A place to discuss Digital Command Control as well as give recommendations and reviews of D.C.C. Tech

Copy and pasted from the other thread:
I looked at the Gaugemaster decoders. I was going to look at the three they sell that have NMRA 8-pin harnesses but I ran out of time to do so, so I only have reviewed the DCC22 decoder.

The DCC22 decoder is similar to the DN136D decoder: a nice, simple decoder. The differences between the two decoders are: the Gaugemaster has a 0.5 amp increase in peak power (DCC22: 1.0A/2.0A peak, DN136D: 1.0A/1.5A peak), a smaller size (DCC22: 10.6 x 8.7 x 2.86mm, DN136D: 13.9mm x 10.3mm x 5mm), no Back-EMF (VERY useful for locomotives with poor motors or poor geartrains), and the DN136D has a hypothetical third function that takes some work to make available. The DCC22 is quite a bit more expensive, but if you need that extra half-amp that the Digitrax decoders cannot provide, the DCC22 is a better choice than the DN136D. If you need the room, consider getting a DZ126PS or even a DZ126T decoders, which provide less peak amperage but are a lot cheaper.

Gaugemaster DCC22: £24.95
Digitrax DN136D: £10.70
Digitrax DZ126PS: £12.23
Digitrax DZ126T: £15.29

4656942 How to install ditch lights

Back EMF explained:

Now, if you use DCC (Digital Command Control) you will have most likely seen some decoders advertised as having "Back-EMF", but you probably won't have known what it does.

Well there is a basic answer and a technical answer, depending on how in depth you want to go.

basic answer: Essentially Back-EMF is like a digital traction control, it means the locomotive is less likely to slip to a stand and they can pull off surprising feats of strength, such as a locomotive with the gears and motor from a slot car pulling 50 wagons.

Technical answer when a motor turns under power it generates a counter voltage that works against the current being supplied and is directly proportional to said currant, called back electromotive force. The higher the Back-EMF the more amps you need to keep it spinning, and the amp-draw will go up when it has to accelerate or is under strain, for example when a model locomotive is pulling a heavy load or ascending a grade.

A decoder can monitor the Back-EMF to work out the speed of the motor and govern the speed, applying more or less power when needed to ensure the motor turns at a constant speed.

One of the things this can be used for is to simulate the action of a governor. That is, trains go up and down grades while maintaining the same speed. Some people like this idea while others think it's a bad idea - it is NOT prototypical. Some people just want to see trains run and don't want to be bothered by continuously throttling up and down on grades. For layouts that are primarily used for display, this could be good - set the train's speed and let it run unattended. But for people who enjoy running their trains, prototypically or otherwise, this feature can take away from that enjoyment - for those, BEMF can be disabled while programming the decoder.

BEMF is used by sound decoders as well. For an internal combustion engine, it will simulate the load on the prime mover. Just like your car as you start from a stop, the engine will make noise proportional to the load, speed and throttle setting.

For external combustion, the BEMF is used to control the chuffs (or beats) of the engine under load, and the sounds like the rod clank that is heard during drifting. It simulates the effects of the throttle and cut-off, which are adjusted by the engineer as he brings the train from a stop to speed. The engineer would open the throttle and adjust the cut-off for maximum steam admission. As the engine begins to move and pick up speed, he will adjust the cut-off to reduce the amount of steam being admitted, like using a choke to richen or lean a mixture. The beats coming from the stack will change in intensity and duration in the process.

now there are some downsides, for instance when locomotives in a consist don't travel in the same direction or at the same speed they will begin to develop something called a push-me-pull-you effect, the faster one will pull harder whilst the slower one will hold back, until eventually you have one loco refusing to move and the other trying to go at full speed. Even if they are off by only 1/4 inch in 10 feet, it can be enough to get the syndrome started. And once started, it only intensifies.