DC for 2 Rail THRU my Rev L TIU

 Hmmm, I think they all pass DC current when used as fixed. I have only used the two fixed with my DC on G scale. I believe they won't vary it. That's when you would use AC and the bridge to make it variable.

Bill,

So Q1.  Which TIU L channels will pass dc?  Fixed or variable?  If fixed only as I think I saw in the previous posts 

Only the Fixed channels will pass DC voltage.

Q2.  I think the only way to get variable DC when using a TIU  is to take a variable AC output and use a full wave rectifier to convert to unfiltered DC.  How about the need for a filter?

That is correct. However, I cannot comment on the need for a filter.

Q3.  Using whatever correct solution comes from the above what is involved in reversing the direction of a DC engine?  An external toggle switch?  It sounds too good to be true that there would be a way to do this with the DCS Remote.  But, hey, that'd really be great.

You can use an external relay triggered by an ACC port on an AIU to swap the plus and minus of the DC voltage to reverse the polarity of a DC engine. The external relay will get its own power from the output of the ACC port and will substitute for a DPDT switch that's got it's outputs reversed from each other.

Plus and Minus go into the relay inputs. The NC side of the relay has Plus and Minus  for forward, while the NO side has Minus and Plus for reverse. Both get connected to the tracks, however, only one pair is active at a time.

Barry, as always, thanks for the info.

  BTW is this covered in the Companion II? If yes where?  I couldn't find it but it was late when I looked.

Bill,

Unfortunately, it is not.

The DCS O Gauge Companion 2nd Edition, while very complete as regards 3-rail, AC operation, only addresses DC operation from the viewpoint of HO operators who are using a DCS Commander for DC power.

Thanks, Barry,

FWIW I can see why this topic is not in the DCS OGC II at this point.  It'd be 600 pages if you included every possible case. 

Barry is correct.  I use DC through a fixed channel my bench TIU to program locomotives.

Thanks, Marty,

So, what do you use DC for?  Based on all I've seen about your layout I thought you are a 100% 3 rail AC guy.  Am I missing some other use for DC here?

Bill, I use it for installing sound files in MTH locomotives.

I use the board from a Williams 3 rail loco, connected to the output of a variable channel, this gives me variable DC to control my my two rail loco's with my TIU remote. This was suggested to me by a fellow forum member, it works quite well.         Stephen          (cTr.....Choose the Right) & (There's power in serving)

Help me out here, The Williams reverse unit gets hooked up to AC on the output of a var channel and the motor leads would go to the track?

I suppose that would work  for one or 2 engines. Hey why not??

Marty,I've put lotsa command/sound packages in engines but have yet to edit sound files.  What advantage does DC offer if this is the right question to ask.  Thx, Bill

Bill,

According to MTH service, using DC voltage to power engines during sound file transfers will cause the transfers to be more error-free than otherwise.

My experiences have shown that, using both Rev. H2 and Rev. I TIUs, with a postwar KW for power, my transfers are about as error-free as I could ever want them to be. For me, using DC voltage would be an inconvenience with little, or no, discernible gain.

Stephen B, good idea.  If I have it right, most modern engines have DC operated can motors which are fed by the output of a full wave rectifier followed by (maybe, dunno for sure) some sort of filtering circuit to smooth out the rectified AC from the tracks. 

A neat way to do it for a DC engine or two.  Thx. 

Gregg.  Yes

That's good info if and when dealing with a situation. Thanks Barry.

I can see that the engine internal DCS boards would really like high quality filtered and maybe regulated DC power -- in the case of a marginal situation due to dirty power or data stream or a marginal board.

 Also takes the board's internal full wave rectifier out to the picture if I have it right. 

 Barry, if you're still here. You stated that only the fixed ch will pass DC. The variable channels set to fixed won't pass it then?? I've never tried it but I hoped I could use all four channels someday.

 Hmmm, I may go back to AC!! (on the G scale outback)

Joe,

You stated that only the fixed ch will pass DC. The variable channels set to fixed won't pass it then??

I know they won't pass DC in Variable mode. However, I'm uncertain of whether or not they'll pass DC in Fixed mode.

 Thank you Barry. I'll have to test that when I get time.

I do sound files very often and the DC is the only way to go in my book.

Marty,

I do sound files very often and the DC is the only way to go in my book.

You need a new book...  

Stop talking about one and write one for us.

Marty,

Stop talking about one and write one for us.

Been there, done that. You want another book??

OK, I'll see what I can do...  

Yes, we need another book.  Please stay with the same format and do not put a picture of yourself on the cover and people will buy it.

Well done on the current book.

and do not put a picture of yourself on the cover and people will buy it.

Put in a few jokes instead.

Oh, the abuse!