What would be the best type of potentiometer would be best to use? We have no use yet, we just want to get some so I can figure out how to wire and program them. If you guys could send me links to the ones you guys use that would be great.
For something just to play with, grab whatever is available at your local Radio Shack. You’ll want to learn the difference between linear and logarithmic potentiometers (linear ones tend to be a little easier for the software guys to work with, for what we’re doing).
Once you’ve got that down and know how to work with them, the rest is just going to your favorite on-line site (like digikey) and ordering exactly what you want for your needs. For example, you can get a potentiometer that has 270 degrees of rotation, with tops built in on either side. Or you could get one that has 360 degrees of rotation with no stops, so it basically repeats when you go past 360. Or you could get a mutli-turn which gives you many full rotations (this past year we used a 10-turn potentiometer… that means 3600 degrees of rotation to go from one extreme to the other).
Keep in mind that matching the rotation of the potentiometer to the actual rotation seen in your mechanism is important. If you have a mechanism that only turns 200 degrees, a potentiometer with a 270 degree rotation will give a signal output using most of the available range - in other words, in the code they’ll see values across most of the range provided. If, on the other hand, you use a 10-turn potentiometer then most of the range is completely wasted. In this situation the difference of 0.1V could be a significant amount of travel for your mechanism!
For what it’s worth, I have no part numbers for most of our potentiometers… we picked up an unlabeled bin full of used ones from one of our sponsors and sorted it by number of turns. It’s good enough for most of what we do, and when we have something specific, we’ll go to digikey and do some searches until we find something that fits.
My personal favourite is this (select analogue from the options).
Oh, and pick a value of maybe 10kOhms. much higher and noise becomes a factor, much lower and too much current is drawn from your power source. The Radio Shack ones are just fine for 95% of what you’ll be doing.
For a [strike]Digital Sidecar[/strike] Analog Breakout, one outer leg of the pot goes to +, the other outer leg goes to -, and the center leg (“wiper”) goes to SIG.
Last I checked, pots get wired to the analog breakout and not the digital sidecar.
Yes, you are absolutely correct. I was thinking of a limit switch when I wrote “digital sidecar”, but of course an analog potentiometer goes to the analog breakout. :o