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DCC'ing a Walthers HO Turntable

Article Update: 12/13/2012

This article is primarily focused on a Do It Yourself (DIY) conversion of a Walthers HO 130Ft turntable (Part Number: 933-2829) in terms of specifically allowing control the Turntable's bridge rotational speed and direction with DCC Throttle or Cab.

However, I also included information about generally converting any turntable to DCC and additional information about Walthers 90Ft Turntables.

Table of Contents:

1) Turntable Background
2) Basic DCC'ing of a Turntable
3) Walthers 90Ft Turntable
4) Walthers 130Ft Turntable History
5) Walthers 130Ft DCC Control Options
6) Walthers 130Ft "Do It Yourself" DCC Control Option.

1) Turntable Background
If you do not know what a turntable is, go here:

The two key parts of a Turntable are the Turntable's PIT (the hole) and the Bridge that sits in the PIT.  The Bridge carries the track that the locomotive sits on when it is spun around the PIT to the desired track.

Holy Locomotive!  Some one backed up a locomotive into the turntable pit WITHOUT the table lined up for it!

2) Basic DCC'ing of a Turntable 

A scale model turntable has two separate electrical parts.

1) The power that feeds the track located on the bridge.
2) The power to the motor the spins the bridge.  This is often an option.

There is no electrical connection between the track and the motor.  In other words, the two are independently powered and the TYPE of power does NOT have to be the same.  This means you have lots of flexibility.  For complete instructions about basic turntable wiring for DCC, go here:

3) Walthers 90Ft Turntable  

The original and older CornerStone 90FT turntable (Part Number 933-3171)  is a different design than the 130Ft.  This part is currently out of stock at Walthers with no expected date of restock.   

There are TWO Options

CONVERT OLD: There is add on user installed DC motor drive option.  For more information go here: http://www.walthers.com/exec/productinfo/933-1050

Given this has a DC motor, all the options relating to the the conversion of this turntable to DCC is addressed here: http://www.wiringfordcc.com/track_2.htm#a44

BUY NEW: Walthers is still taking reservations for a completely new Cornerstone HO 90Ft turntable with the DCC option already installed.  Expected released is: 4/28/2012  To learn more go here: http://www.walthers.com/exec/productinfo/933-2849

4) Walthers 130Ft Turntable History

Walthers did offer (now discontinued) a CornerStone series 130ft turnable (Part Number: 933-2829) with an integrated motor drive built into the bridge.  Here is the link to the model: http://www.walthers.com/exec/productinfo/933-2829

Unlike the information posted promised, the DCC controlled version was NEVER released.  ONLY the DC version was released.

5) Walthers 130Ft DCC Control Options  

Today that has changed and now there are 3 ways to ALLOW one to get a 130Ft Walthers turntable bridge (Part Number: 933-2829) to be controlled from a DCC throttle or Cab.

1) Upgrade the old version 933-2829 with a new DCC controlled Bridge.
2) Buy the NEW DCC version which comes under a different part number: 933-2850
3) Convert the old version 933-2829 to DCC yourself.  A Do It Yourself (DIY) project.

In detail your options are:
1)130FT UPGRADE: (Shown on the left) Walthers is still apparently taking reservations on a DCC upgrade option for the BRIDGE of an existing 130 Ft turntable. It will include a new control panel and adapter card.  I suspect you will also get a new bridge.  Expected delivery shown is 4/18/2011 which clearly has been passed.  No updated information offered.  I suspect it will become available after option #2 below is released.   To learn more go here: 

2) 130FT PURCHASE NEW:  Walthers is still taking reservations for a complete HO 130Ft turntable with the DCC option installed.  Expected released is: 4/28/2012   To learn more go here: http://www.walthers.com/exec/productinfo/933-2850


Walthers 130Ft "Do It Yourself" DCC Control Option

From day 1 when I purchased the Walther 130Ft turntable when it first came out, I had always wanted to integrate a DCC decoder in to the turntable to control the turntable's movement.  The turntable would have a locomotive address that would allow one to use a DCC Cab or Throttle to control the turntable's bridge rotational speed and direction.   I never got around to doing the conversion myself before I had to sell the turntable for other reasons.  None the less, I did share my ideas "on-line" of how to do it with others who also wanted to do the conversion.  Bert Holmes was one person who listened and did it.   Below is a paper that Bert put together on his experience of doing this project which was also posted on the "DCC4Everyone" group.  At the bottom is what was posted to the group.

Pictures of conversion done by Max is found here:http://home.comcast.net/~maxrob/rr/ttdcc.htm

Note this is an project that requires one with some soldering skill.  If you do this project, you do so at your own risk and Bert, Max nor myself are responsible for any damage.

Control Walthers Built Up Turntables with DCC
by Bert Holmes

I read with interest Mark Gurries suggestion of how he intended to control the Walthers turntable with a DCC module and thought you might be interested in how I have succeeded using a modification of his idea.

In addition to a Lenz set100, I also have the ROCO hand controls with the bidirectional knob, cw forward and ccw reverse, center off, so the motor direction concept intrigued me.  I had a spare TCS T1 module lying around so I wired the red/black to the power input lines.

Note: after reassembly these were attached to the DCC power bus, NOT a separate power supply as Walthers suggests. This could be accomplished by jumpers from the TT track power but see below.

First attempt - didn't work!

I first tried to hook the cw and ccw buttons up with some diodes to the orange and grey wires. Starting the "engine" started the turntable but for reason unknown, when I zeroed the power the leads stayed low so it would not stop - I don't know if it is a characteristic of the T1 or not, but I thought I would try another approach instead. I did not try using a pull up because I had no idea how the "H" bridge was wired internal to the module and I wanted to keep it simple.

Second attempt - success!

To maintain the philosophy of direction control, (in addition to the red/black wires to the power lines as above) I hooked the white/yellow head light outputs to the direction buttons and used the lights on/off function (F0) to start and stop the table in the last selected direction.  It works just fine - only 4 wires and no need to reset the direction until a change is desired.  There was no need to connect the DC negative common since both the control and the module use bridge rectifiers to develop their local voltages and the outputs pull to ground. (and the buttons still work.)   It might have been more complicated if a positive common were required since the controller uses a 12v regulator.  (It's better to be lucky than good.)

One other thing to be aware of. I was very careful to verified that my DCCBus voltage levels were within the turntable specs. If I remember correctly, DCC modules are supposed to be able to handle up to 27v??? or so. Therefore, some systems may be putting out well over 20v. I have my Lenz system set at 16 (and I had checked it with an oscilloscope to verify it when I set it up a while back, so I was comfortable that I met the Walthers spec. There is already precedent in the hobby for this to be a problem. Some sound decoders are only rated for 16v. My son lost two sound modules before he figured out that his system was putting 20.5 volts on the track.

I chose to leave the zero and set functions operated by the local pushbuttons (since the green/purple outputs are not available on the T1) but zero (and I presume set) worked on the light output when I was trying the motor leads so a four function decoder should be fine. (see arrows at buttons in lower left corner for connection points.) Personally I don't see much need for the set button because you need to use the control panel to jog the TT into position before "setting" it, so you might just as well use the set button to finish the job. However, I can see a reason for wiring the "zero" button. The only problem I am having at present is that if another loco shorts out the DCCBus while the TT is rotating it looses its current position memory and needs to be zeroed. I am going to solve this by putting it on a separate (DCC booster) Bus I reserve for accessory decoders only. It also allows me to keep switch machines alive in case of a track short.

What I want to do now is figure out how to use JMRI to program a time delay appropriate to the distance and direction between current and desired alignment positions to operate the functions and direction from a panel. Routes only seem to be able to control stationary decoders and I have not found a programmable time delay there either. I suspect I will have to get involved with scripts but it seems a bit much to handle for a first project.

PS 12/31/07:  I have subsequently substituted a decoder with the extra function output and attached it to the zero button on the TT controller. It too is working just fine. I programmed it to work as F3 just to make it less likely that I would press it accidentally when going for the lights (F0). I used a Lenz 1035 but that is overkill for sure. I just happened to have a spare lying around.

Note: (Neither Bert nor Max accept responsibility for any damages; use this project at your own risk.) 

Bert Holmes
Chief Gandy Dancer on the HWH-RR-RR
(Hardly worth having-recycled and reconditioned-railroad)