Soundtraxx Tsunami Slow Speed Tuning
A common complaint of
Soundtraxx Tsunami decoders, particularly the diesel decoders, is that they
have poor slow speed performance. Out
of the package, they will tend to ‘jerk’ a locomotive to a start, say 5 scale
MPH. Same for coming to a stop. But that does not mean they cannot run
smoothly. With a little tweaking, these
babies will let your loco run like they are gliding on silk!
So here
it is: Detlef's TSU Tuning Procedure:
1)
Make sure track and wheels are clean. None of this works without good
connection between the track and the loco. If you have trouble with this, don't
worry about BEMF tuning, get some help and come back when you have reliable
trains and track. (What is Back
EMF? Click HERE.)
2)
Shut off all momentum. CV3 = 0 and CV4 = 0
3)
I also start by enabling speed tables now, just with a straight line. This will
allow you to do speed trim later without having to come back to this: CV 25 = 2
and CV29 = 50.
4)
Probablly different from other's philosophies, I do tweak the motor control
sample period and aperture. There are strong opinions on this and it certainly
is not necessary. But I have mostly Athearn locos and it seems to do wonders
for them for slow speed control. CV 213 = 6 and CV 214 = 9.
Next
is setting the decoder’s PID control loop for managing the motor. Not sure what a PID control loop is or the
associated variables? Click HERE.
5)
Be sure CV 212 is set to 255 (default).
6)
Now, set CV209 to 0 and CV 210 to 0. The loco will not move.with these
settings. Don't worry, we will get there!
7)
OK, now the fun starts. Set your speed controller to speed step 1. Increment up
CV 209 one step at a time until the unit just starts to move. Admittedly, going
by 1's is a bit tedious, so I got to around 60 or 70 by 10's, then went by 5's,
and then by 1's.
8)
I then added some integral, CV210, until it started moving reliably when going
from speed step zero to one. I found all I needed was 2, 3 or 4.
9)
When you do this, you may find that speed at step 1 is too fast, so back down
on CV209 a bit, say 5 less.
10)
Then played with CV210 to get a good reliable start.
11) I found too much integral, CV210, was the main culprit for the 'cogging' effect. Back off and it does OK.
You now
should have a very smooth running loco. I have found, however, that a high CV 212
value will not allow locos to play well together. CV 212 'forces' the BEMF
control to keep the motor speed locked on a particular speed. If you are MU'ing
locos, even a small difference in motor speeds will tend to cause bucking and
rough operation. As such, I will typically back off CV212 to allow the motor
speed to drift slightly under load, allowing it to let go of load or pick up
load if another loco next to it it pushing or pulling more or less. I like a
value of between 120 and 150. Generally this will not affect the settings for
CV 209 and 210 much, but it may create a lag between when you go to speed step
1 and when the loco starts to move. If this bugs you, go back to the procedure
above and play with CV 209 and 210, or increase CV 212 until it is as you like
it. It's an iterative process meaning the more times you go through the steps,
the better you will be able to tune a particular loco. Typical values I end up
with are:
Speed tables radically
affect these settings, so if you want something other than a straight line
speed table, set it up front.
Now set your max forward and
reverse speeds with CV 66 and 95. And finally, go back to CV 3 and 4 and add
some momentum. If you don't like momentum much, choose a value like 15 or 20.
If you like more, well, that is a topic for another page!
ADDENDUM:
I have found this works for
MOST of my locos. But every so often
there are exceptions. There are other
procedures that work for tuning. One
very popular one is found at “Mr. DCC University” website:
http://www.mrdccu.com/curriculum/soundtraxx/tsunami.htm
Still, there is no magic
bullet for this tuning procedure. One I
recently did was an Athearn repower that used a Sagami motor. I tried my procedure, as well as the Mr DCC
procedure, and neither worked to my satisfaction. Yes, it got much better.
But it still had some hesitation on starting. Stay encouraged. It can
be a bit frustrating at first, but it is worth it. Just recently I MU’ed 3 locos, each with different decoders and
motors, all programmed with a lot of momentum and braking, and they all played
well together. It looked, sounded and
ran pretty nice!
ADDENDUM II: The MYSTERY CV
There is a CV217 out there,
not documented in the Soundtraxx literature.
Apparently it is a 'master switch' to turn on and off BEMF.
CV217=2 is BEMF On. CV217=0
is BEMF Off. Default value = 2
For what it's worth....
