Powerful CDU

Post all your model railway electronic problems, solutions and discoverys here.
User avatar
D605Eagle
Posts: 2598
Joined: Mon Mar 22, 2010 12:58 am
Location: Staffordshire
Contact:

Powerful CDU

Postby D605Eagle » Mon Jul 09, 2018 2:36 am

I've created a bit of a behemoth of a diode matrix for my rather complex station section of my layout. Because of this some of the route selections will make up to 8 point motors fire at once. I'm using peco point solenoid motors and was going to build a CDU with a large amount of capacitance so it will be capable of working so many point motors at once. When only one or two points are thrown at once will having all that grunt in the CDU damage the points due to throwing them too hard?

User avatar
RAFHAAA96
Posts: 501
Joined: Tue Feb 19, 2008 1:39 pm
Location: Cyprus

Re: Powerful CDU

Postby RAFHAAA96 » Mon Jul 09, 2018 7:14 am

I wouldn’t think so as with a normal CDU and a single point you need to flip a point a few times after power down to deplete the caps, so I guess the solenoid only takes a small gulp of the available power within the milliseconds available at switch throw.

I could be talking complete and utter drivel of course and someone will be along soon to tell me that.

Edit:
I use a GM standard CDU powered from an old HM2000 DC controller and I can continually and reliably manually switch pairs of Hornby surface mount solenoids. These little black point motors are more current hungry than the regular underfloor version but not as hungry as Seep motors.

My old layout used the same CDU with Hornby underfloor solenoids and Rocrail could set a route of up to eight points which all fired OK in timed sequence.

Rob
Last edited by RAFHAAA96 on Mon Jul 09, 2018 12:51 pm, edited 1 time in total.
RAF Halton Brat - 96th Entry
http://www.halton96th.co.uk

User avatar
luckymucklebackit
Posts: 3078
Joined: Mon Jul 18, 2011 7:05 am
Location: Eaglesham, south of Glasgow
Contact:

Re: Powerful CDU

Postby luckymucklebackit » Mon Jul 09, 2018 8:33 am

I have a similar set-up with multiple Peco point motors being fired at once, I have a Gaugemaster CDU with an additional capacitor (can't remember the value - will check tonight) soldered in parallel and fed by an 18V AC power source. Never had any issues with it failing to set the route,

Jim
This Signature Left Intentionally Blank, but since I have written this and I intended to do it, this Signature is intentionally not blank. Paradox or What?
My layout - Gateside and Northbridge
Image

User avatar
Bufferstop
Posts: 10851
Joined: Thu Mar 11, 2010 12:06 pm
Location: Bottom end of N. Warks line

Re: Powerful CDU

Postby Bufferstop » Mon Jul 09, 2018 10:14 am

The danger isn't failure to throw it's blades broken from tie bar. Make sure any singly operated points have their springs in place. If the operation is still too vicious add some friction to the tie bar. If the point motor isn't under the point make the linkage a bit springy to absorb the shock.
Growing old, can't avoid it. Growing up, forget it!
My Layout, My Workbench Blog and My Opinions

User avatar
D605Eagle
Posts: 2598
Joined: Mon Mar 22, 2010 12:58 am
Location: Staffordshire
Contact:

Re: Powerful CDU

Postby D605Eagle » Mon Jul 09, 2018 5:06 pm

luckymucklebackit wrote:I have a similar set-up with multiple Peco point motors being fired at once, I have a Gaugemaster CDU with an additional capacitor (can't remember the value - will check tonight) soldered in parallel and fed by an 18V AC power source. Never had any issues with it failing to set the route,

Jim

Failure to set the route isn't what I'm worried about, its if a single point is thrown, it getting wacked over too hard and damaging it due to the large amount of power stored in the CDU. However I think Rob may be right because in another section of the layout with a CDU, operating a single point can be done several times after the power is removed. I guess it will be suck it and see!

User avatar
D605Eagle
Posts: 2598
Joined: Mon Mar 22, 2010 12:58 am
Location: Staffordshire
Contact:

Re: Powerful CDU

Postby D605Eagle » Mon Jul 09, 2018 5:07 pm

Bufferstop wrote:The danger isn't failure to throw it's blades broken from tie bar. Make sure any singly operated points have their springs in place. If the operation is still too vicious add some friction to the tie bar. If the point motor isn't under the point make the linkage a bit springy to absorb the shock.

They are all directly under the points screwed to the underside of the board.

User avatar
Bufferstop
Posts: 10851
Joined: Thu Mar 11, 2010 12:06 pm
Location: Bottom end of N. Warks line

Re: Powerful CDU

Postby Bufferstop » Mon Jul 09, 2018 5:29 pm

If you find any going over too hard try a thin sliver of plastic under the ends of the tiebar. You could always experiment with shunt resistors across the coils of those points.
Growing old, can't avoid it. Growing up, forget it!
My Layout, My Workbench Blog and My Opinions

Suzie
Posts: 268
Joined: Tue Dec 17, 2013 11:46 pm

Re: Powerful CDU

Postby Suzie » Mon Jul 09, 2018 5:37 pm

Firing from a CDU is not going to break the tie bar on a Peco point unless the voltage and therefore the initial current is excessive.

Around 4700uF at around 30V should be enough to shift eight PL10s if the wiring is good, and that should not be excessive for two.

If you have to increase the voltage to make it work you might need better wiring.

User avatar
D605Eagle
Posts: 2598
Joined: Mon Mar 22, 2010 12:58 am
Location: Staffordshire
Contact:

Re: Powerful CDU

Postby D605Eagle » Mon Jul 09, 2018 5:49 pm

IIRC the voltage was 28 volts when I checked it with the last CDU I built. That has 9400uF on board. I was thinking of putting 18800uF on the new one, but I guess thats just too excessive! I'm using fairly substantial wiring.

User avatar
Peterm
Posts: 1428
Joined: Fri Nov 09, 2007 1:26 pm
Location: Bribie Island. Australia

Re: Powerful CDU

Postby Peterm » Tue Jul 10, 2018 3:02 am

When I was using Peco solenoids, I built my own cdu for a matrix. Four x 4,700 mf caps shifted eight perfectly well, but for single points, I used a 5 watt resistor on each one, but can't remember the value. It did the trick though.
Pete.

User avatar
D605Eagle
Posts: 2598
Joined: Mon Mar 22, 2010 12:58 am
Location: Staffordshire
Contact:

Re: Powerful CDU

Postby D605Eagle » Tue Jul 10, 2018 3:05 am

Thanks Pete. I would have thought a 1 watt would suffice as its only momentary power. There are a couple of points that only ever work singularly or in pairs.

User avatar
Bufferstop
Posts: 10851
Joined: Thu Mar 11, 2010 12:06 pm
Location: Bottom end of N. Warks line

Re: Powerful CDU

Postby Bufferstop » Tue Jul 10, 2018 10:31 am

One Watt is probably OK but unless there is a large price difference why skimp. You'll find that different manufacturers have their own interpretation of what constitutes adequate for 1W. You'll find that quality of production varies from just meets spec to so over-engineered there's no need to check.
Growing old, can't avoid it. Growing up, forget it!
My Layout, My Workbench Blog and My Opinions


Return to “Electronics”

Who is online

Users browsing this forum: No registered users and 2 guests