Wiring A Potentiometer
 

I wired a potentiometer to the analog breakout, I am reading voltage from it in Windriver c++ but for some reason the analog breakout gets extremely hot and the green light on the analog breakout turns off anytime the knob on the pot is turned all the way down.
did I wire it wrong or something?

Re: Wiring A Potentiometer
 

Post the part number of the pot, and a close-up picture of the wiring (at both the pot end and the analog breakout end).

Re: Wiring A Potentiometer
 

Sounds like it's wired wrong. Power it down. Let's see a sketch of what you have.

Re: Wiring A Potentiometer
 

Occam's Razor suggests "yes, you likely wired it wrong"

Potentiometers have 3 terminals, two between the ends of a resistor and one that contacts the resistor between the ends (typically controlled by the shaft).

If you have a 5kohm pot, there is 5kohms between the two ends, regardless of the shaft angle, and the resistance between either end and the wiper varies based on shaft angle.

You connect the two ends across power and ground (red and black) and connect the wiper to the signal (white) [respective to a white-red-black servo wire]

What it sounds like is you wired power and ground to one end and the wiper. As you rotate the wiper towards one end, the resistance goes down, current goes up, and eventually the supply craters due to excessive current draw.

Re: Wiring A Potentiometer
 

http://imgh.us/DSC_00601.jpg

Underneath the pot, it marked "D5K"

Thanks, I re-wired it properly this time, I confused with the whole resistance distribution and location of the wiper

Re: Wiring A Potentiometer
 

Now we need to see where the red, white, and black wires are connected on the other end:

... If the red wire is power, that is INCORRECT.

BTW, you need to get rid of those wire whiskers.

Re: Wiring A Potentiometer
 

Seriously, have someone take a closer look at that. It's asking for trouble. You'd be well advised to inspect all the other solder joints (and crimps) on the robot too.

Re: Wiring A Potentiometer
 

I agree with Ether. That soldering job is pretty rough looking, and yes, in competition, I would expect to see smoke emitting from it at some point.

Invest in some soldering flux, leaded solder (60/40 with rosin core is my favorite), and some heat shrink.

Remember to put the heat shrink on the wire before you solder it, and make sure it is away from the soldering point while soldering, because it will shrink down with very little heat. I know this seems like common sense, but I can't count how many times I've done it, and I will guarantee that I will do it again in the future.

Leaded solder, of course, has lead in it. No, you won't get any diseases from using it, but you should thoroughly wash your hands with soap and hot water, ESPECIALLY before eating.

Here's how to properly solder, or at least my preferred way, and I'm pretty good if I do say so myself. :cool:

Apply a small dab of flux to the terminal and wire after you feed it through the potentiometer holes (again, don't forget the heat shrink!!!). If you get too much flux on, that's fine. The more, the better... err... you won't hurt anything by having too much.

Apply a small bit of solder to the iron. This will be used JUST to help aid in heat transfer.

Touch the iron to the terminal and allow it to heat for a few seconds (2 or 3 seconds should suffice). Solder won't bond unless both the wire and terminal are heated up enough. You'll notice the solder you applied to the iron 'flow' to the terminal once it's hot enough.

At this point, feed some more solder in to make a nice, smooth joint.

Inspect the solder joint for any bubbles, cracks, or anything out of the ordinary.

Allow the joints to cool, and then slide the heat shrink over the terminals to insulate them.

Use a heat gun to shrink the heat shrink. If you don't have one, you can use a flame of some sort, but be quick and spread the heat. Heat shrink, like anything else, will catch on fire if it gets hot enough.

If you don't have heat shrink, then insulate it with electrical tape. Just insulate it somehow. Signal wires are a magnet for shorting.

Re: Wiring A Potentiometer
 

(Bold emphasis mine.)

Interestingly, the origin of the word flux, fluxus from Latin, meaning "to flow".

-Scott

Re: Wiring A Potentiometer
 

Nice! I was never curious enough about it, but now I know. :D

Re: Wiring A Potentiometer
 

Swap the red and white wires.

-Hugh