Using a cdu

[KieFowler27]

I plan too build a dcc layout with around 30 seep pm1 point motors, and 30 electrofrog code 75 points using 16 curved for the fiddle and 14 for the medium straights for the scenic section, how many cdus would this require and what type is best, have read that it doesn’t matter how many points on the layout there are and that you can use only one cdu however, the gaugemaster and other cdu sites state a max of 6 points can be used per cdu, does this mean that the 6 points are moved at the same time and that id only need one fairly powerful cdu for all 30 as it’s likely I’ll occasionally only  move around 5 or 6 pints (fiddle yard changes and scenic switches) and in short time (2/3 seconds) between each switch or that I’d need 6 cdus too run 5 points Each for the whole layout ? 

Thanks for any assistance 

[kevinlms]

1 hour ago, KieFowler27 said:

I plan too build a dcc layout with around 30 seep pm1 point motors, and 30 electrofrog code 75 points using 16 curved for the fiddle and 14 for the medium straights for the scenic section, how many cdus would this require and what type is best, have read that it doesn’t matter how many points on the layout there are and that you can use only one cdu however, the gaugemaster and other cdu sites state a max of 6 points can be used per cdu, does this mean that the 6 points are moved at the same time and that id only need one fairly powerful cdu for all 30 as it’s likely I’ll occasionally only  move around 5 or 6 pints (fiddle yard changes and scenic switches) and in short time (2/3 seconds) between each switch or that I’d need 6 cdus too run 5 points Each for the whole layout ? 

Thanks for any assistance 

The ratings of a CDU generally refer to how many point motors, it can throw AT ONCE.

 

But how many you NEED to throw at once is the question you need to ask. That usually means from where your loco currently is, to where you want it to get to in the one move.

So you will never need to throw 30 at once, usually between 1 and 6.

 

So the answer to how many CDU's you need is probably one, although 2 may be more convenient on a large layout, with more than one operator. Basically, it's so there is no problem, if both decide to throw points at exactly the same time.

 

But I do think you need to do quite a bit more research on point control.

[jonhall]

As KevinLMS has said, a conventional CDU should be fine in most normal applications, where you are firing up to about 6 motors at once, and have reasonable wiring supporting it.

 

There are a few tricks along the way that help - my club managed to achieve a perfect storm

 

we used computer ribbon cable which was too small cross section for the current, and compounded it by making quite long wiring runs terminated at each baseboard with veroboard distribution.

 

We had an entry to the fiddle year that could have required us to simultaneously fire two motors on a double switch, two on a 3 way and potentially 3 more single points - at EACH END of a through fiddle yard.

 

Because route setting was a nightmare, we used a diode matrix, and there was some loss at each diode.

 

To try and fix the above they started using bigger and bigger capacitors, which didn't fix the problem, but ended up having slower and slower recharge times!

 

There was a system that offered smaller CDU's that were intended to just fire one or two points at a time, but distributed at the 'point end' of the circuit, not the control panel end - instead of sending the burst of current all the way down the layout, you sent the 'trigger' signal instead - I guess it was intended for remote loops on very large layouts. I don't recall who made it.

 

Jon