Junctionmad

On 29/08/2021 at 20:11, Andymsa said:

1 hour ago, Ron Ron Ron said:

 

The thread that never ends...........

 

 

The thread that never ends...........

 

 

The thread that never ends...........

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Nobody forces you to read it so stop whinging 

17 hours ago, AndyID said:

 

Just my opinion but the way Ohm's Law is typically expressed (V over I equals R) doesn't quite get the message across. I think the problem is it does not bother to explain the basic algebra that allows the same law to be written three different ways. I'm tempted to think real problem has nothing to do with fundamental electronics; it's much more to do with fundamental math and lousy teaching methods.

 

There are a very few basic math rules to learn but if you don't grasp them many simple equations just look like a load of complete gobbledygook. I was fortunate to have a good teacher but I'm not sure I would ever have figured them out by myself had I not.

yes but the points is the computation for LEDS is simple the voltage dropped across the series resistor divided by the set current , NO laws , algebra etc 

if you can use a calculator you can get the resistor needed . ie Green led , 10V supply ( 10-2.5)/0.005  is no more difficult then that 

modern red green blue yellow leds will run down to 1mA these days  and upto about 30mA,  ( many will survive 60mA)  5mA is a good starting point, white leds are slightly different  

heres a quick summary of the major types 

looking at the layout measuring video its unclear how many magnets are being used .  It does seem that the loco can establish patterns upto 2 metre away but the recommended spacing is 20 - 100cm  

Hence I think ill modify my previous statements , It is capable of establishing multiple position detections , how many is not clear , if you look at the track measuring video  , you can see that you use a given loco to "walk " the  track on the mimic panel . measuring each section .  again whether this is by BEMF sensing or multiple magnetic field sensing is not clear .

Hence the system is more capable then a single point spot detection 

again its not clear if the positioning is continuous or a series of discrete points 

whats clear is that with magnets  min 20-100cm apart that's a lot of reference points on a layout  with any sort of complicated track . which suggests that a near real time continuous update of position is possible 

9 minutes ago, Grovenor said:

The impession I have from the Railmagic site is that the locos should never be out of range, the idea being that magnets are cheap and you deploy enough of them to ensure that the entire layout is covered. Thus providing a continuous position reference.

I dont think so , as the manual mentions that you cant have too many close together , so it remains an issue whether complicated trackwork can be handled 

secondly the position is indicated by you the user. What happens is you place the magnets and then position the train within the magnetic filed and give the tracker the pattern ID  number , ie position A, it then memories the flux/field orientation patterns from magnets it can sense and applies your pattern ID to that pattern . Each time it detects that pattern it tells the RailMagic box  "hello 'Im at pattern ID # position"

The BEMF is simply used instead of commanded speed profiling ( TC & iTrain ) as as means of then estimating run distance from a known point . This is used to effect a slowdown and stop , but then TC does that to  

what's clear is there is no continuous position update process , That requires triangulation , each "spot" detection point is logged by you and a calibration is performed to acquire the calibration at that "spot "

1 hour ago, NIK said:

Hi,

 

But RailMagic does know how to work out the position more often as every time a magnet comes within range RailMagic can adjust the estimate of where the train is. I agree RailMagic's use of back EMF info fed back to the RailMagic control unit will fail if the loco is held manually in position and spins its wheels. However when allowed to go on its way it will update its position as soon as it comes into range of the next magnet. 

 

Regards

 

Nick

which is the same for every spot detection system linked back to a computer , ie TrainController etc , nothing new there 

We need to apply Railmagic logic , instead of scrolling the pages it would be better to display all pages and move the phone around the room in a augmented reality situation 

50 minutes ago, Andymsa said:

I didn’t make any reference to position data. The poster did not see why loconet would be involved when his system is downstream. Regardless of his system works there still needs to be a data sent back to the command station. This was in reference to a digitrax system .

My own view is that a Railmagic spot detector system that outputted  digital outputs that could be therefore feedback into iTrain , TrainController and jmri would actually be useful. 
 

I simply don’t buy the fact that this “ guy” in his bedroom is going to duplicate a detector system , the functionality of TrainController and produce a sound based DCC decoder to boot. 
 

That’s replicating the output of 3-4 established companies. 
 

cant see that happening 

2 hours ago, Andymsa said:

it is only down stream on the track feeds. But data still needs to go back to the command station via a data bus. For me that is loconet

The position data doesn’t go by loconet. His system includes a throttle capability whereby control is done using your existing command station  that needs a link to the command station 

4 minutes ago, njee20 said:

You do appear to be deliberately obtuse. All the systems use some logic and calculations to say “this train was at X position, travelling at Y speed, therefore it’s now here”. Whether that’s done by profiling the speed of a loco and defining the length of each block, or by using back EMF, or magic, it’s still the same. It’s deducing where a train is until it is told the next position.
 

Regular speed feedback is no more useful than knowing a loco is at speed step X and that means Y mm/second covered, if I held my finger in front of a loco either system would fail. Railmagic is not a solution in this respect. It is not providing real-time position info.   

True. However BEMF sensing has some advantages over simple speed profiling from commanded speed as it “ in theory” takes into account load changes etc. “. However in practice it can be very difficult to accurately characterise the relationship between actual motor speed and bemf 

Note the reason he’s doing his own decoder and has issues with BEMF in other decoders  is that to measure BEMF he needs a “ quiet “ period in the motor drive waveform to sense accurate bemf. He may be finding that difficult to achieve. 

8 minutes ago, NIK said:

Hi,

 

If the tracker is providing speed info back to the RailMagic control unit (why else would it be connected to the motor terminals) then when a magnet is not within range then it uses the speed info to work out where the loco has got to. Existing software does not do this as it gets no regular speed feedback.

 

I agree it doesn't cover rolling stock detection.

 

Regards

 

Nick

The net effect of whether you simply do speed profiling , ie the relationship between commanded speed and motor speed , or whether you use BEMF and equally a speed profile calibration to relate BEMF to speed over the ground is somewhat a moot point 

given fixed gearing both derive the same information ie an estimate of distance covered. Both are “ estimates” neither is actually doing direct measurements ( which a continuous positioning system could do) 

22 minutes ago, NIK said:

Hi,

 

Because of the way RailMagic works it may not be possible to interface it to existing software.

It seems to generate a stream of position and speed data which it uses internally to control the speed of the train.

 

Existing software uses layout mounted specified location sensors (a loco just passed here messages) and then rely on the repeatability of the DCC decoder and the loco pickups to stop a loco at a certain place.

 

Regards

 

Nick

I think all Railmagic does is spot detection , It does  not Re compute position as it moves based on triangulation , it merely report a spot position reached and used BEMF dead reckoning in between “ spot “ detection 

You can do exactly the same thing with lineside spot detectors and Railcom speed feedback. ( which is actually independent of BEMF and  hence much more accurate )  

Railmagic still needs loco speed profiling because you have to relate BEMF levels to actual forward movement. 
 

all in all it’s a spot detection system at heart. 

1 minute ago, Andymsa said:

want is one thing, actual reality is another. Your basing your thoughts on how railmagic works on speculation. 

Well it’s all speculation until it’s confirmed. But based on reading the manual it’s not capable of triangulation all its doing is “ remembering a flux or field orientation pattern at a known point “ when it sees that “ pattern “ again the tracker in the loco reports it’s at the known point via the DCC link which is detected by the Railmagic box 

10 hours ago, Grovenor said:

I don't see any relevance to loconet as the railmagic stuff is all downstream of the command station/booster.

Presumably to allow throttle control via the command station , he’s not proposing to override the command station DCC 

2 minutes ago, NIK said:

Hi,

 

I speculated that a tiny square black electronic device on the RailMagic tracker that was the same size as a 3 axis magnetic field detector I found in an online  electronic catalogue was the magnetic sensor for the tracker.

 

We know the tracker is connected to the motor connections of the DCC decoder.

RailMagic say info is sent back from the tracker to the RailMagic control unit.

The RailMagic control unit is interposed between the command station/booster and the track.

 

So it could be speculated that the system may be able to get pretty regular updates from each loco as to where it was when it was in range of a magnet and what speeds it has been doing.

 

If that is true then it is different from existing train automation systems that get info from a layout mounted sensor that a loco reached a waypoint and then rely on certain types of DCC decoder to repeatedly stop the loco with accuracy.

 

My club layout could do with a system that could display where locos are and what speeds they are doing as when operating from the fiddle yard at the back of the layout the backscene hides the train from view on the scenic section.

 

I'm not sure that RailMagic will offer such a feature.

 

Regards

 

Nick

 

 

 

Nick. Continuous position updating would be a game changer. But it looks like Railmagic doesn’t do this. It seems to build a pattern of the fields at a specific series of known points on the track. It then uses BEMF to essentially dead reckon from  that known point 

Given that’s seems to be the case. This is essentially just another spot detector system. It suffers from all the issues of spot detection ( ie block occupancy is hard to do , what about rolling stock in the section etc ) 

At present Railmagic is a closed shop system. Ie you need all his software which essentially is a replacement for TrainController or iTrain. Given it will take several years to rival the features of these packages , it might have been better to design a system that could have been interfaced to these types of control solutions. 
 

given most proper DCC layouts are wired with track droppers , adding spot or section detectors is a simple addition , so the claimed advantages of Railmagic in using magnets are not going to transpire in real situations , moreover the disadvantages of adding an additional circuit board in the loco are very real and present a significant difficulty. 

12 minutes ago, Andymsa said:

Just been looking at the manual again, currently the max current is 3amps although it does state 5 amp maybe. Also track voltage 14/20. These ratings will rule out many users. Also Märklin users must use Dcc commands, although not common here in Europe it is so those users are out if they don’t want to use dcc commands.

We run at 8A on the O gauge single booster 

…

33 minutes ago, Nigelcliffe said:

 

You're assuming it measures flux.   What follows is speculative, and could be entirely wrong...

 

Someone posted earlier/elsewhere an identification of a three-axis magnetic sensor (similar to those used in quite a lot of smartphones) in the loco-mounted detector device.   It may measure field orientation as it passes a magnet cluster, which is far easier than flux levels.    (The measured field orientation in each loco will be different due to differences in how the detector is installed, but that's OK).   

 

If the layout configuration is known (which it is, the user has to draw a track plan for the system), then I have a back-of-envelope scheme which can identify loco position with a few (around four) different magnetic field patterns.   Those can repeat around a layout because the track is known, the possible "next pattern" for a train whose current position is known is tightly restricted.   In practise, the magnetic field orientations will be subtly different each time, and the three-axis magnetic sensors are pretty sensitive to field orientation, so all fields being unique around a layout is the most likely outcome.   

 

 

 

The software drives trains and changes turnouts on the layout as part of driving trains.   If one owns one of the listed command stations, they all have graphical user interfaces showing track position.    If the RailMagic is changing turnouts (downstream) is has to communicate back up to the command station to inform it of new turnout positions, otherwise the track diagram provided by an ECoS/Z21 (etc.) will be wrong, and the user can't manually drive trains.    

 

LocoNet is one way to communicate that information back to the command station.   Yes, Digitrax own the rights to LocoNet, and provide licenses to other makers.   

 

On RailCom, which has been talked about, the preamble for a Digitrax command station is a "short" preamble, which only allows the basic short RailCom messages.   For Roco, ECoS and Digikeijs, the preamble is a "long" one, which allows the full long RailCom message.    (The other very common US system, NCE, is even more problematic for RailCom due to the preamble bits ).

 

 

 

 

As I said, all speculative.   

 

 

- Nigel

Surely field orientation would be modified by the presence of ferrous metals , other trains , etc. 
 

If it can measure multiple field orientations it should be capable of continuous position calculations and would not need BEMF dead reckoning 

9 hours ago, RFS said:

Best DCC practice for anything but a small layout is two wires to every piece of track, regardless of whether you are using automation or not. This is also something that Railmagic have not grasped with their claim of being able to return to just two wires to the track.

I think he doesn’t understand the hobby at all quite frankly 

I had a copy of the above somewhere and  icant find it , has anyone a drawings of a suitable roller gauge 

thanks dave 

Given the complexity of resolving different magnetic flux densities , the system must struggle to scale up to large layouts with many magnets as the patterns could be very difficult to resolve , then you add the effects of external magnets , other ferrous objects on the layout ( for example a TMD , which lots of locos sitting together , or an O gauge train of 6 metal carriages passing.  Hmmmm 
 

12 minutes ago, RFS said:

 

We're still very much in the dark as to exactly how it works. But we do know it also relies on Back-EMF data from the motor, hence why the tracker has to be connected to the motor terminals.  This is to give Railmagic an estimate of how far the loco has travelled, presumably between magnets, data that is then fed back to the Trainiac. Given that he has also revealed he has had problems with inaccurate data from Back-EMF, and therefore is going to design his own decoder with tracker built in, we have to wait and see how accurate this positioning is.

 

Traincontroller and iTrain tracking is extremely accurate using "dead reckoning" so I think Railmagic will have a challenge to match that. 

As I said it’s a spot detector followed by dead reckoning , this is exactly what TrainController , iTrain do. In these cases they can’t sense BEMF so they use a predetermined speed profile but the end result remains a dead reckoning system. 
 

using BEMF is fraught  with issues, ie gradients between magnets , friction slowdowns. Heavy versus light loaded trains , wheel slip 

It’s a complicated spot detection system that’s all 

i think on reflection its fairly easy to understand the basic principles given what’s written in Railmagics manual. 
 

the advantage of Railmagic is you can implement multiple spot detectors without baseboard wiring but this is balanced by having to retrofit all locos with an additional module and the imposition of limits on the DCC configuration 

I think I end up with the baseboard wiring !! 

By the way. The reason he has issues with multiple boosters is he must intercept the DCC signal between the track and the booster not only to inject commands ( using a reserved loco long  address ) he must also receive the communications from the loco mounted Railmagic “ tracker “. Hence of the loco shorts two boosters he suddenly has a loco sending pattern IDs to two listeners. 
 

I suspect this system doesn’t scale well at all. ( It’s unclear how it handle say a 4 track main line or a  complex station throat 

15 minutes ago, Andymsa said:

so in reality it has no advantages over current systems, hence the claims of millimetre precision stopping should be viewed very carefully. 
 

your comparison of RFID is quite correct, I hadn’t looked at it that way.

Any spot detection system can claim “ millimetre precision , after all the spot  detector is fixed. Once tripped further calculations rely on “ dead reckoning “ ie calibrated loco response to DCC speed  commands , which Railmagic  also needs. 
 

in one fell swoop he’s invented …..iTrain 

Only difference is track side spot detectors force the installation of wiring to each spot detector but the loco doesn’t require much of any modification

railmagic merely swops  that complexity of baseboard wiring for the issue of fitting another module in the loco and then modified the DCC signal to get the tag number ( in this case a magnetic pattern ID) back to its control station( which is why he currently needs a full train length of isolation between boosters ) 

Given the limit of 16 locos I suspect he’s modifying the DCc idle packets to return pattern ID info to his “ trainiac” ( this guy needs to get out more ! )  to many active locos would prevent him from getting enough idle times to transmit the ID info. 
 

Really he’s bending the DCC spec and that’s not good ( the same can be said of Zimos HULU protocol which modified the DCC preamble sequence ) 

other then curiosity value I don’t see any advantages and I see several disadvantages.