Connected a potentiometer, did I damage something?

When testing my Arduino Mega's analog input, I discovered that it only read up to about 928 rather than the expected 1024. So to see if it was the resistor I had inline with the 5v input of the Potentiometer, I pulled the resistor out, and connected the potentiometer between 5v, 0v, and Analog input 5. The Potentiometer was full over to 5v and I didn't realize it till I looked at the board and the lights were off. I yanked the Potentiometer and the lights came back on. I didn't see any smoke, or sense anything overheated, but I'm now a tad nervous.

Also, the original problem, I've since tested the potentiometer with a multimeter (should have done first) and found that for about 60 degrees of its 300 degree range, it delivers maximum resistance (or minimum if turned around) thus I get either 928 or 0 for 60 degrees of the shaft's travel leaving me with 240 usable degrees. It's a radio shack 271-1715 10Kohm Linear taper and it looks like with some careful needle nose pliers work I could open it and adjust something, but would it even be possible? Thanks for any help! Matt

[EDIT]I went ahead and opened up the potentiometer, and discovered the problem. The resistance coating on the metal strip inside the unit is incomplete. Technically though, it is within the advertised tolerance of 20% so I can't take it back for a manufacturer's defect, and I can't hold them to the 300 degrees because the specs don't say function over 300 degrees, just rotation over 300 degrees. I guess I'll just have to treat the potentiometer as if it were a 240 degree unit any ways.

Well as long as you only had wired +5vdc to the pot there is not way to damage a analog input pin as they have very high input resistance. You can however miswire the pot such that you short circuit the +5vdc at some pot position causing the on board +5vdc voltage regulator or the USB thermofuse to go into protection mode, powering down the board until the condition is cleared.

Most standard pots only work over around a 270 degree rotation +/-. You should however be able to get a full 0-5vdc voltage range over that travel.

So is your application to generate a variable voltage, or are you wishing to measure some angle change by coupling the pot to something that turns?

Lefty

The resistance coating on the metal strip inside the unit is incomplete. Technically though, it is within the advertised tolerance of 20% so I can't take it back for a manufacturer's defect,

But it is not acting as a pot so technically it is a defect. It the U.K. we have the "trade descriptions act" which says any description of a product for sale must be true. One of the very few better pieces of legislation we have.