EZ Command DCC Loco speed

[db22]

I have an EZ Command DCC controller and an EZ Command Dynamis controller and the same loco will operate at different speeds with each controller. The DCC 2-6-6-2 (with sound) runs faster under the basic EZ controller than it does under EZ Command Dynamis controller and, obviously, the loco has the CV's programmed the same for each test.
My test is with both controllers flat out. I do not, however, notice any difference in the chuff rate. The Dynamis shows 126/126 for velocity and the EZ is full clock on the control. I guess the thing to do is measure the voltage at the track but I do not have a dvm for the DCC reading. Has anybody got any theories or ideas as to why this is happening?

[scrimshaw]

I have noticed the same thing, My engines seem to run slower on the dynamis than they did on the EZ command.  I have only had the Dynamis for a few days and have not been able to play with it much.  Also, I have only ran two seperate engines, I will test some of my other engines this weekend.

[Jim Banner]

The voltage that the decoder feeds to the motor in a DCC on-board locomotive is a percentage of the DCC voltage on the rails.  The percentage is established by the throttle setting and does not depend on track voltage.  So if the track voltage is higher (as it is with the E-Z Command) then the locomotive will run faster.  If the voltage is lower (as it is with the Dynamis) then the locomotive will run slower.

Jim

[hotrainlover]

Jim,
Why is the voltage lower on the Dymus system, and NOT the EZ??  I think it would be the other way around...

[Tylerf]

The current should be higher on the dynamis which let's you run more locos. Voltage is how fast it will run, a lower voltage makes for better slow speed running.

[Jim Banner]

Jim,
Why is the voltage lower on the Dymus system, and NOT the EZ??  I think it would be the other way around...

Perhaps the Dynamis has a built in voltage regulator to keep the output voltage constant as the input voltage and track load change.  I suspect the E-Z Command lacks such a voltage regulator and therefore allows track voltage to drop as the load increases.  If this is the case, then perhaps the designer set the voltage a bit higher for light loads (say one locomotive on the tracks) so that the voltage would still be high enough at full load (say four locomotives running at once.)  I say this as a sometime electronics designer, not as someone with first hand knowledge of the thought processes that went into the design of the E-Z Command or the Dynamis.

[db22]

My measurements confirm the findings: Dynamis = 13.3v at approx 6.X KHz, the EZ Command = 16.1V at approx same frequency. I have no idea why Bachmann decided to make the voltage so low on Dynamis and it's going to be tough to find out as this site and the USA customer Support have only just about acknowleged the fact that Dynamis exists. It's time to take the lid off of the Dynamis - Mr Bach man, a schematic would be useful?

[OkieRick]

db22, Jim, anyone...

If the Dynamis does have an output lower than that of the EZ, and there is no reason for me to doubt db22's measurement, will there be anything lost in the wireless transmission of instructions from the handheld controller to the receiver / powerpak and on to the track?

I can't understand the method to the madness of lowering the voltage of a wireless operations based controller.  Then again perhaps I'm not supposed to.


Rick

[Jim Banner]

The communications link from the hand held to the command station is independent of the track voltage.  DCC commands from the command station to the decoders could be lost if the track voltage was too low, below 6 volts or so depending on the decoder used.  To me, the question is not why the Dynamis is so low but rather why the E-Z Command is so high.

Jim

[db22]

But, to acheive the same velocity at a lower voltage then I have to draw more current because the horsepower needed to operate at X feet per second is a constant. To do that I would have to change the resistance of the motor and I can't do that so I can only change the voltage and, to my knowledge, I cant do that with either EZ command devices. I say EZ Command because the Dynamis is also called EZ Command and, of course, it is made by the same people - Bachmann. It would therefore stand to reason that the cheaper EZ would be upgraded by numerous clients to Dynamis but the upgrade exposes the lack of compatibility of the 2 products from the same company.
I also think that the Dynamis is a Bachmann branded solution conceived by an independant company and the compatibility issue was never addressed by the persons involved.
A solution would be a calibration adjustment on either or both devices to allow for operational equality between different NMRA compliant cabs or for Bachmann to allow owners access to the schematics so that they could be modified. After all, modifying is what makes this a hobby and not a project. Bob, you and others probably have the necessary expertise to modify these devices for the benefit of numerous people. If Bachmann would assist us then we would not have to reverse engineer from scratch.

[OkieRick]

I reread the Dynamis User Manual today while drinking my 4:00 coffee and snacking on Ritz crackers a can of smoked oysters.  At the end of the book it said to visit the Dynamis website - http://www.dynamisdcc.com - so I did.  It's located in the UK

I found the FAQ section to be most informative.  A forum there would be nice.

What is the power output?

Answer

Dynamis is supplied with a 2.5amp power supply at 15.5 Volts stabilized to the load being taken

What is the rating of the track power?

The voltage is stabilised at 15.5v ± 5%, with 2.3 amps of power.


Note: This information is dated from March 2007 to March 2008.

Visit www.dynamisdcc.com

Rick -

[train with no shame]

are you all checking the voltage with a digital or analog meter across the tracks . on the ez track nickel silver .on a fluke digital meter . i show 23.9 v using the ez commander . i got confused in searching and reading other post getting 16v and so on .that's when i stopped asking . when i would run 4 of my trains i showed a voltage drop of about .8 being right at 23v would i be better off checking it with an analog other than the digital . i want to upgrade my controller .and have read in previous post .that some controllers do operate with less track voltage .inturn like you say making your engines run slower... i changed my layout and can't run in both directions like i was . i have also checked the voltage around the layout and the voltage is the same .with no voltage drop .my separate upper 18" rad .is also run off the ez commander as well . i brought power from the terminal railer up to it . thanks mark f

[pdlethbridge]

Oh, I'm starting to get a headache from all this electrics theory

[train with no shame]

excuse me . i tested my engines .my sd-40-2 has an amp draw of .15 amps at full speed .70 ton switcher has .05 ,the ft-a   has .10 and the sd-40 has .10 . does the  ez commander, using euro voltage of 220v is the max amperage 2 amps operating .as with the u.s voltage of 120v with only 1 amp max. on the ez commander .before overloading it . i have often wondered this .

[Jim Banner]

I think we are going to give PD another headache.

First, the power line voltage has nothing to do with the E-Z Command output.  Its output is related to its input voltage and its input voltage is the same independent of power line voltage, assuming you are using the proper transformer for your line voltage.

Second, motors are not resistors.  While the torque produced is proportional to the current through a motor, the current is NOT proportional to the applied voltage, except in the special case where the current is pure dc and the motor is locked up.  Otherwise the current is proportional to the net voltage (the difference between the applied voltage and the back emf of the motor,) the load on the motor (including its own friction,) the duty cycle of the applied voltage (how long it is applied compared to how long it is cut off,) the temperature of the motor (which affects its resistance,) and the frequencies and their distribution in the applied voltage (assuming the applied voltage is other than pure dc.)  All of these factors are important in a motor used in one of our model locomotives, whether it is run on DCC or by a dc power pack.

Third, measuring DCC voltage on your tracks is not as straight forward as it might seem.  Most mechanical voltmeters measure average ac voltage and convert it to RMS voltage by rescaling the markings on the meter.  Most digital voltmeters measure the peak ac voltage and convert it to RMS by playing with the parameters of the analogue to digital conversion.  Both require that the waveform be pure sinusoidal to work properly.  Neither work properly with the rectangular waves put out by DCC.  True RMS voltmeters can read DCC voltages properly as can oscilloscopes but both require interpretation to figure out what the dc voltage applied to the inner workings of a decoder will be.  As far as your DCC equipped locomotive is concerned, that last voltage is the only one that matters.

If that doesn't have PD's head throbbing, this question will:
If 12 volts dc pulses with 50% duty cycle are applied to a resistor, what is the RMS voltage across the resistor?  What is the average voltage across it?  Now make that load a motor.  Will its speed correspond to the RMS voltage or to the average voltage?