Re: What are Potentiometers?
I think that the two previous links explain technically how a pot works, but I think that often times people ask this sort of question because they want to know specifically how they're used in FIRST robots. I'll try to do this to add more to this discussion.
To summarize the what's been said, a pot is a variable resistor, and it's purpose typically in FIRST is for some sort of feedback, i.e. knowing the location of a device on a FIRST robot.
On a typical pot you have three wires, a +5 volts input into the pot (out from the controller), a ground wire, and an analog wire that carries a signal 0-5 volts back into controller. At one extreme on a pot, the voltage will be 0 volts, and on the other extreme the voltage will be +5 volts, depending on the shaft location. The robot controller takes this analog voltage signal and runs it through a analog to digital converter (ADC), and expresses this voltage as an integer somewhere between 0 and 1024.
A typical use is having a pot connected to a shaft on a robot arm. As the arm moves back and forth, the whipper on the pot will change the resistance, and hence the output voltage.
Going back to FIRST applications, you can use a potentiometer to have a push buttons on your operator interface move your arm to a known position. So instead of having your operator manually control the arm to move to 50 degrees, with a single button you could have the motor that powers the arm rotate until the controller sees the arm is in position, based on the voltage feedback you get from the potentiometer.
As a disclaimer, there's a whole discipline of engineering with regard to "having the motor that powers the arm rotate until it sees the arm is in position." You can look up some posts on PID control loops in these forums for more information.
I hope this answers your question!
ho ho ho!
Matt
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