New MotorFader design

[Frank]

Hi Thorsten,

I'm confused about the Motor power supply requirements. According to your MBHP_MF_V1 schemetic, the faders should be caliberated at 8V. But i tried adjusting the pot and the range selectable is only from 12V to 17V on my board. If i am correct if one is using a LM7812 regulator you cant get lower than 12V but can get higher voltages with a voltage divider resistors as shown in your schemetic. What is the 8V caliberation level?

I've tried using the new MF design with both Nuendo and Cubase SX and have this weird problem.

This is the setup:-

1.Merger on MF midibox set to OFF

2.both midi in and out of midibox connected to computer

3. Midi Thru in both software set to off.

4. software faders set to transmit movements to    midibox faders.

5. software faders set to receive movements from midibox faders.

I move midibox faders and software faders respond and record the movements.

I playback the song and both software and hardware faders respond.

After a few repeats of the same recorded passage both software and hardware faders stop responding.

If i remove the midi cable from the midibox midi output and restart the same passage both faders respond again. If i plug back the cable , after a few repeats of the song , both faders stop responding again.

I'm still investigating.

Regards

Frank

[LO]

I could be wrong but........

I would have thought the voltage regulator should set the voltage to a constant 12V after that the Pot should trim the voltage down to 8V, I dont see how you would get greater than 12V unless you had the pins on the voltage regulator switched or something???

Are you able to connect a midi monitor to see what is happening with you MF's?

[Frank]

Yeah, thats what i thought too, till i searched and found this :-http://www.southwest.com.au/~jfuller/electronics/regulators.htm

The pot is for control of only the motor movement.

Thanks

[TK.]

Hi Frank,

I'm confused about the Motor power supply requirements. According to your MBHP_MF_V1 schemetic, the faders should be caliberated at 8V. But i tried adjusting the pot and the range selectable is only from 12V to 17V on my board. If i am correct if one is using a LM7812 regulator you cant get lower than 12V but can get higher voltages with a voltage divider resistors as shown in your schemetic. What is the 8V caliberation level?

Damned! Not a LM7812, but a LM317 has to used, otherwise the voltage cannot be regulated correctly. Sorry about this, I remember that my schematic program crashed during I drawed this diagram, thereafter I had to made it again with less motivation - on this way I forgot to update all copy&pasted part values. :-(

So, your MIDIbox MF will work much better with the correct voltages, with > 10V the faders will be moved too fast, so that for example the automatic MIDI feedback elimination routine (which prevents the effects you descriped) will not work correctly.

There is no way without the LM317 - correct fader movements can only be guaranteed with a clean, stable voltage.

Best Regards, Thorsten.

[TK.]

To all beta testers of new circuits: please check the consistency of the PCB layout, the schematic, the part lists first and tell me any differences. Simple typing errors can cause a lot of trouble...  :'(

Best Regards, Thorsten.

[Frank]

Hi Thorsten,

You guys in Europe get soooo many holidays  :D.

Before your last reply i've been testing the MF with only 2 motor faders and the other 6 channels tied to GND. For the motor power circuit, i followed your original circuit except i substituted with a LM7805 and used a 9V AC supply and by adjusting the pot i chose 7.85V for my Panasonic motor faders. They worked very well. Both faders responded concurrently fast and smoothly. The only drawback was i was getting random midi data info for the 2 faders coming out of the midibox midi out port while they were playing back recorded fader movements. I also measured the motor supply voltage while they were moving and it was very stable at 7.85V to 7.86V.

After reading your corrections and downloading the new Supply circuit pdf, i proceeded to substitute with a LM317T and used a 15V AC supply, everything else remained the same as above.  I adjusted pot for 7.85V output and played back the same fader test recording, but surprise, faders did not move. The meter showed voltage unstable from 3.5V to 7V while cubase played and shot back to 7.85V when i stopped Cubase. Also the LCD Display was showing intermittenly "Midi In Overrun, Transm. Aborted". Also random data coming out of Midibox midi out port. I resoldered back to LM7805 and voltage was stable again while faders moved. I resoldered back a second brand new LM317T with the 15V supply and once again unstable voltage, no faders moved and "Midi In Overrun" diplayed again. I doubled check my connections and all soldering but i have no idea what i did wrong. Any ideas in tracing this problem would be much appreciated.

Thanks and Peace to you in this uncertain times.

Frank

[TK.]

Hi Frank,

You guys in Europe get soooo many holidays.

yes  :D

you must know that the LM317 has a different pinout compared to the LM78xx. Take a look into the PCB layout, where you can see, which component has to be connected to which pin.

Random values: you should take care for the connections between the analog inputs of the PIC and the faders. The cables should be very short (less than 30 cm) and shielded to ground. Otherwise the analog signals could be affected by the motor driver signals.

Best Regards, Thorsten.

[Frank]

Hi Thorsten,

Thanks for the info, you were right i took for granted the pinout was the same as a LM7805. Now i have stable motor voltage and stable core 5V voltage but still have same problems of :-

1. Midi In overun, Trans Aborted

2. Midi Feedback elimination routine intermittenly working.

For my knowledge could you explain what are the above error message and routine and what else could cos them not to function besides unstable voltage.

Sorry for the inconvenience but what can I say I'm a Midibox Addict ;D

Frank

[TK.]

Hi Frank,

I never have tested the MIDIbox MF with less than 8 faders, maybe the timer interrupt consumes more cycles in that case and therefore causes a MIDI overrun. I will check this when I'm home again and evtl. release a fixed version.

To 1): this error occurs when the MIDIbox receives a MIDI byte before the last byte has been processed. In my interrupt routines I have to ensure that this case never happens - I will check it.

To 2): The feedback elimination routines are working on the following way: when a fader is moved manually, all incoming events which are assigned to that fader will be ignored for 250 mS - this ensures that the motor doesn't start to run during the manual move.

For the other direction: when a fader has been moved by the motor, no MIDI event will be sent for 250 mS - on this way a feedback (MIDI program -> MIDIbox MF -> MIDI program -> MIDIbox MF -> ...) will be prevented.

Best Regards, Thorsten.

[Frank]

Hello Thorsten,

Ok, the Midi Overrun problem is solved ;D. Thank You.

I've wired up all the eight faders with cables less than 30cm. But i still have the problem of midi data intermittenly being sent by faders only moved by the motors.

That is, if fader1 is assigned B0 00, and the motor is moving fader 1, it will sent out  just a single value

for example B0 00 02 or some other value at another time during automation playback. This happens also to all other faders only if they are moving. It happens intermittenly.

If the automation playback is stopped, the midi output is stable with no jitter or false data being sent.

I'm using Panasonic Faders, could this be in conflict with the delay settings you use in the Feedback elimination routines?

Peace

Frank

[TK.]

Hi Frank,

I changed the timeout algorithm (slightly): up to now, the current fader value is copied into the "target" register during the timeout state after a fader has been moved. This should fix the problem (?)

Link to the new firmware:

http://www.ucapps.de/midibox_mf/midibox_mf_v0003.hex.zip

Best Regards, Thorsten.

[Frank]

Yeesss, the new firmware solved the problem ;D.

Thanks Thorsten everything seems to be working well in my environment.

One question regarding the 74HC595 driving leds, is there any way to get more current when all 8 outputs are driven at once, maybe like a pin compatible substitute for the 595s

Peace

Frank

[TK.]

Hi Frank,

great that it's working - so I can freeze the routines and continue with the next features (Touch Detection for each fader, etc.)

74HC595: normaly it should deliver enough current for 8 LEDs, I don't notice problems with the intensity. However, there are some alternative 74xx595 available, which may be better - I don't have a oversight right here, but I know that there are some informations about the logic families at the TI (Texas Instruments) and Philips homepages.

Best Regards, Thorsten.