Hi all,
I've been looking into using the analog read serial function(https://www.arduino.cc/en/Tutorial/AnalogReadSerial) and this guide says that it reads a 10k pot.
my question is, is that the only value an Arduino Mega 2650 can read, or will it read the full range of a 23k pot like that use in a linear actuator for position sensing? as seen here for the 200mm actuator feedback http://www.robotshop.com/media/files/pdf/P16_Datasheet-2.pdf
Can you quote the sentence where it says that it reads a 10k pot ?
Have you read it ? The analog pin reads the analog voltage. It reads a voltage, not a pot.
Koepel:
Can you quote the sentence where it says that it reads a 10k pot ?
Have you read it ? The analog pin reads the analog voltage. It reads a voltage, not a pot.
nope i haven't read it, my uncertainty arose from the tutorial using a 10k pot. So what you're saying is that it will read the voltage and give an indication between 0-1023 on the analog input?
Of course I read the article, just not the specific “must use a 10k pot”. Hence my confusion.
A 23k pot will do just fine - though you shouldn't go too much higher in value. The ADC works best with signals that have <10k input impedance, with your pot you're right around that number. Note that this is not a hard limit or anything, but if you go much over (e.g. using a 100k or 1M pot) you may experience slowness in reaction of the ADC or less stable readings.
If too low a value (<1k) you get a significant current between the +5 and GND through the pot. At 1k you're leaking 5 mA through that pot.
This is why 10k is a very commonly used value. Low current leakage (0.5 mA) while still providing a strong signal to the ADC.
Other than that, just about any pot will do fine - use whatever you happen to have. Wire between GND and +5V and the ADC connected to the slider contact. That gives you the 0-5V output you need.
This is one of those places where "about 10k" is fine.
Too much higher, and the limited current flowing into (or is it out of? Whichever, it is LIMITED (small)) becomes big enough to "count" in the overall picture, cause problem.
Use a much smaller pot, and whatever is putting 5v in at the top is going to have to supply quite a bit of current. This can strain the power supply... none can supply infinite current, they all have save maxima... and if your power supply is "up" to the current that will result, it may be that the potentiometer doesn't (They too have limitations, otherwise known as maximums.) (With a smaller pot, the current to/from the Arduino pin is insignificant in the bigger picture.)