It seems a lot of people don’t realize or don’t care that their Tsunami’s back emf is OFF by default. I was just wondering why.
Edit: By “off” I mean that the CV2 was set to non-zero and the Ki/Kp parameters not optimized. There is no “On/Off” setting per say.
For those of you who would like to setup your Tsunami Back-EMF and didn’t know it was off, here’s an excerpt from page 58 of the user’s manual:
[quote]
QUOTE:
Strategy for CV Optimization
Finding the right combination of CV settings requires a certain amount of
experimentation and patience to get the best performance. Be aware that
these settings will also vary from one locomotive to another. Take notes of
your CV settings so you can use them as starting points when configuring
other locomotives.
Overdoing a particular setting can actually degrade performance so
changes should be made in small increments (+/- 10 or so) until the desired
performance is attained. The default settings should provide satisfactory
performance when used with most HO and N scale motors.
We suggest the following procedure to help fine tune the CV settings:
Begin with each CV set to its default value: CV 10 = 0, CV 209 = 25, CV
210 = 20, and CV 212 = 255. In addition, set CV 2 (Vstart) to 0.
With the locomotive on level track, set the throttle to around speed step
Adjust the value in CV 209 (Kp) with increasingly higher values just until
you begin to notice some jerkiness in the locomotive speed. Reduce the
setting in CV 209 to the value just before the jerkiness started.
Adjust the value in CV 210 (Ki) with increasingly higher values until you
begin to notice some oscillation in the locomotive speed whenever the
throttle setting is changed. Reduce the setting in CV 210 to the value just
before the oscillation started.
My On30 Bachmann Outside Frame 2-8-0 ran great with the Lenz slug supplied with it. When I installed the Tsunami the performance was phenomanal and I have only played with the sound.
Back-EMF is regulated speed control of the motor. What that means is if you set a setting of “1 of 128” on your throttle is will run smoothly at speed 1 without intermittent stops. It also means that you maintain the same speed on hills, or after you attach a large lashup to an engine. Smooth low speed operations are essential to those doing switching action.
The decoder does this by measuring the Back Electro-Motive-Force (Back-EMF or BEMF) on the decoder. When a motor begins to stall/meet resistance, the current draw goes up. By monitoring shifts in current, the decoder can compensate for the load change and maintain a constant speed.
A number of decoders already do this including Lenz Gold and Silver, and Digitraxx. The tsunami has an excellent BEMF called Hyperdrive. However it requires a bit of extra setup to get running properly.
The usual thing I hear people raving about is for the very unprototypical thing of having a locomotive maintain a constant “speed” once the throttle is set, reguardless of the grade, curvature, or load. In my opinion, it is the engineer’s job to adjust the throttle to compensate for curvature and grades. With out that prototypical action what fun is running the train?
What I would like to see it used for is to change the exhaust tone and cut-off sound on steam locomotives to reflect if the locomotive is working hard or not. The old 1970-1980 PFM sound units had this feature and it really enhanced the “sound experience”.
I had not realized that I was obliged to configure the BEMF, but my IHC runs relatively well as it is. Also, it barks very nicely when I crack the throttle. Whenever I get a track up and running again (July?), I’ll be sure to play with those CV’s. Thanks for the information.
The Tsunami’s and the Upgraded QSI chips do have the automatic labored chuff sound for steam. The harder they pull the different the pitch/volume. It’s quite realistic especially when CVs 3 and 4 are set to 15 or higher.
Tsunami is even so smart that it will automatically sound the “grade change” whistle if it detects a change in motor resistance (when doing up/down a hill) This is an optional feature.
You can also adjust the level of compensation so that your loco slows down a bit on curves/grade changes with some decoders. The level of Back-EMF for higher speeds can be set to “0%” if you wish, and “100%” for lower speeds. This is a real boon for people who need their loco to crawl without stalling, but also don’t want compensation at higher speeds.