Hey, I got a science project for my major exam and I want to do really well. I think I'll be the only one in the year that will be using an Arduino in my project. I thought of a school project where I will strap on an accelerometer to a medium sized car and put on different bumpers made out of different materials and measure it's G-force during impact. The problem is now is that when I connect the accelerometer to the Arduino and ask it to analogRead the pins, I don't know wether it will return the information in volts, 0-1023 or in G-force?
The Accelerometer output is in volts (millivolts).
That's the simple answer!
Lets say you power it at 3.3V. At 0g it will output 1/2 of 3.3V. It will go higher for positive g & lower for negative. How much? That depends on the range you have it set for.
Lets assume the 1.5g range (most practical for your project).
With that range it will output 800 mV/g, so
-1g = 850mV 0g = 1650mV 1g = 2450mV
Now you will feed this into analog input. Analog input will give Aref voltage/1024. Lets say your Aref is set to 3.3V also (because you set it for external and ran a wire to it from the 3.3V pin which also feeds the MMA7361) so each tick of AnalogRead will be 3.3/1024 or 3.22mV.
Here are the 2 formulas from the above . . .
mV/analogRead unit = Aref V(~3.3) / 1024.0
g = [mV/analogRead unit] * ([units] - ([Aref/2]) / [mvPerG]
Here is the data sheet which could have answered so of this for you . . .
I made some assumptions on things you didn't mention, but principals are all there.
This should get you started. Nice project BTW.
Thanks for your reply, but I still don't get the millivolt/g. How do I know what it will output it as? And if I were to write a code to serial write the g reading from the accelerometer, can you give me a few hints on how to start. Thank You