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| | |-+  BEMF/CV 10 HO MOGUL HESITATION QUESTION
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Author Topic: BEMF/CV 10 HO MOGUL HESITATION QUESTION  (Read 2260 times)
MarkInLA

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« on: August 21, 2012, 10:54:58 PM »

Hi, I recently had Bachmann replace a brand new faulty HO Mogul..2nd one is MUCH, much better but has a slight balkiness. Others have stated their's run perfectly...Someone suggested to try changing the BEMF,CV 10...I tried this with random values large and small but all she did was freeze up..I then had to do a 'system refresh' or other to get her back....Exactly what is the BEMF ? And is this correct, to change CV 10 value to smoothen out performance ? If not, I suppose I'll have to replace this one, too ! 
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jward


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« Reply #1 on: August 22, 2012, 10:48:11 AM »

bemf, also called back emf, is the oppositional force generated by any revolving electrical  gear. in this case it is a motor. most people don't know that any motor generates electical current as it is turning. turn the motor by hand and you should be able to measure this current. that is back emf.

in better decoders, this back emf is fed back to the motor control circuit, and tends to smooth out small variations in speed. thus, in model railroad use, bemf is similar to cruise control.

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Jeffery S Ward Sr
Pittsburgh, PA
bmjcook

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« Reply #2 on: August 22, 2012, 03:09:33 PM »



  Gidday
               Do Bachmann decoders have BEMF??  I think the Bachmann Tsunami sound decoders have BEMF. As stated elsewhere, we need to know what decoder is installed in loco.....Cookie
                                                                           
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GN.2-6-8-0


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« Reply #3 on: August 22, 2012, 04:15:21 PM »

All bachmann steam with factory sound have soundtrax tsunami decoders therefor BEMF.
« Last Edit: August 22, 2012, 04:20:22 PM by GN.2-6-8-0 » Logged

Rocky Lives
MarkInLA

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« Reply #4 on: August 22, 2012, 11:04:30 PM »



  Gidday
               Do Bachmann decoders have BEMF??  I think the Bachmann Tsunami sound decoders have BEMF. As stated elsewhere, we need to know what decoder is installed in loco.....Cookie
                                                                           
Cookie, as stated by another all Bachs have Tsunami/sountraxx and BEMF. I will try setting CV 10 to 1 or 0 values and see what occurs. If mogul is still eratic I probably will send it to Bach again ( this one is a replacement for 1st one which had a drivetrain problem)....Thanks for your help .. Mark   
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MarkInLA

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« Reply #5 on: August 27, 2012, 10:39:54 PM »

Hey gang, I changed  CV 10 to zero and mogul is running A-1 !! I  AM curious as to why Bachmann ( I'd suppose, as I didn't) gives CV 10 a 1 value ..If I didn't consult the group or other MRR forum I'd never had known to do this and would simply chalk it up to being an inferior product..Why doesn't Bachmann make note of this in the loco packages ? Or did I miss something ? How many, perhaps a thousand mogul owners are running the engine and just assume it's either faulty or don't even notice...or find out its in the decoder and not a mechanical problem..Even I was on the edge of returning the engine until I found out about CV 10...
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Len

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« Reply #6 on: August 28, 2012, 01:59:12 PM »

There's some good info on BEMF & PID here:

http://www.tonystrains.com/technews/introto_bemf_pid.htm

Quote
SoundTraxx Tsunami

The new Tsunami has a number of CVs related to PID control. They are Kp, Ki, and Kd. There are two more that are used to control the length of time or widow when to sample the Back-EMF voltage. The information on these can be found in the manuals for the Tsunami. The Steam Sound Userís Guide on page 57 to 60 is information on setting up the Hyperdrive. In the Technical Reference on page 90 to 94 shows information about CVs 209 to 214 for the Advance Motor Control Features. All of these manual are downloadable from SoundTraxx.

Tusnami Steam Users Guide: http://www.soundtraxx.com/manuals/tsunamisteam_users_guide.pdf

Tsunami Steam Technical Reference: http://www.soundtraxx.com/manuals/tsutechreference.pdf

Len
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If at first you don't succeed, throw it in the spare parts box.
wjstix

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« Reply #7 on: August 31, 2012, 05:39:46 PM »

If it's a new engine, it's more likely it just isn't broken in yet. I try to run a new engine on a continous run loop for 10-15 min. forward, then 10-15 min in reverse at about 3/4 full power when I first get them.

BEMF is Back Electro-Motive Force. When a motor spins, it uses electricity, but it also generates a tiny amount of electricity. This electricity it generates can be used to measure how fast the motor is turning. In a model railroad decoder, it measures the BEMF and uses that info to increase or decrease the amount of power going to the motor, so that the motor keeps spinning at the same rate. Because of that, the engine will run uphill and downhill the same speed that it runs on level track.
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