Speaking of Easy DCC...

[Anonymous]

Hello Everyone;

I still use a conventional DC throttle for my small switching layout because I get great low-speed control from it, especially with my diesels. Would Easy DCC ( or any DCC, for that matter ) give that kind of control to the user? Right around that 5MPH and under speed range is important for nudging a car into a siding and I'm getting that with my cheapo MRC unit, but it'd be great to use more than one engine.

Many Thanks,
smyers

[SteelMonsters]

I've never used Easy DCC, but every DCC I've used (Digitrax, NCE, Systemone) have better control at low speeds. For one thing, there is an option called kick start that varies the length of full voltage applied to get the motor started. It basically reduces the hysteresis from stopping power and stopping power. It's adjustable so you can get the same charactoristics of a DC power, if you overcompensate, the loco will jump as you give it power.

Another option is playing around with the speed tables. You can get it so you have more speed steps in the lower region for better speed control at slow speed.

[Anonymous]

What you want is BEMF. This is the way to go for slow speed operation. It is a feature of many decoders in DCC. What it does is check the rotation of the motor and adjust the voltage supplied to keep it at a constant speed. Many people think that its use for controlling speed on hills. While that is one use, to me its main advantage is in making locos creep reliably. Any DCC system will be able to offer this. Once you experience it ,you will never go back. I can make a Proto 2-8-8-2 creep so slow with BEMFthat you have to look twice to make sure its moving.

[SteelMonsters]

I haven't used Back EMF decoders yet, but I want to try them out.

[Anonymous]

Thanks, everybody.
Back EMF is not a DCC scenario, but rather a decoder one, is that correct?

smyers

[Anonymous]

Decoders that use DCC can be BEMF equipped. You are correct if you mean that the BEMF feature is contained in the decoder, not the command system. It is all DCC, you won't find BEMF on straight DC.

Remember that DCC systems have several components, There is the command station and throttle system (Lenz, NCE, CVP, Easy DCC,Digitrax, etc) and these send signals and power to the track. Then there is the decoder. It is inside the locomotive . it receives the signals from the command station and runs the loco. Different brands of decoders will work with different brands of control stations thanks to the DCC standards established by the NMRA. Different decoders offer a variety of features such as BEMF, sound, dither, lighting effects etc. Google Loys Toys and Tony's Train exchange for online primers about DCC.

[SteelMonsters]

CEMF or Counter electomotive force is produced by all motors. Basically it is a voltage that counters the voltage source to lower current draw. It's also proportional to the speed of the motor. An ideal motor with no friction will have a CEMF of the same voltage as the source meaning 0 current draw. This is also full speed. As you load the motor down with friction or mechanical work it slows the motor down decreasing the CEMF and as a result current increases. Stalling the motor will result in 0 CEMF and the current will be in line with voltage and the coil's resistance.

Basically a BEMF decoder reads the CEMF and sets the total power the motor recieves in reference to the CV's.

So yes, BEMF is a decoder thing.

[ericboone]

Actually, there is no reason Back EMF could not be part of a standard DC throttle. I don't know off hand if one exsists, but I would not be suprised. Although the description on MRC's web page of their "Accutec" technology sounds an awful lot like Back EMF.
http://www.modelrectifier.com/products/trainSound/tech4.asp