Auto-reversing for continuous operation of a point-to-point layout

Auto-reversing for continuous operation of a point-to-point layout

Post by Digital Railroade » Fri, 20 Jun 2003 02:29:14



We know of one device that automatically senses end-of-track and reverses
the locomotive's direction, but we believe that it's for DC layouts only. Is
there a similar device for DCC layouts?

The Conductor
Digital Railroader LLC

 
 
 

Auto-reversing for continuous operation of a point-to-point layout

Post by Bil » Fri, 20 Jun 2003 13:04:54


We know of one device that automatically senses end-of-track and
reverses the locomotive's direction, but we believe that it's for DC
layouts only. Is there a similar device for DCC layouts?
--------------------------------------------------
Maybe the MRC #AD520 Auto Reverse Loop Module could be adapted to do
what you want. The additional switches and/or electronics could be
placed on/in the trackwork

Bill
Bill's Railroad Empire
N Scale Model Railroad:
http://www.billsrailroad.net
Brief History of N Scale:
http://www.billsrailroad.net/history/n-scale
Resources: Links to over 500 helpful sites:
http://www.billsrailroad.net/bills-favorite-links
Bookstore: http://www.billsrailroad.net/bookstore.html

 
 
 

Auto-reversing for continuous operation of a point-to-point layout

Post by Gregory Procte » Fri, 20 Jun 2003 13:27:04


Quote:


> We know of one device that automatically senses end-of-track and
> reverses the locomotive's direction, but we believe that it's for DC
> layouts only. Is there a similar device for DCC layouts?
> --------------------------------------------------
> Maybe the MRC #AD520 Auto Reverse Loop Module could be adapted to do
> what you want. The additional switches and/or electronics could be
> placed on/in the trackwork

That item is designed to reverse the track polarity so that a train can
negotiate a reversing loop without DPDT switches. DCC decoders don't see
polarity, but track joins do.

Regards,
Greg.P.

 
 
 

Auto-reversing for continuous operation of a point-to-point layout

Post by Bil » Fri, 20 Jun 2003 13:57:10


Greg.P. replied:
That item is designed to reverse the track polarity so that a train can
negotiate a reversing loop without DPDT switches. DCC decoders don't see
polarity, but track joins do.
--------------------------------------------------

Greg, thanks for pointing this out. My aging brain realized that just
after I posted the reply.

Bill
Bill's Railroad Empire
N Scale Model Railroad:
http://www.billsrailroad.net
Brief History of N Scale:
http://www.billsrailroad.net/history/n-scale
Resources: Links to over 500 helpful sites:
http://www.billsrailroad.net/bills-favorite-links
Bookstore: http://www.billsrailroad.net/bookstore.html

 
 
 

Auto-reversing for continuous operation of a point-to-point layout

Post by Robert Helle » Fri, 20 Jun 2003 19:39:39



  In a message on Thu, 19 Jun 2003 00:57:10 -0400 (EDT), wrote :

B> Greg.P. replied:
B> That item is designed to reverse the track polarity so that a train can
B> negotiate a reversing loop without DPDT switches. DCC decoders don't see
B> polarity, but track joins do.
B> --------------------------------------------------
B>
B> Greg, thanks for pointing this out. My aging brain realized that just
B> after I posted the reply.

One *downside* of DCC is that it is not really good for 'dumb'
automation (dumb == fun with simple logic circuits driving relays).
For a simple store-display type layout, unattented operation, DC is
still useful.

It is possible to do this with DCC, but would require a *lot* more
electronics, since you need to form the DCC packets that implement the
reversing commands for the locomotive.  It might be easier for more
Model RRs to just buy themselves a 'cheap' PC and write a VB (or Bash
Script, depending on O/S) script.

Beware of the axiom: "If all you have is a hammer, everything looks like
a nail."  Sometimes you just need to use a screwdriver...  DCC is no
more a universal tool than a hammer is a universal tool.  Sometimes you
just need to use DC...

B>
B> Bill
B> Bill's Railroad Empire
B> N Scale Model Railroad:
B> http://www.billsrailroad.net
B> Brief History of N Scale:
B> http://www.billsrailroad.net/history/n-scale
B> Resources: Links to over 500 helpful sites:
B> http://www.billsrailroad.net/bills-favorite-links
B> Bookstore: http://www.billsrailroad.net/bookstore.html
B>
B>                                                                                                                  

 
 
 

Auto-reversing for continuous operation of a point-to-point layout

Post by Mike Tennen » Fri, 20 Jun 2003 21:43:49


Quote:

>We know of one device that automatically senses end-of-track and reverses
>the locomotive's direction, but we believe that it's for DC layouts only. Is
>there a similar device for DCC layouts?

I don't think so. I make one for DC and have pursued the same question
unsuccessfully because I'd like to offer one to my customers. (I hope
I'm wrong and someone will point one out.)

The primary problem is that the technology is totally different.  With
DC,  you simply switch polarity of the track and the engine switches
direction. All you have to do is sense that the engine is in position
to change direction.

Switching track polarity on DCC doesn't effect the direction of the
engine.  The Command Station has to tell it to stop and switch
directions, which is a whole different ballgame.

It can be done with a computer, position sensing, and the appropriate
software. Theoretically it could be done with a microchip of some sort
for  a stand-alone system, but the variables involved would be
daunting.

Mike Tennent
"IronPenguin"
Operating Traffic Lights
Crossbucks
Special Effects Lighting
http://www.ironpeng.com/ipe

 
 
 

Auto-reversing for continuous operation of a point-to-point layout

Post by Steve Wats » Sat, 21 Jun 2003 01:58:24


Quote:


>   In a message on Thu, 19 Jun 2003 00:57:10 -0400 (EDT), wrote :

> B> Greg.P. replied:
> B> That item is designed to reverse the track polarity so that a train can
> B> negotiate a reversing loop without DPDT switches. DCC decoders don't see
> B> polarity, but track joins do.
> B> --------------------------------------------------
> B>
> B> Greg, thanks for pointing this out. My aging brain realized that just
> B> after I posted the reply.

> One *downside* of DCC is that it is not really good for 'dumb'
> automation (dumb == fun with simple logic circuits driving relays).
> For a simple store-display type layout, unattented operation, DC is
> still useful.

> It is possible to do this with DCC, but would require a *lot* more
> electronics, since you need to form the DCC packets that implement the
> reversing commands for the locomotive.  It might be easier for more
> Model RRs to just buy themselves a 'cheap' PC and write a VB (or Bash
> Script, depending on O/S) script.

??
Unless I badly misunderstand the way DCC works, sending reversing
commands to the loco isn't the right thing to do.  "Forward" and
"backward" are determined strictly by which way the decoder is wired.
I gather there's a few ways of handling loops under DCC, but they all
basically work by detecting the polarity mismatch, and reversing the
track feed -- not too different in principle to how it's done in DC.

One obvious way, for the simple case of an end loop, is to feed loop
power through the loop turnout.  When the train is completely in the
loop, throw the turnout.  Loop polarity now matches the main at the
exit point.

-- Steve

 
 
 

Auto-reversing for continuous operation of a point-to-point layout

Post by Paul Newhou » Sat, 21 Jun 2003 02:11:28




Quote:


>>   In a message on Thu, 19 Jun 2003 00:57:10 -0400 (EDT), wrote :

>> B> Greg.P. replied:
>> B> That item is designed to reverse the track polarity so that a train can
>> B> negotiate a reversing loop without DPDT switches. DCC decoders don't see
>> B> polarity, but track joins do.
>> B> --------------------------------------------------
>> B>
>> B> Greg, thanks for pointing this out. My aging brain realized that just
>> B> after I posted the reply.

>> One *downside* of DCC is that it is not really good for 'dumb'
>> automation (dumb == fun with simple logic circuits driving relays).
>> For a simple store-display type layout, unattented operation, DC is
>> still useful.

>> It is possible to do this with DCC, but would require a *lot* more
>> electronics, since you need to form the DCC packets that implement the
>> reversing commands for the locomotive.  It might be easier for more
>> Model RRs to just buy themselves a 'cheap' PC and write a VB (or Bash
>> Script, depending on O/S) script.

> ??
> Unless I badly misunderstand the way DCC works, sending reversing
> commands to the loco isn't the right thing to do.  "Forward" and
> "backward" are determined strictly by which way the decoder is wired.
> I gather there's a few ways of handling loops under DCC, but they all
> basically work by detecting the polarity mismatch, and reversing the
> track feed -- not too different in principle to how it's done in DC.

> One obvious way, for the simple case of an end loop, is to feed loop
> power through the loop turnout.  When the train is completely in the
> loop, throw the turnout.  Loop polarity now matches the main at the
> exit point.

Is this:

  "http://www.ttx-dcc.com/technews/powershield_icb.htm"

what you are looking for?  In a reversing loop you don't want the
pick up wheels shorting out as it goes through the switch.  Flipping
the "polarity" in the rails should not affect DCC operationof the
loco.  

Paul
--
Working the Rockie Road of the G&PX

 
 
 

Auto-reversing for continuous operation of a point-to-point layout

Post by Stan Ame » Sat, 21 Jun 2003 04:14:19


Quote:

> We know of one device that automatically senses end-of-track and reverses
> the locomotive's direction, but we believe that it's for DC layouts only. Is
> there a similar device for DCC layouts?

Auto reversing is different with DCC but it is can easily be done.  I
have had a unit for years that does this.

In DC you reverse the polarity of the track.

In DCC you need to reverse the polarity of the locomotive.

What I have done is to put a detector at each end of the track and have
the detector control a relay. (same as DC)

The difference is that the relay controls the direction switch of a
handheld rather then the polarity of the track.  You set the address of
the locomotive in the handheld and the speed and functions work normally
but the direction switch in effect reverses as the locomotive trips the
detector.

Any detector works,  I have used both optical and current detection for
this purpose.

---------------------------

DCC Evangelist, DCC Book co-author, married to a DCC manufacturer rep
Home page with Disclosure Statement: http://www.dccsig.org/sra/

 
 
 

Auto-reversing for continuous operation of a point-to-point layout

Post by Paul Newhou » Sat, 21 Jun 2003 04:49:53




Quote:


>> We know of one device that automatically senses end-of-track and reverses
>> the locomotive's direction, but we believe that it's for DC layouts only. Is
>> there a similar device for DCC layouts?

> Auto reversing is different with DCC but it is can easily be done.  I
> have had a unit for years that does this.

> In DC you reverse the polarity of the track.

> In DCC you need to reverse the polarity of the locomotive.

> What I have done is to put a detector at each end of the track and have
> the detector control a relay. (same as DC)

> The difference is that the relay controls the direction switch of a
> handheld rather then the polarity of the track.  You set the address of
> the locomotive in the handheld and the speed and functions work normally
> but the direction switch in effect reverses as the locomotive trips the
> detector.

Way cool.  Can you point me at a How-To, a url or something, for the
excruciating details?

Thanks,
Paul

Quote:
> Any detector works,  I have used both optical and current detection for
> this purpose.

> ---------------------------

> DCC Evangelist, DCC Book co-author, married to a DCC manufacturer rep
> Home page with Disclosure Statement: http://www.dccsig.org/sra/

--
Working the Rockie Road of the G&PX