DCC Idiots Guide

[doublepeg]

I am struggling to get my head around some of the terminology used in DCC, I have visited websites and followed links from this forum to sites that explain things in great detail but I can't understand what a lot of it means in layman's terms. For instance

 

"Acceleration Control", the way I understand it is the greater the number entered using my Elite the slower the acceleration, so what are "Speed Steps"? my Elite manual says the greater the number of speed steps the smoother the acceleration, isn't that the

 

same as "Acceleration Control" ? Then there is "Start Up Voltage", my Elite manual tells me there are 255 steps just like "Acceleration Control" as not all motors are the same and it may take several attempts to find the optimum, hopefully not 255 attempts,

 

is there a rule of thumb where to start with each particular type of motor or is it something that is going to keep me busy during the long winter evenings.

[poliss]

No, not the same. Acceleration control is like a car going from 0-60mph in so many seconds. Speeds steps would be the number of gear your car has. In the beginning decoders had 14 speed steps. No need to worry about speed steps these days as all decoders

 

have either 28 or 128 speed steps that never need to be adjusted. Just forget you ever read about them. :-)

Start up voltage. On DC control, you needed to turn the power knob up higher on certain locos to get them to start. On DCC you can alter the start

 

up voltage so that all locos start at the same setting of the control knob.

[Fishmanoz]

Acceleration control has an effect like inertia. Use a high number and the loco accelerates slowly and takes a long time to get to the speed you set. Low number and it gets to the speed quickly. And the same for deceleration control.

[Fishmanoz]

Remembering acceleration is rate of change of speed.

[Gregd99]

For me "speed steps" represent throttle settings rather than gears. 14 speed steps means the throttle can be set to 0%, 7%, 14%... I find that with my locos and decoders around 50% throttle setting represents scale max speed.

 

The general wisdom

 

seems to be that 128 steps give finer control but practically I find 14 steps is fine.

 

Acceleration control gives ayou a chance to make the operation of locos more realistic. In reality a loco starts up slowly as it needs to get a rake of wagons moving

 

along as well. I tend to have slowish start but relatively quick stopping. taking a metre to get to a reasonable speed looks good; often I need to stop faster than that!

 

have a look at http://www.nmra.org/standards/DCC/standards_rps/rp922.html#Descriptions%20of%20Configuration%20Variables%20for%20Multi-Function%20Decoders

 

for more info.

 

[Flashbang]

Hi

Think of Speed steps as being like to old dc controllers speed knob being turned. The further around the knob is turned the faster the train will move.

With DCC there are now three main speed step ranges 0 to 14. 0 to 28 and 0 to 128 available

 

(If the display is able to show the digits you will find 126 in the maximum, but thats another story). So selecting a speed step range with a higher step range allows finer control of the locos speed. In 14 speed steps the loco will move from rest to a fast

 

speed under what could be described as 'Course' range of speed controls in the 14 sets of step ranges available. In 28 speed steps the control is more finer as the knob is advanced through each of the 28 available step settings. By selecting 128 speed steps

 

the range of speed increase steps in now much finer and is over a total of 126 steps.

 

Acceleration is the time it takes a loco to move from stationary (or a speed its already running at below maximum) to the speed level now set by the speed

 

knobs setting. Say for an example from rest to maximum speed and the speed knob has been turned right up from 0 immediately. With a larger amount of acceleration set in the locos decoder the loco will initially not move, then slowly it will move off and increase

 

its speed gradually and slowly until a period of time has elapsed so that the loco is now running at its top speed. The idea is to simulate a real loco pulling away with a load behind it. It cant go from 0 to 90MPH in a couple of seconds, as the load its pulling

 

slows its acceleration down. Hence adjusting the acceleration rate of CV3 to a higher value number allows you to match the train load being pulled.

Deceleration rate is the reverse of the accelleration rate. i.e. the time it takes a loco to go from

 

whatever speed its travelling at to the chosen lower speed or stop. This is set by the CV4 value being increased for a larger (longer) period of slowing down.

 

With both CV3 and CV4 set to 0 (Zero) the loco is under direct and immediate control of the

 

consoles speed knob. Increase those values and the loco will become slower to accelerate or decelerate.

[Graskie]

Interesting. So, are you suggesting, Flash, that one should keep on changing rates of acceleration and deceleration according to what a loco's pulling (or even not pulling)? I'd never really thought about that. Makes sense, though.

[Gregd99]

if you want to be very realistic then re-calculating the accel/decel Cvs base don the train size/weight makes sense. I have been in some discussions where people suggested changing them while the train was running to reflect changed acceleration capabilities

 

from stop to mid speed versus mid to high speed!

 

personally I pick something that works and leave it alone. The elite's propensity to ignore commands form time to time focuses me on the most important commands being sent.

[2e0dtoeric]

I find that big red button in the side is handy for stopping things in a hurry! :-)

 

[doublepeg]

Thanks for the response guys, the fog is clearing somewhat. Acceleration control seems to be what I thought, the explanation of start up voltage is very logical and as for speed steps I think I'll forget I ever read it as advised.

 

Thanks again.