Hallo!
Looking at the motorfader schema im a little bit confused.
How do I get 8V when R2 is max 1K?
Uout = 1.25V*(1 + R2/R1)
Uout = 1.25V*(1 + 1000/240)
Uout = 6.5V
Shouldn’t R2 (the poti) be 1.5k ?
Just wondering, Thomas
The formula is wrong, where did you found it?
You need to add an additional part to v_out which depends on the adjusting current and the voltage drop at the pot voltage
Why troubleshooting section? Are you not able to reach the 8V?
I can select the voltage between ca. 5V and 10V. A higher pot value would make adjusting more difficult.
What is the input voltage of your MF module?
Best Regards, Thorsten.
Hi Thorsten!
Yes, I get only 6.8V at the LM317 output. (no H-bridges installed yet)
The formula can be found at
http://www.elektronik-kompendium.de/public/schaerer/ureg3pin.htm (Bild3)
or in the data sheet itself
http://focus.ti.com/lit/ds/symlink/lm317.pdf (page7)
Iadj is 50uA. 1kOhm * 50uA = 0.05V -> neglectable.
I forgot: Uin is 12V.
Thats strange. I just have checked it again, my own MF module is stuffed with a 1k pot
Did you already try another pot (I guess you did? because you always speak in riddles 
Best Regards, Thorsten.
Btw.: I just remember, that the LM317 only works correctly under load.
You could connect a 470 or 1k Ohm resistor between the output pin and ground in order to check the behaviour
Best Regards, Thorsten.
Hallo Thorsten!
I turned the 240Ohm 90°, scrached the circuit path and soldered a 1k R over the scratch so that it is in chain with the 1k poti. I could adjust the voltage now from 6.4V to 10.5V.
The datasheet says 3.5mA is a typical mininal load current.
So I thought the 1.24k is workload enough.
The thing that confuses me is that the formular given in the datsheet says that my 6.5V are consistant with the theory… ???
I must say, that I’m also not sure. I just tried a 1k pot and it worked, therefore I never spent much thoughts on the theoretically best value.
Best Regards, Thorsten.
Success. (with the 1k modification) 
First half (i’m runnig out of BAT54S and TC4427) of the second (I put the first one on the side. because of the code uploading trouble) motor fader board are running.
A little bit slowly but that’s only adjustment.
Hi Thorsten!
Some additional questions:
- It takes more than 1s that all 8faders move from 0 to max.
Two faders need nealy 2s.
In the MF description you list the valus (voltage, duty cycle) for ALPS fader (the first one). But I need more voltage and higher duty cycle.
- The TC4427s are getting relatively hot during working. Normal or not? I cannot use my old MB64 at the moment for comparison.
Hi Thomas,
it shouldn’t make a difference, if one or more faders are moved in parallel, the movement from 0 to max should always take the same time.
One/Two seconds sound very long! As you can see here: http://www.ucapps.de/mbhp/mf/final/rsaon11m9.gif, the fader should reach the target position within ca. 200..400 uS (0.2..0.4 seconds)
It’s not normal that the TC4427 gets hot. Maybe the protection diodes are connected at the wrong way? This would also explain, why the faders are so extremely slow, and why they get even slower when they are moved in parallel.
Best Regards, Thorsten.
Hi Thorsten!
The diodes are not in the wrong direction, but I use BAT54S.
Hi Thorsten!
Do you know how much current the motors actually need?
In the datasheet of ALPS faders http://www3.alps.co.jp/WebObjects/catalog.woa/PDF/E/Potentiometer/SlideMixers/RSN1M/RSN1M.PDF
only a maximum of 700mA is given.
That seems to be too much.
The maximum output current Imax of TC4427 is 0.270A (DIL) / 0.216A (SOIC).
Imax = sqrt(Pmax/10Ohm).
Hi Thomas,
so far I remember, a single motorfader normaly takes ca. 200 mA when driven with PWM, this is what I saw on the ampere meter last time I measured the current drain. Yes, 700 mA is too much, maybe it’s the maximum value when a fader is stopped by hand, but the weak TC4427 will do some saturation here (therefore the reduced max current has an advantage - it saves your PSU).
Which voltage do you read before and after a TC4427 when a fader is moved? And are you able to measure the current?
This afternoon I had the idea to make a small video to demonstrate, how to test the motorfaders with the MIDIbox MF application. It should also give an impression about the fader speed.
The result can be downloaded from this location: http://www.midibox.org/videos/mf_test.avi (11 MB)
Sorry for the “Denglish” (I’ve noticed some wrong words during the playback, but now it’s too dark to record a new video, next time I should prepare a script…)
Best Regards, Thorsten.
“Denglish” hahahah
Thx for the vid TK!
Hi Thorsten!
My faders move with half speed like yours.
But I have no video camera…
And the tc4427s are getting hot after 4x up and down.
Don’t know if this is normal or dangerous.
The BAT54s shottky diodes should work.
What do you think about the pin compatible mic4427 drivers?
I will check this out this week. Today I did some debugging of the other board and found two shortcuts. And completed the software with snapshot functionality and noticed a bug in the event saving routine for bank >1. etc.pp. Theres a lot to do…
BTW. the code upload hardware bug in the other thread seems to be solved. Maybe it was a loose power connection. No problems anymore, even with the increased code.