2 meters long potentiometer with resistance wire


I am doing a school project which consists of controlling the position of two trains.

I decided to get the position of each train by using a resistance wire (63ohm/m) and using the arduino boards as potentiometers. The wire will follow the rails, and at the end of the rails, I Will use copper cable to connect it with the - of the power supply. The boards will be connected to the resistance wire and to the copper wire. Here is a diagram which shows how It looks like in my mind:


As I don't know much about Arduino, I would like to know your thoughts about the feasibility of this project, especially: Will the first Arduino board create a short-circuit ?
Is there a limit to the current that the arduino's digital input can handle ?

Thank you for your answers.

You do NOT need an Arduino to test your project. Use your volt meter in place of where you have the Arduino shown in the diagram. That will quickly tell you if it will work or not!

I thought about that, but I have learnt in physics that the voltmeter is "theoratically" equivalent to a resistor with inifinite resistance. Would the Arduino board operate the same way ?

Yes. Theoretically. :wink:

okay, thanks to you two!

How is the train connected?

I intended to use contact brushes that are normally used in toy cars like this one:
Amazon.com: Carrera 20365 10 Pack of Double Sliding Contact Brushes for Evolution/Digital 124/Digital 132 Slot Cars : Toys & Games

What do the brushes contact? Can you draw it? One brush to the wire, and the other one to ???? what?

No, the Arduino does not create a short circuit. Analogue Inputs (and Digital ones) are a high resistance.

Whether it will work satisfactorily or not depends on how good your sliding connections are.

Incidentally the symbol you have used for your 5V supply is the symbol for a

Likely to the third rail!

the brushes contact wires which will be set between the rails

:slight_smile: come on, I'm serious...

Yes, but which wires? You didn't really answer...

So am I . The op just wrote he is making the third rail from copper wire.

both the resistance wire and the copper wire. They will be powered and welded together like on the diagram

Oh, man... and does the train short the two wires together, i.e. connect them through the brushes?

No the train won't short the two wires. Wouldn't It shortcut the rest of the circuit and disallow the 2nd Arduino to read the tension ?

So what will the wires do? Power the train?

Sooner or later, the OP is going to have to actually test his project. The sooner the better!

Yeah, but resistance wire is expensive. Maybe we can save the OP some money...