Hi All,
I am new to using an arduino, but have been looking at other peoples projects for a long time. While I have seen how versatile these little units are, for the most part the sensors which people seem to use are conventional electronic components where they tend to be totally wired into the circuitry rather than a common earth.
I was wondering if there is a universal way of connecting sensors which have a common earth thats not the arduinos?
Basically my project consists of having a digital display read out from 4 -5 automotive sensors (on an old camper van) consisting of things like oil/water temperatures, leisure battery voltage, maybe fuel level and maybe oil pressure.
Now as far as I can work out all the devices except voltage reading are just a resistance, whether its a thermistor or potentiometer(as the case of the fuel sender I think). I looked at a few diagrams of how the analogue sensors work on the arduino but from the diagrams it looked like it had to be a closed loop, where you had a 5v supply into one side of the sensor, the other side went to the analogue input and also connected to earth with a resistor in between. My problem is that something like the water temperature sensor screws into earth and has a 1 wire connection, I couldnt work out if it was possible to just swap the resistor into the place of the sensor and sensor into the place of the resistor on the circuit (the standard input one on here) ? By doing some maths I figured this would just give you a reverse reading and you would have to program accordingly?
With the voltage sensing I had a look around and found its possible to do using an optoisolator on the right of this diagram:
http://www.arduino.cc/playground/uploads/Learning/Level_shifting_4_arduino.pdf
so I was looking at the diagram on the right and from what I understood the circuit can sense 12v+, with the arduinos direct sensing method being just 0-5v. I was thinking as a universal method of sensor connection, you could use something like a LM7812 voltage regulator to provide a constant 12v(as vehicle voltage tends to be 12-14.2v when running) and rather than have the resistor on the input to the optoisolator, just connect the ground on the input side to my resistance based sensor? I figured that the voltage would then rise/fall according to how much earth resistance there was.
Maybe I am getting a little complicated!
my background isnt electronics, I find I deal with them more and more and can see alot of potential and am keen to learn!
Cheers for any assistance anyone can give in advance
