Ok, I had a troublesome 4-8-2 Bachman Spectrum that seemed to run at zero or warp speed on DCC (HO). So, after trying to adjust kick rate and timing, etc. I finally put in an extra Silver Lenz decoder I have, and WOW… now, she runs at speed step 1 of 128 and by step 2 or 3 she is as smooth as silk… I have to say, my first Silver line Decoder from Lenz with Back EMF (I have a ton NCE and Digitrax decoders) and I was way impressed…
What other decoders do you guys use with Back EMF? … doesn’t seem the same as torque compensation (TC) to me… just wondering what you guys use? Maybe I was just unable to get the TC just right…
I used a Lenz Gold (with BEMF) in my Stewart FT and it is absolutely my best crawler. (Course, Stewart’s are notoriously great runners anyhow.)
I don’t buy a decoder unless it has BEMF. When you locomotive starts out at 5 SMPH (or more), it just doesn’t look realistic. They are a must if you have switchers and/or a yard locomotives.
Version 7 QSI Chips have it. It has turned my rusted bricks into something that moves at one click of the DT400 throttle. As far as Im concerned, I only tolerate the older chips until I can upgrade and those do quite well too. If I buy decoders to install it must have this feature.
5-15 mph starts with the assoicated slack action is obselete.
Torque compensation is not the same as Bemf compensation. As far as I know, no NCE decoders have Bemf compensation. Most Digitrax decoders do have Bemf compensation, or what they call Scaleable Speed Stabilization, but they also have torque compensation, and if they have torque compensation, that does not neccessarily mean that they have Bemf compensation.
Yes Back EMF is a just the ticket for poor running locos…I found that out from a friend as he smooth out a old Athearn BB SD45.This SD45 was a average BB runner for its 22 years but,that Back EMF really smooth that old gal out.I was impress to say the least.
Back electromotive force. The emf that opposes the normal flow of current in a circuit. Not an electrical engineer, but assume this opposing force smooths out the motion of the motor in either direction, by its opposite energy. Any electrical engineers out there who can expand or better explain how it operates?
Back electromotive force (BEMF) is voltage that occurs in electric motors where there is relative motion between the armature of the motor and the external magnetic field. This is used in model locomotives to control slow speed operation, maintain speed on grades where gravity would otherwise slow or speed up the train and to determine the speed of the loco, i.e. speedometer.
BEMF is Back electromotive force. A DCC decoder controls the speed of the motor by pulsing the power and varying the amount of time the power is on. When the power is off, the motor acts like a generator. All decoder and motor combinations produce bemf. Decoders that have bemf compensation measure the voltage that the motor produces during the power off phase and adjusts the length of the power on phase to try to maintain a constant speed.
When an electric motor spins, it both uses electricity and generates (a slight) amount of electricity. The generated electricity is Back-EMF. As the speed of the rotating electric motor changes, the electricity generated changes. By measuring the electicity generated, a decoder can be set to increase or decrease the amount of electricity being fed to the electric motor in response to the change, so it always spins at the same rate.
It’s like “cruise control” in your car - it gives your car’s engine a little more gas going uphill, applies the brakes slightly going downhill, so you’re always going at the same speed. The decoder in the loco senses when the amount of electricity generated decreases (like going uphill) and sends more power from the track (which is a constant 14v AC) to the motor to compensate and keep it running the same speed.
BTW for most electrical / electronic engineers, Back EMF is a bad thing from what I understand…
What Back EMF can do is smooth out the running characteristics of engines that are greatly affected by grades. For example, my old Athearn F7 runs pretty well on level track, but would slow way down going uphill, and speed up considerably going downhill. With a BEMF decoder in it, I can set it at a moderate rate of speed and it will run at the same speed going uphill, downhill, or on level track.
As with any decoder, you can also change the top speed, so a DC engine that goes 110 MPH at full throttle will now go say 50 MPH or 40 MPH or whatever top speed you want, and allows you speed match it to other engines. I have a Kato SD-38 and an Athearn SD-38 and was able fairly easily to speed-match them so they run together virtually like one unit.
The problem is if you have two (or more) engines that both have BEMF. Let’s say you put two engines together, but the lead engine run slightly faster than the other. As the train starts to move, the lead engine begins to drag the following engine a little. The decoder senses this and assume the engine must be going uphill and need more power, so it increases power to the lead engine, making it go faster. However, the 2nd engine feels the pull and increased speed and assumes it’s going downhill and needs to slow up to keep running at the same speed, so it slows down to compensate. This of course makes the lead engine feel even more drag, and it tries to speed up even more to compensate. It keeps going around and around like that.
The solution would be to either not run two BEMF decoder-equipped engines together, or it might help to adjust the settings…most BEMF decoders allow you to set the in