Hi There!
Working on simple Arduino project. Got my pots working but values are fluttering a bit. Would a bypass cap on my power supply (4.5V 700mA) ease the problem? If so, what would be a good value? I checked postings regarding bypass capacitors, but they mainly related to IC use. Thanks!

Best,
-M

 

Try 1μF capacitor on the output of the pot, across the analog input pin of the Arduino and GND.

 

Cool, thanks. To be clear, ceramic capacitor? And also, can I attach this cap on circuit board away from the knob itself or is it better to have the cap as close to pot as possible?

 

Cool, thanks. To be clear, ceramic capacitor? And also, can I attach this cap on circuit board away from the knob itself or is it better to have the cap as close to pot as possible?

Ceramic is fine.
Electrolytic is ok so long as you watch the polarity. Negative lead goes to GND.

You want it close to the Arduino pin. Actually as close to the Atmel MCU input pin as possible.
I am not saying it is going to work. All I am saying is give it a try and see if it makes a difference.

 

Cool, thanks. To be clear, ceramic capacitor? And also, can I attach this cap on circuit board away from the knob itself or is it better to have the cap as close to pot as possible?

Typical ceramic caps are rare above 0.22uF, I've seen brochures for multilayer ceramic chip capacitors with values up to 180uF - out in the field, 22 & 47uF aren't completely rare.

Pretty much any type of cap is OK for cleaning up the voltage from a pot. Although rare - some cheap electrolytics can be just as noisy as the pot. Tantalum caps should be avoided if there's *ANY* possibility of reverse voltage being applied.

For the output from the pot; somewhere around 0.1uF - 0.22uF should suffice. The microcontroller board should already have adequate decoupling, but its common practice to parallel multiple decoupling capacitors to tackle different noise bands. You should find electrolytics of at least 47uF, and usually more than 1, there should be several caps around 0.1uF - 0.22uF for digital hash, ceramic is one of the best types for low ESR. If the noise extends in the direction of RF; you could try adding a few 0.001uF or 0.01uF.

 

One thing that also needs to be considered is the stability of the voltage that is being used for the analogue reference voltage. Is your 4.5 volt supply being used for the analogue reference or is it fiirst being regulated down to 3.3 volts. You need to know what the reference voltage so you can calculate what one bit from the A to D represents. if you are using the same voltage to feed the potentiometer as the analogue reference then the actual value is less important.

Les.

 

Thanks everyone for the information. I'll try some of these out and report back. Appreciated!!!