Hi,
I'm attempting to speed match two units (Stewarts) and will work with cv02 (start voltage) and cv03 (acceleration). Its been a while since I've done this and can't find the reference to the values of each cv. My questions are:
CV02 - what is the value range and which is a low voltage start?
CV03 - what is the value range and which is a faster acceleration?
Thank you for any info!
Ooops, may I add - one decoder Digitrax, the other is soundtraxx. My DCC system is Digitrax.
ENJOY !
Mobilman44
Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central
This time, the CVs are fairly standardized - CV2 and CV3 are specified by the NMRA, although some decoder brands used different ranges.
CV2, the lower the value, the lower the start voltage. 0 means minimum setting. Values usually are 0-255.
CV3, the lower, the less momentum for acceleration (CV4 is used for deceleration, so if you set CV3 but not CV4, the loco will take time to reach the dialed speed, but if you shut it off, it will stop instantly). Default is usually 0 (some use a default of 1). The bigger the value, the longer it will take to reach the set speed. Digitrax decoder manual has the calculation for their decoders, others will usually indicate the forumla the use, in a form of for every X value in CV3, it will take Y seconds per speed step to accelerate to that speed step. Some go up to 255, Loksound for one goes to 32 (large values are well beyond what is practical - how often do you really need it to take 5+ second between speed steps - that means if you are starting from a stop and trying to get to speed step 50, it would take 250 seconds to reach that speed. Some momentum is nice with sound decoders, it allows the prime mover to "load up" before the train moves. The sound is usually not subject to the momentum, so if you are simulating a heavy train, you can crank the throttle, the prime mover will rev up but the loco will only start to creep and gradually speed up using the momentum rate iin CV3. As the loco reaches the set speed, the prime mover kicks back down. At the same time, if you turn the speed knob slowly, the loco will gradually increase speed without revving the prime mover - like when a light loco moves off. Tsunamis don't really do this, but the others do. The nice thing is you don;t have to reprogram CV3 for a light train or a heavy train, you can keep it set at a decent value and control the operation with your use of the throttle knob.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Note that to match them, you might want to leave CV3 alone. Set them to the same address, or just dial one up on the left knob and one on the right knob, NOT coupled together. Set them both at speed step 1. If one moves but the other doesn't, start using Ops Mode to set CV2 on the one that doesn't move. Start with 1 or 2. At medium speed, you can adjust eh DIgitrax one with CV6. The Tsunami won;t have CV6 for mid speed. Digitrax uses 0-255 as a range for these CVs, so 127 would be the speed it goes at half throttle with CV6 at 0. A lesser value will slow it down, a higher value will speed it up. And then at full throttle - this is controlled by CV5 (but is not on a Tsunami). No setting (default 0) is the same as putting 255 in CV5. A lower number will slow it down - so if the Digitrax one is faster, you can slow it down. Otherwise - time to look at 28 step speed tables, which both decoders will support.
Remember they don;t have to be perfect, just close. As long as you aren;t getting one unit dragging its wheels or one spinning, it will probably be fine, especially with a train hooked on. I have a pair of Geeps with TCS motor decoders coupled to an Atlas Trainmaster with a QSI decoder and the only setting I did was to make them all the same address (we don't allow consisting on the club layout) and set the lights up so only the headlight of the lead Geep comes on in forward and only the headlight of the trailing Geep comes on in reverse. I made no speed CV changes. These 3 run together for hours at a time with no issues.
Randy, thank you for the info! Its been a couple years since I had to to this and while I have notes, I can't find them.
I'll do some work on them now, and will come back when I get them acceptable. The thing is, the two locos have different motors, and thus different responses to the throttle.
Hi again,
Well, I could work with the B unit but the A was not responsive. Being familiar with Stewart locos, I felt the B unit was acting more normal in starting and acceleration whereas the B was late moving and slower.
For grins I looked up the NCE decoder that worked with Stewart FTs and it is a D13SRP - which I happened to have on hand. I switched out decoders and now the locos are both pretty much in sync. IMO, the Digitrax had somehow been compromised and was not responding as it should.
Whew, I think all is well and again thank you for the guidance!
I usually set both engines to the same address. I put one on the track and adjust it to the way I want it. It becomes the master for the consist setup. Then I put a second engine on a track along side the master. ( I use two trackes in a yard ) I change the CV settings in the second engine until it matches the master, or is close.
South Penn
South Penn,
In the past, that was what I did - test and adjust on the layout itself. Because these were so far apart I did the work on the test bench, the thought being to get them close and then move to the layout for final adjustment.
Which Digitrax decoder was in the one? If it was a DH123, that's an older low end decoder with no BEMF, while the Tsunami has BEMF (even if it isn't the greatest). The D13SR has a better non-BEMF motor control.
I have an AB set of FTs, drawbar coupled, one had a Tsunami and one had a TCS T1 (also BEMF) and they ran fine tied together with no adjustments. I traded the Tsunami one for a Loksound one, still run together and I never made any CV adjustments to either one.
Randy, the "original" decoder was a Digitrax DH123 (wrapped in blue plastic). The newer NCE is a definite improvement.