Top Speed Limit Question.

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Mountain
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Top Speed Limit Question.

Postby Mountain » Wed Oct 25, 2017 12:08 pm

Just a theoretical question.
In the past I've purchased two Digitrax decoders at a high price compared to other decoders, as they were programmable to restrict the locos top speed.
All my decoders I can alter the speed curves via my Lenz system. Now with the speed curve, is it possible to limit the top speed in this way for the decoders which do not have the ability to limit the top speed like the Digitrax decoders can?
It is just a theoretical question. I do not really have things set up to do my own testing at the moment and I've not really done much experimenting, other then alter the starting speeds and limit the top speed with the Digitrax fitted locos.
Enjoying 7mm narrow gauge.

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TimberSurf
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Re: Top Speed Limit Question.

Postby TimberSurf » Wed Oct 25, 2017 12:26 pm

I thought all decoders had V-Start, V-Mid, V-Max CV's as a minimum?
The more advanced decoders like the Digitrax have either many more CVs to program a "speed curve", or are capable of holding several "speed curves" that can be changed on the fly.
{not very experienced with DCC, but play with 3,000 CV's on industrial drives}
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Bigmet
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Re: Top Speed Limit Question.

Postby Bigmet » Wed Oct 25, 2017 3:08 pm

Unfortunately not. Manufacturers choose to leave out or poorly execute basic CV's and features which should be standard. Getting on fifteen years ago I tried examples of all the OO suitable decoders then available, and a particular gripe of mine was speed curves with a poor progression right in the mid range, just where they are going to be operating most of the time. Discarded as NBG. Other faults often found, unable to give a slow creep into and out of motion, rough or granular in low speed control, not able to maintain speed and/or accelerations stably, when compared on load and off load. Finally, one otherwise good decoder option simply didn't provide enough range in the CV's for the extended accelerations I require. That left just two makers.

I settled on the Lenz decoder range as my first choice because it had 'everything' required to control a good quality drive for the least money: the bonus - once the Standard decoder became available which must be seven or eight years ago now - all this came at budget price.

For 'difficult' mechanisms I use a few Zimos. More expensive, but you get more in CV options to beat the 'awkward customers' into submission. These decoders have moved from mechanism to mechanism over the years as the 'old clunkers' have been steadily replaced or upgraded. Zimo have recently joined the budget party with their MX600 family, making this brand a more attractive option.

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Mountain
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Re: Top Speed Limit Question.

Postby Mountain » Wed Oct 25, 2017 5:10 pm

Thanks for the answers. :) my decoders date from around 1999 to 2005 or there abouts. I have various Lenz along with Bachmann budget, and the two Digitrax. Only the Digitrax accept the CV that limits the top speed. Only a couple of locos I wanted them for, mainly the 03's and 08's, though some 08's of mine are already geared low. It is a strange thing not to have this feature on all decoders when all of mine have the starting voltage feature. With speed curves, it came to my mind that this could be possible. One could put the same value of speed at a certain position so the loco won't go any faster? I know it is theory. Was just wanting to know if this can be done in the real world.
Enjoying 7mm narrow gauge.

Bigmet
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Joined: Tue Aug 14, 2007 2:19 pm

Re: Top Speed Limit Question.

Postby Bigmet » Wed Oct 25, 2017 5:41 pm

If there is full speed curve access, then no problem at all. No need to limit the speed step range either, you just write in a curve across the full speed step range. I haven't had to do this with my 08s as the default speed curve was adjusted by making CV5 = approx 40, CV6 = half the CV5 value (range 0-255) and that produced a dead flat line in roughly two thirds of a mph increments per speed step, to a maximum scaling 20mph.

You must have pretty early Lenz decoders for them not to have CV5?

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Mountain
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Joined: Mon Oct 24, 2016 3:43 pm
Location: Somewhere in Wales, UK.

Re: Top Speed Limit Question.

Postby Mountain » Wed Oct 25, 2017 9:11 pm

Not early. Around 1999 to 2002 I guess most of them are.
Enjoying 7mm narrow gauge.


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