I would like to learn how to read amp/current flow from a power source using my arduino. I was able to set up the arduino to read volts and display it on my serial monitor with no problem. My research on reading current flow with my arduino led me to using a couple resistors as a shunt. This is where I hit a brick wall. How do I "make" a shunt resistor from resistors and what would the sketch look like to be able to display the information on my serial monitor inside the arduino program.
I made a dual axis heliostat with my arduino that works awesome and I would like to be able to eventually monitor its output wirelessly via a couple Xbee's. Like I said earlier, I was able to figure out how to monitor voltage output with the arduino but I am hitting a brick wall with the amp monitoring part. Any diagrams or sketch's in your responses would be greatly appreciated as I am a visual learner. My solar cells output roughly 2.5V/600ma so I need to be able to read current down to about 75-100ma and up to 600ma.
To employ a shunt you want a low value resistor in series with the load.
This resistor should be small in comparison with the equivalent load resistance.
You measure the voltage across the shunt; as you know the shunt resistance you can convert this to current via Ohm's Law, i.e., I = V/R
Just been searching for heliostats and came across this page. In case you're interested, I modified some C++ code for the arduino to track the sun. Just requires an RTC and some set co-ordinates then it'll tell you where the sun is!
Squeeeee!
To employ a shunt you want a low value resistor in series with the load.
While technically true, and probably good enough for most purposes, a true shunt resistor is made from a special metal called Manganin:
...mainly because it is stable in resistance over time and temperature, whereas a standard resistor is not. So, if you want accurate measurements, you need to use a real shunt resistor, and not a standard resistor.