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Many (All?) PS3 MTH steam engines now lock up and skid to a stop and do not gradually coast in conventional mode. All is well in DCS. 

I've got a brand new GS4 Daylight, an engine I've wanted for years, that has this issue. Otherwise it runs great. MTH has said the coasting issue is a software issue, not a hardware issue. They are aware of it but don't really intend to fix it. Personally, I prefer conventional operation (use it at home) and more "low tech" trains. 

Has anyone removed the PS3 boards and put in, for example Dallee boards? Would it coast?

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I'm going to go into an area where I don't have all the facts and am only working off of theory and such.  I don't know enough about these engines to know if anything that follows is actually true in this particular case.  

There are two things I can think of that contribute to an engine coming to a sudden stop when cycling to neutral.  The first is the mechanical drivetrain.  it may be that the gear box is designed in such a way that if the motor is unpowered the wheels simply can not turn.  If this is the case, one would need an e unit that gradually reduces motor power in order to get any sort of coasting effect.  The second is that the e-unit in place may be effectively connecting both of the motor's connections together, which would cause the motor to act like a brake on the drive train.  If this is the case, using an e-unit that floats the motor when it is unpowered may allow it to coast...some.  

I'm unfamiliar with the Dallee unit, so I don't know if it would help with either of these problems.  I do know that if one were so inclined they could fairly inexpensively construct their own e-unit that could counter either problem.  One might even be able to do something inline with the PS3 electronics that would allow all of the engine's sounds and features to remain intact while allowing the engine to coast to a stop.  

All that said, I'm curious why it wouldn't be worth the time to code the boards properly in the first place.  It seems to me there are plenty of people that run conventional, and  a strong contingent of folks that are only interested in conventional operation and have no desire to ever run any form of command.  If I bought an engine advertised to be fully functional in conventional, I'd like it to perform well in that environment.  I've always used the direction buttons to stop, and expect many others do as well, sort of a "feature" of conventional running in my opinion.  

JGL

SJC posted:
... MTH has said the coasting issue is a software issue, not a hardware issue. They are aware of it but don't really intend to fix it.
 

I know you've been all over this issue for over a year now.  Earlier this year you commented in another thread that MTH is/was working on a PS3 software update for this.  Do you have new information that this is no longer the case?

stan2004 posted:
SJC posted:
... MTH has said the coasting issue is a software issue, not a hardware issue. They are aware of it but don't really intend to fix it.
 

I know you've been all over this issue for over a year now.  Earlier this year you commented in another thread that MTH is/was working on a PS3 software update for this.  Do you have new information that this is no longer the case?

I contacted MTH's Andy E. about this in March of this year. Per his email back, R&D would look into it again to see if a software update was possible. I did just follow up last night about it, hopefully I'll get something in the next few days back. He did note that a previous attempt to fix this, several years ago failed. It failed because 1) Little consumer feedback 2) Lack of positive results in the fix the tried. 3) Declining numbers of conventional control operators. 

 

gunrunnerjohn posted:

See my post about the issue.  I'm wondering if some diodes and a directional relay would fix this.  I suspect it's because of dynamic braking when the power is removed and the drivers provide a current path from the motor leads and stop the motor too quickly.

Link?  I don't know about his specific collection of PS3 engines but there's not much room to add a relay.

If this is the dynamic braking issue as JGL and GRJ surmise, it seems to me it would also show up in command mode when E-stop is pressed as track power is instantly removed from the track.  Point being while E-Stop is not a "normal" operating mode the software fix would benefit more than just the conventional guys.

stan2004 posted:
gunrunnerjohn posted:

See my post about the issue.  I'm wondering if some diodes and a directional relay would fix this.  I suspect it's because of dynamic braking when the power is removed and the drivers provide a current path from the motor leads and stop the motor too quickly.

Link?  I don't know about his specific collection of PS3 engines but there's not much room to add a relay.

If this is the dynamic braking issue as JGL and GRJ surmise, it seems to me it would also show up in command mode when E-stop is pressed as track power is instantly removed from the track.  Point being while E-Stop is not a "normal" operating mode the software fix would benefit more than just the conventional guys.

Link is HERE.

This GS4 Daylight is the only PS3 steam engine I have presently that has this issue. I know of at least two others I have had that have the 'quick stop" issue. One is the MTH Imperial Mikado and the Other is the MTH Imperial 0-8-0 switcher, both PS3 products.  FWIW, my only other PS3 steamer, an Imperial Railking 0-6-0 (from 2013) DOES coast in conventional and operates beautifully. It doesn't coast as far and long like some other PS2 engines but it doesn't skid to a stop.

I apologize for not address JohnGaltLine's post sooner. Without power, the drive wheels can't be turned due to gearing. This is common with all MTH locos. I use the direction  button all the time, especially when switching. Granted I won't be switching with a large 4-8-4 passenger engine but still, even throttling down a bit quick will cause it to lock up and skid. Extreme caution is required. My biggest concern with this issue is the gears getting chewed up after this happening one too many times, even with extreme care in preventing it. This is especially true on the club layout with several people operating on the same track at once. One E-stop press or short is all it takes.

A heavier flywheel seems in order; I guess that they have been using a software solution to fix a mechanically-correctible problem. If so, not a good idea. So 21st-Century, it seems, on the surface. But I don't know.

My WBB 027 Alco FA-2's, which I upgraded to ERR Cruise Commander/RS, have light flywheels and to not coast (stop gracefully) as well as I would like, but it's not bothersome - I know how to drive them.

Flywheels - not software. That's the ticket. 

Hot Water posted:

Why does it have to "coast" anyway?

As SJC says, if you remove track power (by pressing the DIRECTION button) the engine locks up coming to a violent halt and potentially de-railing cars.  It has been pointed out that the same engine, same motor, same flywheel, but different electronics/software (PS2 vs. PS3) behaves differently.  Hence it's not that MTH is replacing or trying to replace the flywheel with software.  Instead it seems the PS3 electronics/software is behaving in a manner which demotes the coasting potential of the flywheel.  As discussed the consensus is dynamic braking (something which the software can apparently control) is stealing this coasting energy from the spinning flywheel for whatever reason.  In the case of a hybrid-electric vehicle, dynamic braking is used to charge the battery.  I wouldn't expect to see any published analysis of if/how/why MTH changed the flywheel dynamics going from PS2 to PS3.  For that reason I don't think there would be substantial gain to simply increasing the size of the flywheel.

In addition to violently derailing the train behind it, this issue also SHREDS the traction tires if you are not careful. Not to mention, I'm sure it does a number to the motor, steam driving wheels/valve gear and internal gearing. I want and expect to have these trains running for years to come.

Andy at MTH got back to me. He said R&D was going to look into it and he would follow up and get back to me if there was any news. R&D tells Andy that if there is a simple software fix, they will pursue it.

So, at this point am I correct in saying that the drivetrain in question is not the most awesome to allow the engine to coast to a stop, but that the same exact drive drain (gears, motors, flywheels, etc) DOES coast to a satisfactory amount on engines with the PS2 electronics.  

Under that assumption, does anyone have some photos of the PS2 and PS3 boards in use?  I know that in at least one of these relays are used to switch the power control to the motor(s) and am curious if the other uses semiconductors instead to form the H-Bridge. (Triacs, FETs, Transistors, etc.) The semiconductor method naturally floats the motor where it would not cause substantial breaking, where as a relay H-Bridge would when wired in typical fashion.  

Before hypothesizing further I'd like to see the boards in question just to get an idea of the components in use.  

JGL

See disclaimer in my previous post if needed.  

SJC posted:
...
He did note that a previous attempt to fix this, several years ago failed. It failed because 1) Little consumer feedback 2) Lack of positive results in the fix the tried. 3) Declining numbers of conventional control operators. 

 

If cars derail, traction tires shred, gears slam together, etc. when you press E-stop or when a breaker trips from a track short...then I'd this is an issue for ALL users, not just the conventional guys.

I'm surprised there hasn't been more "consumer feedback" from command operators. Or if lack of feedback means the command operators don't care, perhaps it would be easier for MTH to alter the coasting software only when in conventional mode. 

At minimum it seems your cause can only be helped if other conventional control operators would send a note to MTH about this issue. 

FWIW, I notice that with DCS (had to find my long lost DCS set), the same "quick stop" issue is present with the E-Stop command. Double tap of the brake button and direction button both brought slow, coasting stops. Deceleration was set at 2, I cranked it up to 25 (limit) and noted the engine would now "quick stop" like it does in conventional. Turning it down to 1 brought nice, coasting stops. Back in conventional, no changes whatsoever. 

Well, now we're shooting in the dark and speculating.  From what I've read this occurs in PS3 STEAM engines.  Since the flywheels are the same in PS2 and PS3, and PS2 coasts just fine, the question is what's different?  AFAIK, all PS3 steamers have a processor in the engine (in addition to the one in the tender).  PS2 only has a processor in the tender.  Of course the flywheel in a steamer is in the engine (and I haven't read reports of this happening in a diesel).  So it could be about the "new" software in the engine processor and how it interacts/uses the energy in the flywheel that's the design issue.  Apparently MTH understands the issue (and we don't) so we're just playing 3-blind-mice scurrying around for cheese...

I suggest there's little to be gained in speculating why/how MTH designed the coasting software as they did.  I'm more curious about if anyone other than SJC has even given them feedback.  To that end, that's why I suggest if this is a concern to anyone to send a note to MTH.  From what I can tell MTH has not said "no"... and the squeaky wheel does get the grease.

 

 

stan2004 posted:

Well, now we're shooting in the dark and speculating.  From what I've read this occurs in PS3 STEAM engines.  Since the flywheels are the same in PS2 and PS3, and PS2 coasts just fine, the question is what's different?  AFAIK, all PS3 steamers have a processor in the engine (in addition to the one in the tender).  PS2 only has a processor in the tender.  Of course the flywheel in a steamer is in the engine (and I haven't read reports of this happening in a diesel).  So it could be about the "new" software in the engine processor and how it interacts/uses the energy in the flywheel that's the design issue.  Apparently MTH understands the issue (and we don't) so we're just playing 3-blind-mice scurrying around for cheese...

I suggest there's little to be gained in speculating why/how MTH designed the coasting software as they did.  I'm more curious about if anyone other than SJC has even given them feedback.  To that end, that's why I suggest if this is a concern to anyone to send a note to MTH.  From what I can tell MTH has not said "no"... and the squeaky wheel does get the grease.

 

 

FWIW, Barry Broskowitz reported, after testing, that his Imperial Mikado also had the "quick stop" problem and reported it to MTH so I'm not the first one to tell them. 

I should also reaffirm that I have another PS3 steamer, 30-1570-1, that DOES coast in conventional. This is, apparently, a recent PS3 steam issue. 

Last edited by SJC
SJC posted:

I should also reaffirm that I have another PS3 steamer, 30-1570-1, that DOES coast in conventional. This is, apparently, a recent PS3 steam issue. 

I clearly missed that comment.  So there is hope.  From day 1 I've thought that one of the key benefits of PS3 is ability to update not just the soundset (as with PS2) but the actual engine operational software to give it new features (or fix bugs).  So maybe the task at hand is how they manage the deployment of the "new" conventional coasting software and package it for the end-user.  I'd say there's light at the end of the tunnel.

Dave Zucal posted:

Bottom line, if you have a disaster about to unfold, wouldn't  you want your E-STOP button  to stop your train on a dime ????

I'll second this.  For the life of me, I can not understand the practice of simply pushing the "direction" button to change directions WHILE THE MODEL IS STILL MOVING! If an emergency is truly involved, then OK, but then wouldn't one push the "E-STOP" button?  Whether command or conventional, wouldn't one want to slow down, making a nice "realistic" stop, then push the direction button, and then back up?

On why one would want the wheels not to lock up when power is removed, aside from being extremely convenient in operation, I would think the main thing would be that if the purpose of an e-stop button is to prevent accidents, it would be pretty useless to have one that will cause derailments, and possible damage to the engine.  Whatever other reasons the ability to press a direction button and have the engine roll smoothly to a stop has been a "feature" of conventional running all the way back.  

On speculating about the hardware and software in use, until someone posts any information, even just photos of the boards that can show what is used to control the motors, there is little more that can be done.  I can guess as to hardware and/or software solutions that MTH could use, and can guess as to how the problem occurred from using standard design practices.  I can also guess about how an end user could solve the problem, but without knowing what the output stage of the ps3 electronics looks like, all I can do is guess.  

JGL

Edit: Also, as far as powering motors it wouldn't do much good, but for running the electronics, I'm under the impression that all PS2 and PS3 engines have a battery, so the electronics should have no problem continuing to run when power is cycled. 

Last edited by JohnGaltLine

MTH has always used relays to switch polarity and FET to control motor current, but continue to speculate. It is fun to do analysis without facts.

What is interesting and is a change on PS-3 O boards is there is a Brake motor FET.  I was told it is to reduce heat on the board.  Whether this FET shorts the motor current and prevents coast on loss of power is not full know.  I have removed these on diesel boards when they short and still have had the board function.  It is not designed as a brake, but does function similar to the smoke fan set up.  In that it can short PV to PCB ground at the motor terminals when commanded too.  I think I test the engine conventional with this FET removed and it still stopped abruptly, but I would have to go back and retest.

Could be software is flipping the PV via the relay and that is causing the braking.  So may be a combination of how it is built also.  G

GGG posted:

MTH has always used relays to switch polarity and FET to control motor current, but continue to speculate. It is fun to do analysis without facts.

 

Probably why I've asked twice now in just this thread for information on the output stage of the MTH boards.  Perhaps since you have so much experience with these boards you could (third time) post a photo or two of one of them. Perhaps share the knowledge and we won't have to speculate.  

JGL

GGG posted:

MTH has always used relays to switch polarity and FET to control motor current, but continue to speculate. It is fun to do analysis without facts .

What is interesting and is a change on PS-3 O boards is there is a Brake motor FETI was told it is to reduce heat on the board

...

Did whoever told you it was to "reduce heat" actually call it a "Brake motor FET"?  Or is that your term because it is wired into the motor drive circuit similar to the smoke fan configuration?

In pulse modulated circuits with inductive load such as a motor drive (but most commonly in switch-mode power supplies) it is now standard practice to use "synchronous rectification" to improve efficiency and hence reduce heat.  So the familiar re-circulation diode associated with driving relay coils, motor windings, or power supply coils is now replaced-by or augmented-with a FET.   A FET is a far more efficient switch than a diode with negligible voltage drop as compared to the tenths of Volts in a diode.  Thus, the voltage x current switching losses attributed to the diode become much smaller.  The trick is to turn the FET "on" at exactly the same time the original diode turns on - hence the term synchronous rectification. 

If the circuit still worked (no melt down or over-voltage blowouts) with this new FET removed, then the original diode may still be there and the FET is augmenting (in parallel with) the rectification.  You would have seen the benefit (reduced power loss) at higher power levels.

There's nothing magical about synchronous rectification.  But you do need circuitry to manage when to turn on the switch which, as with any technique, can get tricky at higher frequencies (kHz, MHz) as found modern power converter designs.  At slow frequencies (like 60 Hz) you could use an electro-mechanical relay to close/open when you want conduct/block current.

JohnGaltLine posted:
GGG posted:

MTH has always used relays to switch polarity and FET to control motor current, but continue to speculate. It is fun to do analysis without facts.

 

Probably why I've asked twice now in just this thread for information on the output stage of the MTH boards.  Perhaps since you have so much experience with these boards you could (third time) post a photo or two of one of them. Perhaps share the knowledge and we won't have to speculate.  

JGL

JGL, No time to post picture, but YOU could search the forum or internet and find them yourself.  There out there.

Stan my term not MTHs.  I did talk to Service about this post and it is a hardware issue that could be resolved via a revision to the board.  Not planned at this point.  The 3V used a diode to dissipate the energy of the motor when power cut off and hence the coast.  The PS-3 design is different and unfortunately the motor gets shunted to dissipate the energy and that causes the abrupt stop of the motor.  Does look like a diode is in there too. 

MTH is aware but not going to redesign the board at this point.  G

Last edited by GGG
Hot Water posted:
Dave Zucal posted:

Bottom line, if you have a disaster about to unfold, wouldn't  you want your E-STOP button  to stop your train on a dime ????

I'll second this.  For the life of me, I can not understand the practice of simply pushing the "direction" button to change directions WHILE THE MODEL IS STILL MOVING! If an emergency is truly involved, then OK, but then wouldn't one push the "E-STOP" button?  Whether command or conventional, wouldn't one want to slow down, making a nice "realistic" stop, then push the direction button, and then back up?

Yeah sure!

... but then the same three or four people can't bash MTH for stuff they discover (or hear of)!

GGG posted:
JohnGaltLine posted:
GGG posted:

MTH has always used relays to switch polarity and FET to control motor current, but continue to speculate. It is fun to do analysis without facts.

 

Probably why I've asked twice now in just this thread for information on the output stage of the MTH boards.  Perhaps since you have so much experience with these boards you could (third time) post a photo or two of one of them. Perhaps share the knowledge and we won't have to speculate.  

JGL

JGL, No time to post picture, but YOU could search the forum or internet and find them yourself.  There out there.

Stan my term not MTHs.  I did talk to Service about this post and it is a hardware issue that could be resolved via a revision to the board.  Not planned at this point.  The 3V used a diode to dissipate the energy of the motor when power cut off and hence the coast.  The PS-3 design is different and unfortunately the motor gets shunted to dissipate the energy and that causes the abrupt stop of the motor.  Does look like a diode is in there too. 

MTH is aware but not going to redesign the board at this point.  G

G...

Interesting post and info you have. The PS3 design is different than PS2 and as a result, this problem (no coasting) exists. There must have been a very recent change as my 2013 PS3 steamer DOES coast in conventional and has no issues. Same goes for diesels and twin motored steam. Perhaps it is just an issue with recent single motored locos.

Thanks for the info, I guess all I can do is hope there is a change, at some time.

Well, now I'm confused.  If I combine what SJC and GGG are saying, this is what I'm hearing:

The problem is fundamentally in the PS3 hardware design.  MTH is not planning to change the hardware at this time.  However, MTH is looking to see if there's software fix that can overcome the underlying hardware 'flaw'.  Do I have this correct?

Previously I was interpreting the fundamental problem as being in the PS3 software design. 

In other words, less promising if they are looking to a software change to fix a hardware problem...more promising if they are looking to a software change to fix a software problem.

Last edited by stan2004

Our electronic  Speed controllers in our RC flying stuff cab be set to  allow free spinning of the prop or a brake stop with throttle "off" .  The prop brake comes in handy when trying to land a glider  else the thing wants to fly for ever.   This is a software set up.(gliders are about the only plane where  I use it)

  MTH....Hardware or  software issue.  I don't know but I'd say your stuck with it  unless one of the tech guys can fix  you up.  

 

SJC posted:
GGG posted:
JohnGaltLine posted:
GGG posted:

MTH has always used relays to switch polarity and FET to control motor current, but continue to speculate. It is fun to do analysis without facts.

 

Probably why I've asked twice now in just this thread for information on the output stage of the MTH boards.  Perhaps since you have so much experience with these boards you could (third time) post a photo or two of one of them. Perhaps share the knowledge and we won't have to speculate.  

JGL

JGL, No time to post picture, but YOU could search the forum or internet and find them yourself.  There out there.

Stan my term not MTHs.  I did talk to Service about this post and it is a hardware issue that could be resolved via a revision to the board.  Not planned at this point.  The 3V used a diode to dissipate the energy of the motor when power cut off and hence the coast.  The PS-3 design is different and unfortunately the motor gets shunted to dissipate the energy and that causes the abrupt stop of the motor.  Does look like a diode is in there too. 

MTH is aware but not going to redesign the board at this point.  G

G...

Interesting post and info you have. The PS3 design is different than PS2 and as a result, this problem (no coasting) exists. There must have been a very recent change as my 2013 PS3 steamer DOES coast in conventional and has no issues. Same goes for diesels and twin motored steam. Perhaps it is just an issue with recent single motored locos.

Thanks for the info, I guess all I can do is hope there is a change, at some time.

What is the model steam that coast?  Same for diesel?  I would find it interesting you have a diesel that coast since those boards are the same.  In steam there is the FET verses relay boiler board.  It may be possible that a FET board coast but a relay board doesn't. (Relay steam is identical to Diesel as far as Motor control).

I just tested a PS-32 board I was loading a sound file into with DCS.  This is identical to a PS-3 diesel board.  I turned off power while the motor was spinning on my test set at 25 smph.  It stopped almost immediately.   G

Hot Water posted:
Gregg posted:

Hot Water . try your RS-3 to switch, scroll up the speed as fast as you can. hit the dir button for a quick reverse and scroll the speed up again  really fast  along  with  the rev up.... It's  really very realistic.

I don't have an "RS-3" whatever that is.

Ohio Central HW   Here's an RS-3  .It's Not EMD   and I don't know if it still in service.(ditch lights and all)

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