Britannia Builder Posted July 23, 2023 Share Posted July 23, 2023 A couple of weeks ago I had to reset the 8TXS decoder in my Bachmann 3MT Tank following a loss of DCC control, as reported previously on this forum.I then set it up again by laboriously entering all the modified CVs, including my complex speed curve, and re-ran auto calibration. Since then the loco has 'hunted' at medium speeds, ie the speed regularly oscillates above and below the average - not too badly, but enough to be noticeable. I hadn't noticed this previously.After a lot of head scratching I consulted the famous manual and saw on page 112 a warning (in red type!) that the auto calibration must be done with all the speed curve CVs set to default values. So I set CV29 bit 4 to use the default simple speed curve (without changing my complex speed curve) and re-ran the auto calibration. This seems to have cured the 'hunting' problem. CVs 145-147, set by the auto calibration, were 49/15/4 after the erroneous calibration, and 25/11/3 after the second one.It's a bit surprising that the speed curve should affect the auto calibration - I assumed that it just applied maximum voltage to the motor and monitored the back emf to see the acceleration - but perhaps it uses speed step 127 of the speed curve to decide what voltage to use? This would tie in with the acceleration being about half as much with my complex speed curve, which has a much lower top voltage.I can't really fault the manual, and I had read it from cover to cover at the outset, but it's easy to overlook these things when one becomes familiar with the procedures. The interaction between auto calibration and speed curves is not intuitively obvious.Just thought I'd point this out in case anyone else gets caught out by it!Regards, John Link to comment Share on other sites More sharing options...
WilliamDavid Posted July 24, 2023 Share Posted July 24, 2023 Is it worth doing Auto calibration on installation? Link to comment Share on other sites More sharing options...
SteveM6 Posted July 24, 2023 Share Posted July 24, 2023 Probably not if you are fitting the decoders to Hornby locos as they should be matched already.However if you are fitting them to another manufacturer’s products or if there is any sign of jerky running then it would make sense to do so. Link to comment Share on other sites More sharing options...
Britannia Builder Posted July 24, 2023 Author Share Posted July 24, 2023 Yes, I've always done it when installing. It's very easy and it seems to help. Despite the warnings it doesn't really need a very long straight - 3-4 feet seems ample and if it goes a bit round the curve as it decelerates I don't think it really matters. I just got caught out by doing things in the wrong order after having to reset the decoder. I've achieved excellent motor control on my 4 TXS locos without having to do the stage 2 (PA) or stage 3 (PID) adjustments described in the manual.Incidentally I did try the PID mode out of interest - I set CV149 to 1 and tried with the default values, and nothing seemed to change - I then tinkered with the P value but again it made no difference. Then when I ran the loco the next day it behaved dreadfully - it looks as though you need to power cycle the decoder after setting CV149 to 1 in order for it to notice the change! I reverted to CV149=2 and power cycled and all was well.Regards, John Link to comment Share on other sites More sharing options...
Rallymatt Posted July 25, 2023 Share Posted July 25, 2023 On the motors fitted in the TT:120 Hornby locos and other manufacturers I have found the auto calibration well worth doing, particularly as it’s so easy with the HM DCC app. I have just this weekend further fine tuned running by setting CV 144 to value 1. The power of HM DCC means you can try things that were previously shrouded in mystery and if they don’t improve running, instantly re-instate the original parameters. Link to comment Share on other sites More sharing options...
WilliamDavid Posted July 26, 2023 Share Posted July 26, 2023 Had a go with auto calibration. Sort of no difference with five locos, but weird results with my Hornby Lord Rodney. Very erratic.I reset them all back to factory settings.All good enough as they came. Link to comment Share on other sites More sharing options...
Rallymatt Posted July 26, 2023 Share Posted July 26, 2023 WD, just out of curiosity, did you try setting CV144 to 1 after the auto calibration process? That’s stage 2 of setting motor control, stage 3 is getting into PID settings and I’m happy leaving that alone 🤣 Link to comment Share on other sites More sharing options...
WilliamDavid Posted July 27, 2023 Share Posted July 27, 2023 I went through the whole procedure with this loco. It seemed to run rather slow and undoing.I see CV144 to 1 and it ran more smoothly but still slow. Reset CV8 and it ran just fine.I’ll leave things as supplied. Link to comment Share on other sites More sharing options...
Rallymatt Posted July 27, 2023 Share Posted July 27, 2023 Thanks, it was interesting to hear how it went. It’s a great feature of HM DCC that it’s so easy to make changes and reset everything if it’s not ideal. 👍 Link to comment Share on other sites More sharing options...
WilliamDavid Posted July 27, 2023 Share Posted July 27, 2023 I agree.I am a tinkerer, and can do so without fear of destroying £60 of kit.I love these things. Link to comment Share on other sites More sharing options...
Too Tall Posted August 5, 2023 Share Posted August 5, 2023 Ok excuse me being a newbie to this, but having just got my first HM7000 decoder I was really chuffed (sic).I set accel and decel to my preference and best guess as to how I though might be realistic (I ended up at 75 accel and 36 decel ?).The one thing I thought was off, was rolling too fast to soon from a stop, and too slow to go from mid to high and to fast from high to top speed.So I was going to try the CV settings 96RAF posted for 3 cyl in the Complex speed curve thread.But what I would also like to know,:Is it fine to run auto calibration with my accel decel set as they are ? What would be a suitable top speed setting (CV5 I believe) for the Pacific locos to be realistic in TT120 ?What does the CV144 to 1Rallymatt mentions actually do ? Link to comment Share on other sites More sharing options...
96RAF Posted August 5, 2023 Share Posted August 5, 2023 Have a read of Appendix 6 of the famous manual to get an overall understanding of how speed curves and motor PID characteristics work together.The PID affects the way the motor reacts to the throttle by way of smoothness of control.The speed curve simply tells the motor to go this fast at that speed step. The speed curve settings thus affect how the throttle rate is seen by the motor, either linear or curved with a bias to lower or higher speed control.The default Accel/Decell for TXS is value 15 to allow the start sounds to play through before the loco moves. If you alter these values the loco will move before the sounds have finished (low values) or the loco will not start on cue and the sounds may play twice. Link to comment Share on other sites More sharing options...
Too Tall Posted August 5, 2023 Share Posted August 5, 2023 Assuming a "general decoder reset" means I'll have to reload the sound files ? neutral_face Link to comment Share on other sites More sharing options...
Brew Man Posted August 5, 2023 Share Posted August 5, 2023 You shouldn't need to re-install the sound file from scratch, I think you just need to import the running profile. It doesn't take as long.EDIT: Yes, if you've reset the decoder, you might have to start from scratch. But do you need to reset? Try just importing the running profile first. Link to comment Share on other sites More sharing options...
Too Tall Posted August 5, 2023 Share Posted August 5, 2023 It (the manual) advises:"before any attempts of Auto-Calibration are carried out, it is important that All CVs involving Speed Curves are set to default. Also, ensure that CV10 (BEMF Cut off point) is set to = 127 (default.) Performing a general decoder reset is the easiest method of ensuring that you always start with known basis before carrying out any tuning."Assuming I have loaded a hornby profile, its not on defaults ?Its a PITA if I have to reload the sound files for 45 or so minutes !Edit .... well it seems irrelevant as the software wont let me set 0 for calibration anyway face_with_rolling_eyes Link to comment Share on other sites More sharing options...
96RAF Posted August 5, 2023 Share Posted August 5, 2023 Auto cal is a DCC operation at present.After a reset you can check which sound profile is loaded. In manage device. Link to comment Share on other sites More sharing options...
Too Tall Posted August 5, 2023 Share Posted August 5, 2023 Ah that explains that ! Thanks 96RAF.Either i missed it or is there a way to save a profile you have created with custom CVs ?If it wasn't me not looking hard enough, then it certainly sounds like a good call for a future software update.Pity about the sound timings not matching if you alter the accel rates, as I like to dial it to the desired cruising speed and have the loco gently accelerate to it. Link to comment Share on other sites More sharing options...
Too Tall Posted August 6, 2023 Share Posted August 6, 2023 so as I appear incapable of finding the auto calibration in the Elite manual, and it is not yet enabled on the HM7000, could someone explain the procedure please ? blush Link to comment Share on other sites More sharing options...
Fishmanoz Posted August 6, 2023 Share Posted August 6, 2023 Not in the Elite manual as it is a decoder function. See procedure on page 113 of the HM7000 manual for running with your Elite (use program/track outputs as appropriate). Link to comment Share on other sites More sharing options...
Britannia Builder Posted August 6, 2023 Author Share Posted August 6, 2023 I'm a bit puzzled by the assertion that auto calibration only works under DCC - I used the app to set CV149 to zero. It may well be that the loco was under DCC rather than bluetooth control at that time, but I didn't have to use the old fashioned programming track method to change the CV.I also disagree with the manual's assertion that a general decoder reset is the easiest method of preparing for tuning - as I explained in the first post of this thread, using the default simple speed curve seems sufficient, and reloading the profile seems to me to be overkill.Regards, John Link to comment Share on other sites More sharing options...
Too Tall Posted August 6, 2023 Share Posted August 6, 2023 Are you using an apple product ?As CV 149 is definitely greyed out on my android tablet. Link to comment Share on other sites More sharing options...
Too Tall Posted August 6, 2023 Share Posted August 6, 2023 To check my thick noggin has this right, using the elite to do it (after setting loco to DCC control).Place loco on programing track, select cv29 and enter 4 then cv149 and enter 0.Once the red light has finished, place loco on main track, press function and then the number 0, loco should move for a short time and then its done ? Link to comment Share on other sites More sharing options...
96RAF Posted August 6, 2023 Share Posted August 6, 2023 If you modify any of the imported loco running prifile you can export that saved as whatever name you want to give it, then reimport the custom profile to the same or another loco. E.g.if you have a few Brits, some ringfield powered and some can motor powered which require different running profiles then save one as Brit1 and the other as Brit2 and you can import those to the rest of the split fleet. Link to comment Share on other sites More sharing options...
96RAF Posted August 6, 2023 Share Posted August 6, 2023 To check my thick noggin has this right, using the elite to do it (after setting loco to DCC control).Place loco on programing track, select cv29 and enter 4 then cv149 and enter 0.Once the red light has finished, place loco on main track, press function and then the number 0, loco should move for a short time and then its done ? Why are you fiddling with CV29. Link to comment Share on other sites More sharing options...
Britannia Builder Posted August 6, 2023 Author Share Posted August 6, 2023 Are you using an apple product ?As CV 149 is definitely greyed out on my android tablet. I'm using an iPad, but perhaps CV149 is greyed out if you are under bluetooth control at the time you try to change it? I haven't tried that.Regards, John Link to comment Share on other sites More sharing options...
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