back emf decoder

[Mike]

Can someone simply explain the advantage of a back emf decoder, please.- Mike

[WoundedBear]

Think of it as "cruise control" for your locomotive.

If you are climbing a grade, the decoder senses the increased load and throttles up. It does the opposite on a down grade.

All it does is save you from having to manually maintain cruise speed....not so handy for a point to point layout, but has it's advantages for continuous running.

Sid

[Jim Banner]

A back emf decoder is rather like cruise control on an automobile.  It can even out speed changes going up grades and down.  This may or may not be an advantage.  Personally, I like to see a train slow down as it fights its way up grades.

Back emf control can also improve low speed performance.  When you start a locomotive without it, you often find that you must advance the throttle past the point of minimum running speed to get the locomotive to start.  Then you have to back the throttle off slightly to get really low speed running.  Back emf control can do this for you.  You set the throttle to minimum speed and the decoder advances the motor voltage until the train starts moving, then backs it off to minimum speed.  It won't make a silk purse out of a sow's ear, but it will make a good locomotive run better.

Just don't double head two locomotives with back emf control.  Inevitably, one locomotive will want to go faster than the other.  The faster locomotive will apply more and more power to keep the speed up while the slower locomotive will reduce power to get the speed down.  They can end up with the faster locomotive spinning its wheels while the slower one drags its wheels.

[Mike]

Thanks, guys. Very clear explanation.- Mike