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[on:]

Hi im trying to build an Ohm MEter for my project using the analog Pins, I have been following this post from a while ago http://arduino.cc/forum/index.php/topic,21614.0.html but im having some issues.

I am making a sort of object ID system. I have tiles that have a little circuit in them,its placed on a base station. push the button on the tile and the base station read the ID of the tile using the voltage divider rule (each tile has a unique resistance).

What I need in my circuit is this:

This sections is removable        base station
|                                |     |                  |
5v------Resistor--------Switch------10k------GND
                                               |
                                         Analog Read

How should i modify the code from the above forum post to suit my needs?

I hope that makes sense

[Reply #1 on:]

Where is your problem? What does not work?

[Reply #2 on:]

u need a common ground...
i mean: the removable station and the base station must share the same ground potential...
so u need 2 tiles or so...

[Reply #3 on:]

I don't understand, I do have a common ground, don't I? The right hand side of my diagram?

[Reply #4 on:]

I don't understand, I do have a common ground, don't I? The right hand side of my diagram?

oh - ok... i wasnt sure...
so there is a low resistance connection between arduino's ground and that removable object's ground?

[Reply #5 on:]

thats correct

[Reply #6 on:]

then u can just use analogRead()..
when it reads 0 no removable station is connected...
when it reads x (x>0) then a removable station with resistance Rremo=(Vref-Vsen)/Isen (where Vsen=(x*Vref)/1024 and Isen=Vsen/(10kR))...

u can configure Vref via this:
http://arduino.cc/en/Reference/AnalogReference?from=Reference.AREF

[Reply #7 on:]

then u can just use analogRead()..
when it reads 0 no removable station is connected...
when it reads x (x>0) then a removable station with resistance Rremo=(Vref-Vsen)/Isen (where Vsen=(x*Vref)/1024 and Isen=Vsen/(10kR))...

u can configure Vref via this:
http://arduino.cc/en/Reference/AnalogReference?from=Reference.AREF

Ok so if I set Vref to 5v and instead of a 10K known resistance I have say a 3.3K would that work?

[Reply #8 on:]

Ok so if I set Vref to 5v and instead of a 10K known resistance I have say a 3.3K would that work?

yup - sure - it's kirchoff's law... no electron ever violates it... 
http://en.wikipedia.org/wiki/Kirchoff%27s_circuit_laws