How to connect a Heljan roof fan to a zimo MS950

[RvSwol]

Hello , Is there anyone who can help me further along the way. 
I have the sound decoder file ZS33ASL class 33 from Digitrains  L.t.d,  and loaded it into the Zimo MS950.

 

My question is about the Heljan roof fan of the class 33. 

The Heljan roof fan is not polarity sensitive, so it does not matter how it is connected.  
The original Heljan PCB was taken out and in its place was the Zimo PCB LokPL 950 that comes along with the Zimo MS950. 

From the supplied documentation from Digitrains,  no wire connections are listed .

I implemented the assigned function assignments from Soundfile of Digitrains ZS33ASL class 33 and wiring to the the Zimo PCB. 
Everything on the Heljan Class 33 runs and functions as named in the appendix of the soundfile. 

 

Was left how to connect the roof fan. 
The roof fan runs best on 1.5 volts. ( tested with a battery ).

I want to control the running of the roof fan , to the designated sound function of the F key 15 , ( Sound Fan )  with the free function output FA5 .  

Considering the sound of the Fan is also recorded as random sound. 

 

Given that the Comm + gives the full track voltage ( 17 volts ).

That is too high to bridge with resistors to 1.5 volt  , besides it can give unwanted heat development. 

So I want to switch out to the +5 volt comm.  So the Red wire has been soldered  to +5 volt comm

The other black wire of the Heljan roof fan has been soldered  Function output FA 5. 

FA5 is technically an OpenCollector output of a transistors ... so when active (FA5 is "on") it draws to ground (so voltage difference between the consumer poles exists. 

 

Now I want to get from the 5 volts to a voltage of 1.5 volts by adjusting CV 60 value .

However, it has  been made clear to me,  that voltage adjustment  this is not done with CV 60 

 

CV#60 defines a PMW-value ... so simple an "on-to-off-rate" for FO(s) 

 

 If you set CV#60=128 (which is about the half of 255, half of the time the FO is "on" (draws to ground/0V) and half of the time the FO is "off" (high impedance) ... so in the case of an LED light , is then shining for 1 Millisecond, then 1 Millisecond it is off, then 1 Millisecond it is on, and so on. ... but the slow human eye don´t notice that very fast on/off rate (so you didn´t see the single turn on or the single turn off) ... you only notice that a LED is not shining so bright (in whole), when it is about 50% of the time off.
When  CV#60=204 it means that 80% of the time the LED is "on" ... and 20% of the time the LED is "off".

With a CV60 value you NEVER change any voltage.

So given the delta percent value between 5 volts and 1.5 volts the number -minus 70,  would be the Dim factor which also applies to the Fan Motor .

So that means the value for CV 60 = 179 ( 255 x 0.7=178.5 ). 

 

However the value of CV 60 gives 70 % reduction to all FA outputs due to the PWM. 

To excludes specific functions from dimming, i assigned the value 191 to CV#114, so that the dimming value  would apply only to the FA5 output.

The front and rear lights as well as FA1, FA2, FA3, FA4 , FA6 would then not be dimmed. 

 

However, despite all the preliminary work, it does not work.

 If I switch F15 on or off no reaction of the Fan .

What am I overlooking. 
Should I not use the 5 volts and should I still use the Common Plus that has the track voltage of 17 volts. 

Happy to hear your views or simpler solution 

 

Kind Regards 

Rupert 

 

Excuse my poor command of the English language