Is the maximum speed step a command station can send speed-step 126?
Yep. And the max speed in sMPH will be differ for every locomotive. It's primarily contingent on several factors like motor RPM rating, gearing, and lubrication.
A BLI SW7 I own goes a whopping 20sMPH at speed step 126 while my new Con-Cor Pioneer Zephyr will probably do near 80sMPH on the same setting. I generally do not dial up the speed step on my Power Cab for any of my locomotives higher than 80 or 90. That's usually close to or already at prototype speed.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
For DC layouts, we simply set the control knob at 11, which is, of course, much faster and louder than is mere 10.
Wayne
tstage Yep. And the max speed in sMPH will be differ for every locomotive. It's primarily contingent on several factors like motor RPM rating, gearing, and lubrication. Tom
Well, no. Or maybe. Not sure what the question is.
First, I believe there are 128 speed steps, not 126.
That aside, the statement that the maximum speed in sMPH will be different for every loco is generally correct, except that "every" is a strong word and assumes that there are not two or more locos with identical attributes.
This also aside, speed step 128 will not necessarily result in the maximum loco speed since it is possible to program the decoder speed step CVs (the speed curves) such that the maximum speed is obtained somewhere other than speed step 128.
Why anyone would want to do this is another question, other than to annoy someone else and make them go home and to find position 11 on a 10 position knob.
Hello All,
To put it simply digital is a language of "0" or "1" or "+" "-" in two states.
It is represented in numeric form in steps of 2, 4, 8, 16, 32, 64, 128, 256, 512, etc...
DCC signal can use the resolution of 14, 28, or 126 (technically 128). On my NCE throttle it even lists 28/128, as an option; bottom row, third button from left.
However many speed steps you choose on your throttle they are all relative.
For example:
I you choose 14 Speed Steps, 50% of 14 is 7, which means when you run speed step 7 the controller is telling the decoder to run at 50%.
At 28 Speed Steps, 50% of 28 is 14. Running at this setting 14 speed steps equates to a setting of 7 in 14 speed steps.
Using 126 Speed steps (accepting that it's actually digitally 128) setting your throttle to 64 is again 50%.
OK, so what's the big diff!?!
It's referred to as "Resolution." This can also be thought of as slices of a pizza.
When a pizza is cut into segments the size of the pizza does not change.
It's like the old joke...
A guy walks into a pizza shop and asks... "How many slices are in your medium pizza? "The counter person replied, "Eight." The customer says, "I'm not that hungry can you slice it into four?"
The number of "Speed Steps" on the throttle are only a percentage of the value selected, not the actual output of the booster.
DCC doesn't actually work that way, but for the sake of simplicity, I will keep using this example...
Whether you choose 14, 28, or 126 speed steps, the "maximum" value of each of these translates to 100% "power" to the given locomotive. (This is determined by the architecture of the decoder).
Unless you have adjusted the CVs that affect speed or changed the speed table, no matter the highest number of your throttle that's as fast as it will run.
So why choose one over the other?
Going back to the pizza example...
If I cut that same pizza into 16, 32 or 64- -see the numeric progression- -I can choose smaller segments.
These smaller segments of resolution with the DCC signal help when you are looking at slower, finer, movements.
One notch on a 14 speed step throttle equals approximately 9 notches in 126 speed steps. (I think I got the math right).
This more finite control can come in handy when switching, but not so much on mainline motive power.
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
maxmanFirst, I believe there are 128 speed steps, not 126.
Believe it, if you may, maxman. My Power Cab only goes up to 126.
maxmanThat aside, the statement that the maximum speed in sMPH will be different for every loco is generally correct, except that "every" is a strong word and assumes that there are not two or more locos with identical attributes.
Well, I think the word "identical" is equally strong. No two locomotives are going to have "identical" attributes. They could be very close but may differ slightly from one another. Perhaps that is splitting hairs?
maxmanThis also aside, speed step 128 will not necessarily result in the maximum loco speed since it is possible to program the decoder speed step CVs (the speed curves) such that the maximum speed is obtained somewhere other than speed step 128.
Agreed. But that speed curve will never be bell shaped so 126 will equal the fastest speed - whether it's achieved @ 126...or earlier.
Have we covered all the nit-picking yet? Okay, back to the OPs query...
passenger1955 Is the maximum speed step a command station can send speed-step 126?
Already answered, yes, but now for the why: The "128" step speed command uses 7 bits to produce 0-127. 0 = Stop and 1 = Emergency Stop (immediately stop without using decelerartion values), which leaves 2-127 for the 126 actual speed steps. The odd thing about the naming convention is the 14 and 28 speed step commands truly are 14 and 28 speed steps. For example, the 14 step command uses 4 bits to produce 0-15. You have the same convention with 0 = Stop and 1 = Emergency Stop, leaving 2-15 for the 14 speed steps. The 28 step command adds one bit for 0-31, but it doubles up the Stop and Emergency Stop (this is so that if the command station and decoder are not set the same the Stop and Emergency Stop still work), so you have a total of 28 speed steps instead of the 30 it would be otherwise.
There are 128 speed steps, but two are used for Stop functions, so you are left with 126 discrete values between minimum and maximum speed.
Speed Steps
A person can learn sumthin' each day here. Thanks, gentlemen.
doctorwayne For DC layouts, we simply set the control knob at 11, which is, of course, much faster and louder than is mere 10. Wayne
Good one Wayne!
maxman Why anyone would want to do this is another question, other than to annoy someone else and make them go home and to find position 11 on a 10 position knob.
Agreed, as one can see the horrific devastation in this next clip. A power pack that goes up to 11, might not be such a good idea.
So if you do have it in your means, one must at least try to resist the temptation.
"KIDS DON'T TRY THIS AT HOME"
TF
Track fiddlerLaughLaughLaugh Good one Wayne!
I'm pleased that you were able to add the clip about it going to 11, as I was worried that many viewers might not have been aware of the source of my comment.
doctorwayne Track fiddler LaughLaughLaugh Good one Wayne! I'm pleased that you were able to add the clip about it going to 11, as I was worried that many viewers might not have been aware of the source of my comment. Wayne
Track fiddler LaughLaughLaugh Good one Wayne!
There was never the slightest doubt in my mind where you were going with that one Wayne. One of my all-time favorites. Sometimes that dry English humor is simply the Best.