I am aware this was covered in a recent DCC Corner, and I am sure it has been covered here before, so just bear with me. Can someone explain what back EMF is? Some sort of dynamic braking for model locomotives? What does it do?
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Here's the technical definition of Back EMF:
http://en.wikipedia.org/wiki/Counter-electromotive_force
For purpose of our models, back EMF is used by a decoder to regulate the speed of a motor and keep the locomotive from speeding up as it goes downhill or slowing down as it goes uphill,
When back EMF is turned on, provided this is suported by the decoder, it acts as a governor to keep the motor turning at a steady pace regardless of the load placed upon it.
The simplest analogy is that back EMF acts like cruise control on your automobile.
This is how I usually find an answer to a question like this. Store the link you like in your Favorites folder for future use and maybe to help others in the future.
http://www.google.com/search?hl=en&q=dcc+back+emf&btnG=Search&aq=f&oq=&aqi=
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Thanks for the help.
So not all decoders support BEMF? Does a NCE DA-SR? Do I even need to bother if I dont have elevations?
BEMF is most often used for slow speed switching/running to help keep the locomotive drifting through trackwork. It is especially useful to smooth out the performance of steam locos in the lower speed ranges.
Do you need BEMF? Depends on what you run and how you want to run it. If you run steam and you are looking for "creepy" slow speed operation, then you might enjoy BEMF. I have BEMF enabled on several of my steam locos and it works quite well for slow speed operation. Others don't seem to benefit from it...The few diesels that I own run very smooth at slow speeds without it.
While it is accurate to describe BEMF as cruise control, most modelers I know don't use it to keep constant speeds when highballing on the main. It is more realistic to have the loco slow down as it works to climb a grade. Some decoders even have an option to fade the BEMF out at higher speeds to get rid of the "cruise control" effect on grades etc...And, as David pointed out, usually BEMF is not desirable when consisting.
My Two Cents,
Guy
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~Kyle
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