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Author Topic: 24 motorized fader mixer with Arduino  (Read 15893 times)
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OK, here is what i got as response.
"These were used on multiple different consoles as an aftermarket add on.. I recall several of my customers who used them and I even borrowed rigs to demo at trade shows...

I suspect the small connector is for the audio fader and larger connector the motor drive and servo track.

It may be less simple to chase down motor control interface, and roll DIY control software.

IIRC the cheap alps motorized faders used simple up/down motor, these were more complex IIRC but it's been decades since I've seen or touched one." 

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Another
"Due to the placement of the cables I suspect the circuit on the pcb is a motor driver as opposed to an audio buffer or amp. Aren't the parts assembled on any of your faders? Then you have to build a driver yourself anyway. Simple H-bridges are readily available for cheap and completely integrated, they are easily controlled from any µC using PWM or a DAC if on-board. Depending on the expected supply voltage of the motor and the parts you use you might need an additional level shifter.

Still, I'd try to get hold of some sort of documentation/datasheet. If not for the whole fader, if the motor has a parts number printed on it you might get lucky and find a datasheet at least for that."
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In any case the addition of PWM is unnecessary and complicates the project, no to mention adding audible vibration and possible picked up audio noise.   Who said you need to slow down the slewing at all?  In fact I think the MC33030 chips are either off, full forward or full reverse until the feedback slider voltage matches your control voltage.

Therefore a simple test sketch is in order.  Use two digital pins (A and B) connected to the two motor pins.
Say from your 9v battery test it takes 1/2 a second for the slider to go 0 to full.
In your arduino loop, output:
Pin A High and Pin B Low,
delay 250 ms
Pin B High and Pin A Low
delay 300 ms
Pin B Low

delay 5000 ms
The slider should zoom to about halfway, zoom back,
and then repeat after 5 seconds
« Last Edit: May 11, 2012, 11:32:33 am by Techylah » Logged

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With all this someone had to note the fact that seems only two wires coming out of the motor ?!? If so, should be quite straight forward !!
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With all this someone had to note the fact that seems only two wires coming out of the motor ?!? If so, should be quite straight forward !!
It is actually quite straight forward, I already know witch pins are connected to those two wires, they are the first two of the large pin header. What I don't know is the rest of the pins functions

Quote
In any case the addition of PWM is unnecessary and complicates the project, no to mention adding audible vibration and possible picked up audio noise.   Who said you need to slow down the slewing at all?  In fact I think the MC33030 chips are either off, full forward or full reverse until the feedback slider voltage matches your control voltage.
Digital control is a really good idea, but I have some dobuts on this.  I started using PWM because I thought it would be better in cases of slow movement of the fader. For example, in a 10 seconds fade in. With PWM the servo travels from one point to the other in a constant movement. What happens if I use digital?

Ideally, the servo should be able to move 1/1024 of fader's full length with a digital input. thats like 0,01 cm per step. I don't know if this is possible yet... But I dobut it, is a really small distance

I will try what Techylah suggested today and give you some news soon

Thank you for helping guys
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For example, in a 10 seconds fade in. With PWM the servo travels from one point to the other in a constant movement. What happens if I use digital?

That's a good point, Mytx, but for the full DC voltage approach.   This type of slow fade feature comes out more reliable and more flexible if implemented in software.
You would have a software routine that takes as arguments the index of a stored setting, and a number of seconds with which to fade, and possibly a time increment, probably defaulted to say 100 ms.   The routine would then go in a loop which computes a new temporary set of values, each  n 100ths of the way there, where n is the loop index and repeatedly sets all the sliders to those intermediate values.

That way the overall fade takes exactly 10 seconds in 100 imperceptible steps and you don't have to worry that the fader motors will get stuck if given only 25% PWM.  Or that it is hard to calculate the PWM that corresponds to 10 seconds.  

Another feature (for once you have this linear fade to Settings #3 in n secs command).
You can do a non-linear or exponential fade.  In the above example of a loop 100x, instead of using the loop index "n" for the number of 100ths of the way there,   use "en", where   en = (int)(0.5 + pow (n/100.0, 1/2.0) * 100).
This zooms faster at first and slows down towards the end.   (example:  at index  n=25, which is 1/4 of the way to 100, en is the square root of 1/4, or 1/2 of the way there, or index 50.   You can even change the exponent by increasing the "2.0" for more effect or bringing it down to 1.0 for none or regular linear fade.
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Wouldn't the fader positions be in a MIDI / automation track?  You wouldn't be calculating long-term fades on the uC, that'll already be in the automation data.  You just need to go to a given position.

Well, almost no calculation..  The only interpolation is how long it should take to get there (slew rate) given large or small differences from the current position, and whether there should be any non-linear acceleration applied.
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Wouldn't the fader positions be in a MIDI / automation track?  You wouldn't be calculating long-term fades on the uC, that'll already be in the automation data.  You just need to go to a given position.

Well, almost no calculation..  The only interpolation is how long it should take to get there (slew rate) given large or small differences from the current position, and whether there should be any non-linear acceleration applied.

Youre quite right there. This is not the case of an automated, self sufficient console, but instead one to use with DAW's.
So the console does take care of the audio and the motor translate a given data from the midi automation
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Hello people

Well I've been doing some testing yesterday to understand pinout configuration. The only thing I'm missing is about the touch sensitive (TS) track. How many pins should carry TS singal?
 
Doing some tests in this 3 free pins I just got a 3 milivolt difference between touched and untouched status of the TS (feeding sensor with 3.3v from Arduino. Is too small difference, dont you think? Maybe is enough to pick it up with AD7147 chips Techylah reccomended?

I've been calling many electronic shops here but no luck with MC33030 chip... I may order it in united states and try to ship it, but if i get an alternative chip with similar functions in Argentina is way easier.




* mtrfdr pinout.jpg (331.09 KB, 1000x470 - viewed 87 times.)
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I just got a 3 milivolt difference between touched and untouched status of the TS (feeding sensor with 3.3v from Arduino. Is too small difference, dont you think? Maybe is enough to pick it up with AD7147 chips Techylah reccomended?

I suspect that the 3mv may just be noise pickup, with body acting as an antenna.  This is unreliable and is why capacitance sensing is used.

If you can't get the AD7147, which is a special purpose single-sourced chip, perhaps you'd like to roll your own capacitance sensor.
This circuit uses the much more available hex schmitt trigger chip, 74HC14, but uses a bunch of additional components.  Since you are using multiple sensors, you can save and have them all share the oscillator in the top part of the schematic.  They would all need their own lower part, the part that includes "touch button".
http://www.discovercircuits.com/DJ-Circuits/5vmom1.htm

Alternatively,  this wiki page lists some other difficult-to-get chips.
http://en.wikipedia.org/wiki/Touch_sensor
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Hello again people.

Well, is taking me too long to find the chips I need here in Argentina.
I will keep trying to get them, and that would be all I need to pick up all the data I need from the fader, and controlling the motors.
That's almost everything concerning to hardware.

While I look for those chips, I will start research about MIDI and OSC communications to see witch one fits better on the project.
This controller should be recognized automatically as an instrument by the software (protools or other DAW). Software MIDI input/output should make the work of reading/writing MIDI. Touch sensor from the fader should GATE the midi messaging from software to Arduino. That way, when fader is in use, their motor stops working.
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It will never be automatically recognised by the DAW, mind... Will always need configuration on the DAW settings, just like any other midi instrument, controller, etc...
By the way- For those who asked where to find motorized faders= I have close to 30 of them for sale (both linear and log type), brand new, never used, still wrapped. Sold quite a few already,and seem to be flying out the door so let me know if you want any !!
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Well! it's being a long time since my last update.

News:
- Got the DC motor spining both sides with a simple arduino program and a H bridge (L293D)
- Decided to communicate DAW and faders vía OSC.
- Tried and tried to get MC33030 chip with no luck. I will need to use PID in Arduino to tell the motor where to turn.
- No luck with Touch Sensor reading... No chip to pick un capacitive sensors in my city... I may have to do it myself.

I will keep on this until I have a solid outcome.
I hope I have some time this week to start sharing the code I'm writing for it. PID may turn a little complex, as well as PWM and sound frequencies.

cheers
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I dont know much about OSC, but why the choice ?
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Actually, I just read I can't use OSC to directly communicate pro tools and Arduino.

some info about MIDI vs. OSC here http://www.ucapps.de/midibox_seq_manual_osc.html



So I will need tu use midi. The goal now is to communicate protools and arduino with a 1024 steps MIDI CC messages. I guess there is a lot of that in this forum.

:smiley
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