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Topic: Project 5 (Mood Cue): Highly variable Potentiometer voltage? (Read 4831 times) previous topic - next topic

revanMalak

I created project 5 (mood cue) and have noticed my servo was moving somewhat erratically. Looking at the console logs I see that the voltage difference and angle are cycling through values (0-1023 for voltage difference, and 0-179 for angle), without touching the potentiometer, very quickly; it may go through 30 degrees in a few seconds. I was stumped on that for awhile, so I rebuilt the circuit and the difference was much smaller (cycling between ~10˚ without touching the potentiometer); then later, it went later went back to cycling between larger numbers.

1. Is this expected behavior? Or is it expected that the potentiometer value and angle are (mostly) constant at rest? Could using a USB-A to USB-C adapter on a laptop be causing this unsteady voltage?

Because it's changing values so quickly the servo is never really at rest; it's always moving around a little bit. Would that jerky movement damage the servo? I found a video on youtube (https://www.youtube.com/watch?v=p6m8jOi7wgM) of someone else making the same project, and I was surprised to see that their servo was basically motionless when the potentiometer wasn't being touched.

2. The potentiometer seems to get loose very easily; I have trouble turning the dial without the whole thing getting lose or coming out of the breadboard. Is that expected? (I am surprised in the video above that the individual was able to move the dial fairly easily). Could the loose pontentiometer be causing the cycling voltage?

What I've tried:

- Rebuilt circuit using a different potentiometer (without bending the feet so much)
- Built a circuit with just the servo going back and forth from 0-179˚, to prove the servo would work fine with the same USB power (I did this because some posts online mentioned that using external batteries is preferred for servos)


Side question:
3. How do you determine how much capacitance is needed in a circuit? In the book they use 2 capacitors, but don't explain any formula. I looked here but didn't find an answer:
https://forum.arduino.cc/index.php?topic=438954.0

Thank you!

pingi_j

Hello,

Answer to Q2: I had the same problem. For me it worked if I plugged in the potentiometer much harder so that it was stuck. Try to rotate the potentiometer 90 degrees and plug it in, then you will se how far down it can go. In that direction it's easier for the potentiometer to get plugget in but once you know how far in you can plug it push it in the correct way (hard but without breaking anything).

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