Newbie: Motorfader doesn't move to correct positio

[dominik]

Hello!

Unfortunately I don't understand much of what I am soldering, so I need your help to solve the following problem:

I realised the core module and different variations of DIN/DOUT-modules, all worked pretty fine.

Only recently I bought some ALPS faders and built the MF module. After adjusting the Vmm voltage to approximately 8 V (recommended by Thorsten) I tested one motorfader with the example driver given on the download page (I use the most recent MIOS version).

Unfortunately the fader does not move to the correct position but stops before (approximately 10 values before the destination).

Is this a question of calibration that can be handled by finding the appropriate values using the calibration tool? I also tried different voltage levels for Vmm - without success.

If this behaviour is a result of soldering errors: Where should I start to look for them?

Thanks for any advice,

Dominik

[TK.]

Hi Dominik,

since MIOS V1.4 the recommented calibration value for ALPS faders is 0x0e, so if you change this in the example application, it should work better. Or just try the MIDIbox MF firmware instead, where this is the default value.

If this doesn't help, perhaps your PSU isn't strong enough. Do you measure the 8V v_mm also during the fader is moved? Or does the voltage drop to a lower voltage level under load?

Best Regards, Thorsten.

[dominik]

Thanks a lot for the quick answer.

I changed the calibration constants in the example motorfader driver to 0x0e and noticed the same problems  :( with no voltage drops during fader movements.

As you recommended I then tried the MIDIbox MF firmware. After reducing the DEFAULT_NUMBER_FADERS constant to 1 it seems to work  :)

It seems as if the motor moves the fader very quickly in a first phase and approaches the final value with a slower speed afterwards (this last approaching seems to be missing in the motorfader example driver).

After a few tries some misplacements occured again and I increased the power (now to approximately 10 V). This workes quite well now, only sometimes when the lowest position is reached (value 0) the fader does not react anymore and has to be moved by hand before it is controlled by MIOS again. Any explanations for this?

One thing I forgot to mention (although I do not think it has an influence on this): I only mounted 7 ICs (lost the last one somehow). As far as I can read the connection diagram this should not disturb control of the other motorfaders, right?

Thanks again,

best regards,

Dominik

[dominik]

Just one more thing to add which shows (reproducable!) some problems with 0-values:

The value sequence 127, 0, 1, 0 does not lead to a move for the last change (1->0). The fader stays in the same position, you can switch between 0 and 1 as many times as you want, nothing changes!

Furthermore I noticed that after some 0-1-switching even value changes to 127 were ignored.

So far,

best regards again,

Dominik

[Steven_C]

I don't worry about fader not moving for a value of 1 out of 128 resolution...

[TK.]

Hi Dominik,

thats no bug, but a feature ;-)

from the MIOS source:

        ;; --- special case: if target and current position <= 0x07, stop motor
        ;; (workaround for ALPS faders which never reach the 0x00 value)

(0x07 in 10-bit resolution)

But you also wrote:

> even value changes to 127 were ignored.

could you please send me a .mid file which reproduces this problem?

Best Regards, Thorsten.

[dominik]

Thanks for all comments!

@Steven_C: You are indeed right; I would not mind a fader that does not reflect the change of a controler value by one unit. I only mentioned this behaviour to may give a hint for the problem that after some 0-1-changes the fader stays in the same position and does not move any more whatever controller message is sent.

I noticed this behaviour several times when I tested my midibox yesterday. Today I was not able to reproduce the error (so I cannot send you a prototypical midi file, Thorsten).

Let's hope everything is going fine now.

Thanks again for your support,

best regards,

Dominik

[Steven_C]

BTW, the panasonics are slightly worse, I think, but since mios 1.4 it acts a lot better. I agree that sometimes the fader dosen't move, for a small distance, probably due to jitter, resulting in an incorrect virtual position, but since TK's awesome feature that can be enabled, that won't send data, until touch sensor is activated, this has not been a problem for me!