressaldar

    Ressaldar Western Thunderer

    Hi Tim, Tim and Richard,

    back in October 2018 I installed an ESU V4XL into a Heljan 47 for a fellow Club member and discussed the fan speed problem with SWDigital who had supplied the decoder. Their response was that on some Heljan diesels there is a 'pot' which can adjust the speed or if the 'pot' is not present, set

    CV31 = 16

    CV32 = 0

    CV294 = 0 - 31 (output speed)

    I adjusted the CVs and yes it does control the speed, but as stated elsewhere here, a certain amount of sound is still heard.

    I hope this is of interest.

    Stay safe all.


  10. richard carr

    richard carr Western Thunderer

    Hi Mike

    Thats one I'll try to remember, you can do a similar thing on Zimo decoders but the voltage is controlled by pulse modulation so when you get the voltage down it does turn the fan but not on a consistent basis, sometimes it will work, sometimes it won't start at all and the fan needs a nudge to get it going.

    The Heljan PCB is by far the best solution and you can buy the separate one as a spare part from Gaugemaster who are now doing the Heljan spares.

  11. class27

    class27 Member

    The pulse modulation thing is interesting and may explain why a combination of meddling with CV and the Pot gives the quietest operation
    My Hymek had a really noisy fan on DC so I disconnected it for DCC until recently. I then tried it with a spare board from a class 26 and some CV info from Paul Chetter and it cannot be heard over the engine sounds.
    On all of my locos with a cooler group sound, the fan noise cannot be heard over the cooler group sound.
    None of the voltage CV's or pots are set the same, each loco seems to be different, but i think it is worth the effort
  12. class27

    class27 Member

    Apologies to the OP for a small Hi-jack. Does anyone out there have any Fan motors and worm shafts they do not need I need to reinstate 2. Pm if you can help
  13. Tim Giles

    Tim Giles Member

    Apology accepted.
  14. Tim Giles

    Tim Giles Member

    Reviewing the suggestions posted so far it would seem that a solution which emulates the prototype would obviously be the best.
    If the fans are temperature controlled in the real thing then they would respond when the engines are working hard so perhaps a possible solution is to incorporate a circuit into the output to the motors which converts the current into a voltage control to the fan motors which is user adjustable. Thus when the loco is idling the fans are off, when running light then the fans just gently spin and when the loco is pulling a 10 coach train then the fans run quickly.
    Looks like a challenge for the electronics experts amongst us or even the MERG members.

  15. class27

    class27 Member

    On Paul Chetters Class 25 sound project. The cooler group sounds cut in and out (just like an ordinary car would when hot) and this also switches the fan on and off without having to use the relevant F key, which is quite cool.
    The big problem is the differing types of drive used in the prototypes, from mechanical, which would be speed proportional, to hydraulic and electric motor, which I guess would be single speed (flat out)