Pot value minimum not zero

Projects General Guidance
1

Hey everyone. I have a bit of an issue with my circuit. It's an RGB color picker with three potentiometers, an LCD display, an RGB LED, and a pushbutton. The button and the potentiometers are connected to the same GND, and the LCD and LED are connected to the same GND too. The issue is that the potentiometers won't go all the way down to zero. The minimum value isn't constant either

Here is an image of my circuit: 20181130_221000.jpg - Google Drive

I would appreciate any help.

Thanks,
Carson

2

cwduffy01:
Hey everyone. I have a bit of an issue with my circuit. It's an RGB color picker with three potentiometers, an LCD display, an RGB LED, and a pushbutton. The button and the potentiometers are connected to the same GND, and the LCD and LED are connected to the same GND too. The issue is that the potentiometers won't go all the way down to zero. The minimum value isn't constant either

Here is an image of my circuit: 20181130_221000.jpg - Google Drive

I would appreciate any help.

Thanks,
Carson

Have you checked the potentiometers with an ohm meter? How close to zero do they go? Did you buy them all from the same place? Did you buy a named brand or from a company that specified they would go to zero?

And more to the point, did you try connecting them the other way around to see if the slider would go to zero on the opposite pin?

Paul

3

Are all of those grounds connected together and to the Arduino ground?

4

Things are not perfect in the analog world. How low do they go? If you're down to 10 out of 1023 that's only 1% and that doesn't seem too bad...

You might have to write your program so it doesn't have to go to zero... Maybe use the map() function. If you don't individually "calibrate" all of the pots there could be some small movement near zero (near fully counter-clockwise?) where nothing happens but that shouldn't be a huge issue.

5

Paul_KD7HB:
Have you checked the potentiometers with an ohm meter? How close to zero do they go? Did you buy them all from the same place? Did you buy a named brand or from a company that specified they would go to zero?

And more to the point, did you try connecting them the other way around to see if the slider would go to zero on the opposite pin?

Paul

The resistance on the potentiometers range from 3.9 ohms when turned down and 4.75 kOhms when all the way up. Their lowest values can be anywhere from 5 to 60. I found them from amazon and they are made by a company named uxcell. They have gone down to zero before. I've tried connecting them the other way around too and that didn't work

groundFungus:
Are all of those grounds connected together and to the Arduino ground?

They aren't all connected to the same ground pin. The LCD and LED are connected to one pin and the button and pots are connected to another.

6

If you are serious about your pots getting to zero at one end and will continue to do that for ages, get some from a stocking distributor like Digikey or Mouser, etc. Yours are using a conductive plastic strip and seems to be subject to wear.

Paul

7

Paul_KD7HB:
If you are serious about your pots getting to zero at one end and will continue to do that for ages, get some from a stocking distributor like Digikey or Mouser, etc. Yours are using a conductive plastic strip and seems to be subject to wear.

Paul

Okay. Is there a specific brand you recommend or will anything on either site work? There are a few distinct types, such as conductive plastic or wirewound...

8

cwduffy01:
Okay. Is there a specific brand you recommend or will anything on either site work? There are a few distinct types, such as conductive plastic or wirewound...

Any will do as long as specified 0-to-your max value. If it does not go to zero, return it.

Paul