gregc DigitalGriffin Decoders can't measure the motors magnetic field. they don't need to. electromotive force is a voltage. the decoder measures the voltage produced by the motor with the drive circuit momentarily turned off. when a voltage is applied to the motor with it not turning (stalled), the current is limited by resistance. The currrent produces a force when in a magnetic field causing the motor to rotate. When the armature rotates in the magnetic field a voltage (EMF) is produced. This back EMF counters the voltage supplied by the decoder, reducing the current (Ohms law) and the force causing the armature to rotate. equilibrium is reached at some speed. If the speed decreases, the BEMF decreases, current increases and force increases. If speed increases, BEMF increases, current decreases and force decreases. the current varies with the load on the motor. The BEMF is proportional to speed and measurable. why would they call it BEMF if they are not measureing BEMF?
DigitalGriffin Decoders can't measure the motors magnetic field.
they don't need to. electromotive force is a voltage. the decoder measures the voltage produced by the motor with the drive circuit momentarily turned off.
when a voltage is applied to the motor with it not turning (stalled), the current is limited by resistance. The currrent produces a force when in a magnetic field causing the motor to rotate. When the armature rotates in the magnetic field a voltage (EMF) is produced.
This back EMF counters the voltage supplied by the decoder, reducing the current (Ohms law) and the force causing the armature to rotate. equilibrium is reached at some speed. If the speed decreases, the BEMF decreases, current increases and force increases. If speed increases, BEMF increases, current decreases and force decreases.
the current varies with the load on the motor. The BEMF is proportional to speed and measurable.
why would they call it BEMF if they are not measureing BEMF?
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
SouthPennThe BEMF calculation only gives you motor RPM. You still need to account for the gearbox ratio and wheel diameter.
yes. But measuring the speed of the motor is the hard part.
you could calculate and program a translation value into the decoder (and command the loco to run at a specified speed).
greg - Philadelphia & Reading / Reading
The BEMF calculation only gives you motor RPM. You still need to account for the gearbox ratio and wheel diameter.
DigitalGriffinDecoders can't measure the motors magnetic field.
gregc DigitalGriffin BEMF uses variations in the current. It is a little less accurate, but works. huh? From Counter-electromotive force The term back electromotive force is also commonly used to refer to the voltage that occurs in electric motors where there is relative motion between the armature and the magnetic field produced by the motor's field coils, thus also acting as a generator while running as a motor. This effect is not due to the motor's inductance but a separate phenomenon. This voltage is in series with and opposes the original applied voltage and is called "back-electromotive force" (by Lenz's law). With a lower overall voltage across motor's internal resistance as the motor turns faster, the current flowing into the motor decreases.[4] One practical application of this phenomenon is to indirectly measure motor speed and position, as the back-EMF is proportional to the rotational speed of the armature.[5] In motor control and robotics, back-EMF often refers most specifically to actually using the voltage generated by a spinning motor to infer the speed of the motor's rotation for use in better controlling the motor in specific ways.[6]
DigitalGriffin BEMF uses variations in the current. It is a little less accurate, but works.
huh? From Counter-electromotive force
The term back electromotive force is also commonly used to refer to the voltage that occurs in electric motors where there is relative motion between the armature and the magnetic field produced by the motor's field coils, thus also acting as a generator while running as a motor. This effect is not due to the motor's inductance but a separate phenomenon.
This voltage is in series with and opposes the original applied voltage and is called "back-electromotive force" (by Lenz's law). With a lower overall voltage across motor's internal resistance as the motor turns faster, the current flowing into the motor decreases.[4] One practical application of this phenomenon is to indirectly measure motor speed and position, as the back-EMF is proportional to the rotational speed of the armature.[5]
In motor control and robotics, back-EMF often refers most specifically to actually using the voltage generated by a spinning motor to infer the speed of the motor's rotation for use in better controlling the motor in specific ways.[6]
DigitalGriffinYour car would give a false reading on the speedometer too if it's wheels slipped.
rrinkerChip , you haven't been gone from PA THAT long to have forgotten about going 40 on the snow and ice and your car isn't actually moving.
I was refering to the sensors that govern speed and proxemity to obstacles and control automatic braking, cruising distance, and limits road-kill points in crosswalks, not to the cable that runs to the back of the dashboard.
Chip
Building the Rock Ridge Railroad with the slowest construction crew west of the Pecos.
Chip , you haven't been gone from PA THAT long to have forgotten about going 40 on the snow and ice and your car isn't actually moving.
Don - this is something I was thinking, but I have too many projects on my plate. WiThrottle protocol is best, it's simpler than Loconet plus it wil work with the Digitrax Wifi interface, the MRC wifi interface, and any other system, that works with JMRI.
My other idea would be something like a combination app and phone case, the app would display plain text buttons for functions, the case would incorporate a throttle knob that would interface via Bluetooth. If the part that fitted around the phone and the part holding the electronics and the knob would have some sort of physical connection, you could just make different case parts for different brands and models of phone without changing the expensive electronics part. Sort of like the ESU Cab Control throttle, but the screen part would be using your own smartphone, Android or iOS. Cost would be for the knob and BT interface, using the phone you already have. Also using WiThrottle protocol to make it universal.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
DigitalGriffinBEMF uses variations in the current. It is a little less accurate, but works.
SpaceMouse The decoder needs only to know the number of revolutions a wheel rotates (or the motor rpm) and translate it in speed using an input stored in a CV. That works as long as the wheels don't slip like when on a grade. Perhaps we could automobile technology to get a more acturate reading of speed and possibly stop the train if there were something in the track like a curious cat or a miniputean.
The decoder needs only to know the number of revolutions a wheel rotates (or the motor rpm) and translate it in speed using an input stored in a CV.
That works as long as the wheels don't slip like when on a grade. Perhaps we could automobile technology to get a more acturate reading of speed and possibly stop the train if there were something in the track like a curious cat or a miniputean.
Counter-electromotive force is proportional to motor speed and is measured by many decoders.
Couldn't a scaling value stored/set in the decoder be used to translate BEMF to scale speed?
Well when people tell me it can't be done and I know I can do it, I kind of take it as a personal challenge. I'm going to use the WiThrottle protocol, which I'm guessing is also compatible with LNWI. I'm reasonably certain I can do the loconet protocol and make it a plug in throttle. But first things first.I ordered the parts and already started a case on tinkercad. I'm making it open source. I'll start a thread when I have primary renderings done and look for feedback from the community. Expect a thread in two weeks.I'm adding tactile buttons, a screen, and optical encoder.
SouthPenn Khier I think having actual scale speed showing on the controller might be hard to do
Khier
I think having actual scale speed showing on the controller might be hard to do
I think having actual scale speed showing on the controller might be hard to do. The decoder would have to know the gear ratio and wheel size. ( even more CVs ) Also the exact motor RPM then do the math.
khier Graffen Railpro is a proprietary system. Too bad. I started to like the controller already. Walid
Graffen Railpro is a proprietary system.
Railpro is a proprietary system.
Too bad. I started to like the controller already.
Walid
RailPro runs on DCC systems. I have an NCE power pro system and I run RailPro on the same track at the same time.
I find that I run the RailPro engines a lot more often than the DCC engines. My plan was to only install RailPro in engines that had no decoders at all. That plan went out the window. I am slowly replacing my DCC decoders with RailPro.
Randy,
First and foremost my apology if my words and style seemed offensive or aggressive. Typed text creates a different impression than words spoken face to face.As for the speed feedback, I have never meant measuring the speed and sending back to the command station. All I meant a scaled indication of speed. Instead of 10%, 20%, 50%, 20, 40 and 100km/h if I set the maximum speed to 200 km/h.When you raised the speed feedback issue I responded with possibilites of how manufacturers and/or electornic freaks could easily introduce a speed it. It was a response to your point not mine.I fully understand your comments regarding the push bottons. Perhaps I could not express myself clearly. I said even for the 28 steps push bottons is something that belongs to the past.
Although I mentioned it earlier I will repeat it again: I am NOT trying to convince anyone what to like or dislike. I am NOT trying to tell anyone what is right or what is wrong. As I said before, there is neither right nor wrong in the hobby. Everyone uses what makes him/her feel comfortable and let him/her have fun. I do respect all opinions even those I disagree with. All I wanted is to hear what others think rather than to prove anything, but I had the feeling all the time that you are trying to prove a certain view.RegardsWalid
Walid, you should be a politician. ABsolutely noothing you replied on diagreed with anything I said. I'm an enginner. Perhaps you are too, or at least have a decent math background. So yes, for US it is "child's play" to calibrate speed. Though I don't think BEMF is the way to do this. I very much dislike BEMF levels that result in cruise control where the loco runs the same speed up and down hills, with 2 cars or 20. But what about the rest of the hobby population, who don't know all that? Yes, there are plenty of locos already out there that have either interrupter wheels or Hall sensors used to sync the chuffs. Don't think any diesels have that (except maybe MTH) since they don;t have anything to sync with the speed. But as already mentioned - there is no mechanism in DCC to get that information back to the THROTTLE. Railcom and Digitrax Transponding allow for this, but you have to be much more careful in wiring the layout for it to work completely reliably. The signal from the decoder is very tiny, because it is transmitted using stored energy, the command station uses a quiet time with no signal (and thus no power) to allow the decoder to signal back. Similar to the concept of X10 sending a signal at the zero crossing of the AC power for home automation.
But then the last one - perfect example of taking a quoite and cutting it off to make it out of context. I do NOT like pushbutton speed control. Never said I did. The idea of pushing a button up to 126 times to get to full throttle is just silly to me. What i SAID was, pushbuttons for speed control might be ok, if you only have 28 speed steps. NCE systems defult to using 28 speed steps for control. You can change to 128, but there is no way to make it default. Digitrax systems default to 128, but you can set it to default to 28 or even 14 if you really want to for some reason.
It all comes down to lack of interest - you're sure big on a better throttle, but obviously not enough people are. There's been nothing preventing anyone who wanted to from developing a completely different type of throttle for at least 10 years now. There's even been an open protocol that works with any DCC system that you can connect JMRI to. MRC, Digitrax, and ESU are using it with their latest devices. But it's been around for several years now. If there was such a demand for a better control unit, surely someone would have stepped in to make all the money just waiting out there. Plenty of people with the ability have done DIY units, and shown others how to replicate that. But no commercial interest. I think you greatly overestimate the size of the market. I too wish everyone were into model railroading, but the truth is, this is a rather small hobby. And DCC is just part of that. If you look back when DCC was first introduced, half the companies that were selling systems have evaporated. There were too many for the market to bear. If DCC vendors sold millions of systems a year like smartphones, then we would indeed have $50 throttles with color displays and every other usability aid. But they don't, so we don't.
gregc
Regards
khier SouthPenn This is what DCC should have evolved to by now.
SouthPenn This is what DCC should have evolved to by now.
This is what DCC should have evolved to by now.
If the manufacturer goes belly up, you have no way to buy parts for it.
A bit like DCS...
If you're going to invent a whole new system, get it NMRA certified, so it might be standardized...
Swedish Custom painter and model maker. My Website:
My Railroad
My Youtube:
Graff´s channel
And then you can alter a hand control to better suit your hands...
My ROCO Multimaus had a curved casing, but my big hands didn't like it.
I then designed and 3D printed my own.
I decorated it a bit to suit the timeframe I model.
It's all about user interface....
This throttle I use for most road engines.
DigitalGriffin Have you seen the home brew low cost DCC command stations using pi and arduino?
Have you seen the home brew low cost DCC command stations using pi and arduino?
DigitalGriffinWe're a small market. It represents a couple thousand unit sales a year I would imagine.
rrinker Until every loco has an encoder wheel to measure actual speed (and unless that is some mechanically calibrated device rubbing on the track, it will need to be calibrated in the decoder to convert RPM of the shaft to actual speed based on gear ratio and wheel diameter - you can;t shortcut this) and direct feedback (both the Lenz Railcom and Digitrax's Transponding have shortcomings, and even the direct radio systems that have nice 2 way communication with the loco receiver still need some mechanism to calibrate any sort of scale speed readout), the only way you have to make the throttle read scale speec is to calibrate each loco so the speed percentage of throttle shows the scale speed the loco is configured to run at.
First, all it takes is a magnet and a Hall effect sensor to make the encoder. The resulting pulses are fed back to the decoder. Multiply them by a cale factor and you have the speed. If my memory serves me well, some decoders are already prepared for that to sychronize the steam sound with the speed.Estimating the scaling factor is an easy assignment for a 6th grade pupil. Simply multiply the perimeter of the wheel by a the RPS you get the speed/second. The perimetr is 3.14*the diameter, which can be measured by a caliper. Use 3 if 3.14 is too complicated. Multiply the result by 3600 and devide by 1000000 (if you measure in mm) you get km/h. Scale it up by 87 you have the prototype speed, or leave it as it is to have the actual speed. The RPS is measured by the decoder by simple pin change interrupt, or rising/falling edge interrupts. Neither mechanically calibrated devices rubbing the track, nor rocket science involved.Another way to encode, make a black spot by CD marker on one of the wheels and fix an Tx/Rx sensor to generate the pulses. A teeth of a gear can be used instead. The gear ratio will have to be included then in the scaling factor. Count the number of teeth to deduce the gear ratio. Again not rocket science.
Lastly, BEMF is already used to adjust the speed. You can run the train for a fixed distane and the decoder measure the time needed to cover the distance to calibrate the scale speed. Also not rocket science. Want more suggestions??
rrinker Then they had to go ahead and make it 29 functions. No one wants an additional 10-15 buttons so that F0-F28
rrinkerButton pushing for speed is OK,
rrinkerand the whistle and so forth look obvious as well. But what is the button to the left of the direction, with the three horizontal lines? And what is the button to the right of the 3, with the array of boxes?
Four Months ago was the last time I actually held the thing and used it, but if memory serves, the three lines was menu. I dont remember what the button with 9 dots on it did.
The throttle has four soft keys across the top (if memory serves they are user selectable, and operate what is displayed above them on screen). I only played with it for a few minutes at the Amherst Show, but was sold on user comofort. My only request was for a small metal pin in a recess or similar capability to allow the throttle to clip to a lanyard.
DigitalGriffin Well I would consider the following nice to have dedicated buttons for Light (F0) Bell (F1) Horn/Whistle (F2) Coupler Clank (F3)Brakes (that work)Dynamic Brakes (that work)/ Cylinder blowdownThrottle/Effort UpThrottle/Effort DownDitch lightsThese are ALL common operations by REAL engineers. Yet NMRA never desginated common function buttons which are mapped all over the place between the big 4 (TCS/Loksound/Soundtraxx/QSI) It makes their operation cumbersome. And setting up consist is still a pain. Specifying which is lead, which is middle, which is rear, which is facing forward, or reverse.
Well I would consider the following nice to have dedicated buttons for
Light (F0)
Bell (F1)
Horn/Whistle (F2)
Coupler Clank (F3)Brakes (that work)Dynamic Brakes (that work)/ Cylinder blowdownThrottle/Effort UpThrottle/Effort DownDitch lightsThese are ALL common operations by REAL engineers. Yet NMRA never desginated common function buttons which are mapped all over the place between the big 4 (TCS/Loksound/Soundtraxx/QSI) It makes their operation cumbersome. And setting up consist is still a pain. Specifying which is lead, which is middle, which is rear, which is facing forward, or reverse.
You might want to check out the RaiPro controller. The latest upgrade ( free download ) has added a lot of new options. You will need RailPro decoders.
Want to do a consist? Press the 'link' button, select the engines you want in the consist ( the first engine you select is the lead engine ), press 'done'. If an engine needs to run in the opposite direction to match the consist, press the button labeled 'MU=' which will show up when you make up your consist ( the = will show how many engines are in the consist. ) on the MU= page select the engine you need change and press the direction arrow. That's it, done. Speed matching is done automatically. I have had nine engines in a consist and they ran fine. Having pushers or helpers that really push or help is great.
Actually, setting up a consist takes 20-30 seconds. Shorter than my write up.
From your description of the system you are using, the interface is far less friendly than many other existing DCC systems, let alone anything someone can actually imagine there being.
As for the TCS - I see a bunch of buttons with icons that I can't just figure out by looking at it. OK, maybe that makes it more "world compatible" vs having the buttons labeled in plain English. Many I can figure out - I've sure the <--> button is direction, and the whistle and so forth look obvious as well. But what is the button to the left of the direction, with the three horizontal lines? And what is the button to the right of the 3, with the array of boxes? Menu maybe?
The rest of is it very much following what anyone with some knowledge could do - they are usign existing protocols like WiThrottle over WiFi to connect the throttles to the command station. Not inventing something new and proprietary. This is where I think the guys with that nifty prototype control stand went wrong, they use an intermediate protocol and then need a second device to interface with various DCC systems, adding cost and complexity.
Button pushing for speed is OK, I guess, when you are using NCE and only have 28 steps. But most of the rest of the world seems to have changed to 128 steps as the default, and locos run demononstrably smoother - check the MR reviews where they test both 28 and 128, the same loco, no other change other than sending it 128 steps instead of 28, starts slower and sometimes has a more accurate top speed as well. Maybe this is why I do a whoel lot less fiddling with speed tables than some seem to? Because with a greater change per step, it takes more configuration to make them indentical between locos?
I do not know why the replies come as if I am advocating touch screens.
Gentlemen, advanced user-friendly user interface does not have to be a touch screen. It can be a combination of anything. The point is to be direct, easy and clear input/output, no click forever, no abbreviation, no botton combination, and of course, not for an arm and a leg.