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Topic: Ohm Meter Issue (Read 1 time) previous topic - next topic

ricadam

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


pylon

Where is your problem? What does not work?

RIDDICK

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...
-Arne

ricadam

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

RIDDICK


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?
-Arne

ricadam

#5
Nov 08, 2012, 03:26 am Last Edit: Nov 08, 2012, 07:55 am by ricadam Reason: 1
thats correct

RIDDICK

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
-Arne

ricadam


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?

RIDDICK

Quote

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
-Arne

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