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Forums > CSDb Entries > Release id #160665 : Stepper Test 1.0
2017-11-30 14:02
ChristopherJam

Registered: Aug 2004
Posts: 1359
Release id #160665 : Stepper Test 1.0

Copying the production notes below, but I'd really like to see some results from other people's drives for this one.
 
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2017-12-01 10:20
Tom-Cat

Registered: Apr 2003
Posts: 20
Here is my 1541-II that I currently have attached to my c64c:



Looks ok ? :)
2017-12-01 10:22
Oswald

Registered: Apr 2002
Posts: 5007
you win the graph niceness compo so far :)
2017-12-01 10:41
icon

Registered: Apr 2002
Posts: 89
Here is two of my drives (more to come):

1541 (grey and cold)


1570 (white and cold)
2017-12-01 14:56
chatGPZ

Registered: Dec 2001
Posts: 11088
Quote:
that drive is *fast*! Did you install a turbo?? Code would have to have a bit of a redesign to zoom any more tightly on that top edge.

random old drive, i only ever cleaned the head and rails and made sure its 300rpm :) (it would be nice of your program had a few maintenance features... like rpm check, motor on/off switch, step to track 1/18/35)
2017-12-01 16:41
Impetigo

Registered: Jun 2004
Posts: 30
My Oceanic:
Stock JiffyDos kernel, high current power supply.
Doesn't work properly with the original power supply.

2017-12-01 18:12
Dr.Science

Registered: Oct 2011
Posts: 39
1541-II (cold)
2017-12-03 08:54
ChristopherJam

Registered: Aug 2004
Posts: 1359
Thanks everyone, those are all really useful.

Spending too long on the half track is looking pretty costly on a lot of drives, especially if you catch that spike somewhere around 20-24 bycles. Entertaining given that 25 bycles is the default stepping time before acceleration kicks in..

I suspect what's happening there is the head is oscillating a bit, and that far in it's swung almost back to its starting point. I've tried running a simple physics sim with acceleration proportional to sin((phase-desiredphase)), and friction proportional to velocity. My friction model clearly needs work, as it keeps ringing for far too long, but even with the model as it stands I can already see shapes that loosely approximate some of the readings.



Some sets of parameters indeed result in a spike if the head has almost returned to the starting track at the end of T1, supporting my hypothesis above:


        def iter(x0,x1):
            a=np.sin((target-x1)*np.pi)
            v0=(x1-x0)/dt
            dv=v0*dt/Td
            v0=v0+a*dt*Ta**-2
            v0=v0-dv
            return x1+v0*dt

(iter calculates the new head position as a function of the previous two, assuming a constant timestep of dt. Head position in tracks.)
2017-12-07 16:23
ChristopherJam

Registered: Aug 2004
Posts: 1359
Â…and some more measurements, these from j0x (thanks again!)

Two from an old 1541 push-down mech drive:




and two from an (almost as) old 1541-II:


2017-12-29 19:15
soci

Registered: Sep 2003
Posts: 472
A bit late, but anyway.

1541-II with refurbished mechanic:


1571:


Another 1571:


Old 1541:


1571CR:


Unfortunately I couldn't do my oceanic this time as it's not here. That'll be interesting as it has an unusual stepper motor and mechanic.
2018-01-01 23:55
ChristopherJam

Registered: Aug 2004
Posts: 1359
Thanks Soci.

Those 1571s are particularly slow; well worth knowing about.
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