Getting a motorized fader working

[Axelch64]

Hi,
i just received a motorized fader that is meant to be use in I think Pro-audiovisual material :
https://fr.aliexpress.com/item/33039705732.html?spm=a2g0s.9042311.0.0.7b706c37LeCkOY
I succesfully got the motor part working with an Arduino motor shield, but I'm stuck with the pot part. It looks like it is a logarithm pot, but I tried, using an ohmmeter to measure the evolution of the resistance along the pot, and it looks more like it is linear. So I don't know if I missed something, I used a simple sketch to see the result which lead me to this issue. Did anyone ever tried this type of pot ?
I don't really have code to provide as it was just displaying the value of the pot on the Serial screen.
Thanks for your replies

[PieterP]

These kinds of potentiometers are usually linear, you don't want logarithmic taper for servo applications.

Here's the code I use to drive mine: Motorized Faders

[gcjr]

see analogRead and analogWrite

const byte pinPot =  A0;
const byte pinLed =  10;

void setup() {
    Serial.begin (9600);
    pinMode (pinLed, OUTPUT);
}

void loop() {
    int pot = analogRead (pinPot);
    int led = map (pot, 0, 1023, 0, 255);
    analogWrite (pinLed, led);

    char s [80];
    sprintf (s, "  %6d %6d", pot, led);
    Serial.println (s);
}

greg

[Axelch64]

@PieterP

These kinds of potentiometers are usually linear, you don't want logarithmic taper for servo applications.

Here's the code I use to drive mine: Motorized Faders

I don't know a lot about those pot, I read that log pot existed and, because it's audio components, I thought it was the same thing. I'm gonna take time tomorrow to read everythings that you sent me, and go from there. I took kind of low cost pot, not like your even tho they look kind of the same, like for example I'm not sure if mine are touch sensitive. If it is too hard for me to work with mine, I'll probably go and buy the same that you got.

@gcjr

see analogRead and analogWrite

const byte pinPot =  A0;
const byte pinLed =  10;

void setup() {
    Serial.begin (9600);
    pinMode (pinLed, OUTPUT);
}

void loop() {
    int pot = analogRead (pinPot);
    int led = map (pot, 0, 1023, 0, 255);
    analogWrite (pinLed, led);

    char s [80];
    sprintf (s, "  %6d %6d", pot, led);
    Serial.println (s);
}

greg

I tried this program, but I still see the same issue that I've got before, I'll try it again tomorrow and see if I missed something. I don't see any reason why your code wouldn't work. I may try to put on a graph the variation of the value that I get centimeters per centimeters to put numbers on what really happens.

Still, thank you both for your help, It's greatly appreciated to get your help.

[lastchancename]

What’s the part number stamped on the pot ?
POT TAPER TYPES

[Axelch64]

It is 011C, which suggest that it is a logarithmic pot, as I'm European, right ?

[PieterP]

In the images of the ebay listing, I see 10KB, which is 10kΩ linear taper.

But the images look like real ALPS faders, which might not be what you actually got if you paid so little money for them.

[Axelch64]

They looks pretty similar indeed. The one that I got looks exactly like the one on the image, and so thought they would be made similar to the ALPS. but yeah maybe the price got me and they maybe worse quality. If I don't find any working solutions, I might just buy a better quality like the one mentioned above, at least I won't havr those issues anymore.

[lastchancename]

Potentiometers made in Asia and the USA are usually marked with an "A" for logarithmic taper or a "B" for linear taper; "C" for the rarely seen reverse logarithmic taper.

Others, particularly those from Europe, may be marked with an "A" for linear taper, a "C" or "B" for logarithmic taper, or an "F" for reverse logarithmic