I have two identical Athearn locomotives. The first is several years old and has a QSI Revolution sound decoder. I recently purchased a second locomotive and I want to install a sound decoder in it as well. The QSI is now producing the Titan decoder. I know that on my DCC home layout I can adjust different decoders to run together in a consist. However, I sometimes take my locomotives to the local club and run them on the DC layout. My question is, will different DCC decoders affect otherwise identical locomotives differently when they are running on a DC layout?
I suspect that since they are both QSI decoders, the way in whcih they address DC operation is more likely than not quite similar or the same. Theoretically, they both should simply let the DC simply pass through, but the way in which this is implemented could vary. My guess is that QSI, like most decoder manufacturers, shoots for maximum compatibility within its own product line.
Whatever is the case, can't hurt to try them to find out, confirming both are set to allow DC operation of course.
Mike Lehman
Urbana, IL
Try it to see.
The DC does "not" pass through a decoder. The microprocessor on the decoder senses DC or DCC and sends pulse power to the motor.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Rich,
I don't wear the EE pants in this household (the wife does) , so I tend to stay away from jargon that serves to obfuscate, rather than answer the question.
But since you're up on all the details, can you confirm whether the NMRA specifies the width and timing of the pulses? Or is that left up to the mfg, in which case you very well might get different performances on DC with different brands/models of decoders? That's what the OP wanted to know.
Most decoders are known as dual mode decoders, meaning they will run on DC as well as DCC without any modifications or CV adjustments. The decoder will sense the DC power and apply it to the motor and lights and some sound functions. If your loco was previously owned by another person they could have adjusted a CV value that shuts off the ability to run on DC but otherwise they should run well, although in my experiance they may run somewhat faster than on DCC. Whether they perform differently together could be a characteristic of the motor or drive linkage as well as differences in the decoders.
mlehman...can you confirm whether the NMRA specifies the width and timing of the pulses? Or is that left up to the mfg..
That is left up to the manuafacturers.
richg1998...The DC does "not" pass through a decoder. The microprocessor on the decoder senses DC or DCC and sends pulse power to the motor...
I do believe that at least some decoders, when they sense that they are on DC, do just open the H-bridge and allow the DC to pass through; however, there are also definitely some that pulse the motor when running on DC like they do on DCC.
That's a good question....
Since you are running DC and not speed steps, I would imagine any custom speed set up for speed matching are out of the cab window.That said, QSI has an analog mode where you can program analog start voltage and top voltage. If they are the same loco and both have QSI decoders you shouldn't have a big deal if the analog parameters are set the same.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
Don,
That's a good point. I know many of the DCC sound features in the Tsunami can be emulated in DC. In other words, you do need programming capability via DCC, but you can carry it away and operate on DC and use them. CV 63 and 64 control analog speed starting and max voltage. There is some other stuff that may be applicable in the User Guide.
The main thing that I am interested is when the 2 locomotives are running in DC mode they are as matched as they are in DCC mode. For the second locomotive I may use a non QSI sound decoder
Short of using the same decoder in both, or at leats the same brand, there's no guarantees. Even then, minor differences in manufacturing tolerances, etc can cause two otherwise identical locos to perform differently.
As I noted before, using another model of QSI decoder is your best bet. But if you can find one where you can set the analog min and max voltage, that will allow you to make adjustments to speed match the locos. I don't think you can rely on a match simply by using the default values in the decoders, as the mechnical differences may still be a factor. That's where having adjustments for the analog DC CV settings are useful. Of course, you'll need to use a DCC command station to set those correctly.