I mean, how does it synchronize with the movement of the loco? I'm not asking for a detailed electronic explanation, because it wouldn't understand it - just the basic principles involved.
One reason I'm asking is that I wonder if it's feasible to emulate the Surroundtraxx system which doesn't seem like it will ever get to market.
- Harry
The steam chuf sound is syncronized with the speed of a locomotve by a cam which is placed on the back of one of the driver wheels. If you go to the Digitrax web page you can download the instructions for their DCC sound decoders and it will give you instructions of how this is done. The instuctions can be downloaded for free.
Jim, Modeling the Kansas City Southern Lines in HO scale.
Yup some use a cam and some use an optical sensor. Both work fine. The more modern decoders also mix in the bemf to vary the intensity of the chuff when climbing hills, accelerating, or decelerating.
Springfield PA
Thanks. One more question: Do sound decoders have built in amps to drive the speakers?
As far as I know, the BLI Paragon series and the Tsunami decoders do not rely on a cam or on anything mechanical for their chuff synchronization. It may be an option, but it isn't necessary to get a 95% solution.
In the cases of QSI and Tsunami decoders that I use, they strictly rely on my using the Mark I eyeball to synch the chuffs at a nominal speed step, say 10, and then the decoder uses BEMF as a changing metric to vary the rate based on the BEMF as speed steps are changed.
I have learned via observation that a cold locomotive will chuff at a different rate set electronically than will the same locomotive after maybe five minutes of operation. Once they get warm, they get smoother and less demanding of power...or so it must be apparently. If I set the rate using the programming when an engine has been working for a while, I know immediately that it is out noticeably when I first run that same engine during a later operating session.
-Crandell
The Tsunami I recently installed has a chuff rate that increases with speed step, by default. It also has a wire which can be connected to a cam mechanism for true synchronization with the mechanical motion of the wheels.
While the cam may be used, it's not necessary. With all the other things I've got to do on my layout, this is one where I've declared the default chuff rate to be "good enough."
It takes an iron man to play with a toy iron horse.
The Tsunami's can run with or without a cam but depending on the loco it can be off quite a bit when running the auto chuff mode.
Page 19 and 26 show the cam options.
http://www.soundtraxx.com/manuals/tsuinstallation.pdf
Good info. Thanks.
- Matt k.
This is very good info, I've been thinking of purchasing a Bachmann Spectrum Consolidation and adding a Tsunami sound decoder, but wasnt sure how well you can sync up the drivers/wheels with the sound. Can you get it pretty close without a cam or other mechanical connection?
So far ALL of the different ones I've seen without cams do a very good job of syncing the chuffs. Some have been well configured right out of the box, others have required some tweaking of the chuff CVs to get them to look right. They key is at the lower end, when you cna easily see and count the wheel revolutions. Usually by half throttle or more you can;t really count the wheel revolutions so if it's close you're good, but at the low end when it's very obvious you should try to get it accurate.
--Randy
Modeling the Reading Railroad in the 1950's
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