Hi All,
My question might be very simple for some of you. I have an Arduino Uno, and I want to read a potentiometer. Very simple. The problem is the noise. Is there any way that I decrease the noise? For example, when the potentiometer is fixed on a value, I don't see any fluctuation (even small ones) in the serial monitor.
Thanks
Is the potentiometer a new one? How do you have it wired? Is you "noise" only when moving the slider on the potentiometer?
you can decide to ignore some of the least significant bits
by dividing
int stableValue = analogRead(A0) >> 2;
or just canceling out the LSbs you don't want
int stableValue = analogRead(A0) & 0b1111111111111100;
Yes, it is. The noise is around 10-20 in the range of 0 to 1023. But I don't want this as well. I want a fixed number when the slider is fixed.
No, I can see the noise even when the slider is static.
And it is wired how?
Great thanks J-M-L. It worked perfectly. But could you please explain a bit about the code you sent me and how they function?
Thank you
basically you read the value but you ignore what's going on in the low bits.
with the & 0b1111111111111100 masking you nullify the 2 low bits (corresponding to 0,1,2 and 3)
➜ if you read 0, 1, 2 or 3 you'll see 0
➜ if you read 4, 5 ,6 or 7, you'll see 4
➜ if you read 8,9,10 or 11, you'll see 8
etc
with the >> 2, it's dividing by 4
➜ if you read 0, 1, 2 or 3 you'll see 0
➜ if you read 4, 5 ,6 or 7, you'll see 1
➜ if you read 8,9,10 or 11, you'll see 2
etc
Be aware of the noise during conversion... I've used the adc a lot, but have never had a noise problem.
The datasheet for the 328p states ... section 23.6
"The ADC features a noise canceler that enables conversion during sleep mode to reduce noise induced from the CPU core and other I/O peripherals."
I would think you have something lose or not properly connected. As @Paul_KD7HB has stated... we need a schematic.
If the 'pot' on your input is of a reasonable value the impedance is low, so noise from the pot is probably not the issue.
If you have problems with the noise you might have to put it to sleep during the conversion for the lowest noise ... I'd look elsewhere first.
Good luck
The schematic is very simple. Three wires from Arduino (GND, A0, and 5V) are connected to a potentiometer through a breadboard. Could you please explain a bit more about the noise reduction through this sleep mode? I have never heard of it.
Please see this video at the selected moment. There are noises when the pot is static.
https://youtu.be/t9DEAreCD3g?t=265
I guess you were asking @jkwilborn
Yes. You are right. Sorry.
I watched the video, I think you have some kind of mechanical connection issue...
What is the ohm value of the pot ... 10k ... same as the video?
You should not need to do anything with the sleep issue with this setup... However, I'll include the link to my copy of the 328p datasheet. I posted the section previously... 23.6
I think you should check your connections and pot ... something is changing or you wouldn't read different values with it static.
Good luck
The last time I read the long data sheet, that referred to the CPU being stopped for two cycles while the A/D conversion takes place. It is automatically done each time, not a programmed "sleep" mode.
Add a 100nF capacitor from wiper to ground.
From the posted document...
23.6 ADC Noise Canceler
The ADC features a noise canceler that enables conversion during sleep mode to reduce noise
induced from the CPU core and other I/O peripherals. The noise canceler can be used with ADC
Noise Reduction and Idle mode. To make use of this feature, the following procedure should be
used:
Note that the ADC will not be automatically turned off when entering other sleep modes than Idle
mode and ADC Noise Reduction mode. The user is advised to write zero to ADEN before entering such sleep modes to avoid excessive power consumption.
I read this as a suggestion to reduce noise during conversion... no?
I don't think they have a need to go this far for such a simple configuration...
My guess is that the root cause of the problem is due to the way that you have wired up the potentiometer. Individual wires will pick up 50Hz or 60Hz (dependent on your territory) mains 'hum'.
This means that the wire from the wiper to the analogue input will have the required signal with a 50Hz/60Hz signal superimposed on it. Because the Arduino's ADC takes an instantaneous reading, then the result will vary depending on where abouts in the mains cycle the conversion takes place.
You can reduce the mains hum by using screened cable or you could twist the three wires together.
You can reduce the noise as suggested.
Another thing to keep in mind is adding some hysteresis to your analog input code, so the reading won't change until the pot has moved a certain amount away from the last reading.
This works better in some cases than simply chopping off the bottom bits, as it would eliminate the fluctuations that would still occur when near a transitions.
newReading = analogRead(signalPin);
if (abs(newReading - currentReading) > 15)
currentReading = newReading;
would stick with the old reading until you'd scootched the pot a bit.
I hope, can't test that code from right here.
Google hysteresis and find @6v6gt's very thorough tutorial:
HTH
a7
Or take an average of multiple readings spread across one full 50 or 60 Hz cycle. .
That should not happen.
+/- one value, yes. But not 10-20.
Hardware problem.
Don't try to fix with software. Find the problem.
Leo..
Makes you wonder what ACTUAL code the compiler generates for the analog read.