I'm looking to track the position of a pin on a shape display. I wanted to see if it's possible to make a PCB trace that could be put on the side of the pin and act as a potentiometer to gauge it's movement. Is this feasible, is there any way to strengthen the traces if i use a brush to make contact?
Here's an example of the sort of shape display/pin display that i'm thinking of. An accuracy of ±2 mm is all that's needed.
How much room do you have on the PCB? You could make a meander out of thin (1/4oz?) narrow copper traces, and have heavy pads for the slider/brush to contact. The narrow lines are covered in soldermask to protect them (not shown).
Then you do a 4-wire measurement of the resistance of the meander. You drive current through the meander at the "I+", "I-" lines, and the brush taps off the V+ (using V- as reference). You need a lot of current, and a sensitive milliVoltmeter.
The simple answer is "no".
The problem is that copper has a very low resistance (which is why it's used in wires, right?). This means that for any reasonable current through it the voltage developed will be very small.
In your case, where you apparently want to indicate which discrete location (with a fairly small number of possibilities), it seems entirely possible, as long as you don't expect to use a pcb trace. Instead, you would use a resistor string to act as a discrete-level voltage divider, and make contact with the connection points. It would look something like Martin Stiko's answer, but with resistors instead of meanders.
Might I suggest investigating a solution based on capacitance instead of resistance? Most uCs support capacitive touch interfaces that can be setup for position/proximity detection without much fuss. You can even use it to detect water level. Seems like it migyt be a good fit. Just a suggestion.
