Hi,
I'm trying to read values from a softpot potentiometer and the values are quite accurate, except when nothing's touching it.
I should be getting a value of 0 then, right? Except I'm getting a floating value of ~700.
I've seen someone recommend putting a large resistor (100k, 330k, etc) between the ground and the pot, but that hasn't worked. It's just lowered the floating value, and reduces the range of values reported.
Any advice? Thanks.
I should be getting a value of 0 then, right?
Wrong. The input will float and you should get what you do get.
a large resistor (100k, 330k, etc) between the ground and the pot, but that hasn't worked
What exact value did you use? If it doesn't work the try a lower one, it will eventually work. You can also add a 0.1uF capacitor on the input to cut down on the noise.
I tried every standard resistor I had larger than the 10k of the pot.
So, 22k, 33k, 47k, 100k, 220k, 330k, 470k.
All of them either simply changed the floating value, reduced the range or (usually) both.
reduced the range
Yes you will reduce the range, that is only to be expected. The trick is to find a value that minimises the reduction in range while still giving you zero on no contact.
I none of the ones I mentioned gave a zero on no contact, otherwise I'd have just dealt with it. =\