retrolefty:
RogerW:
I have a new project in mind for an Arduino. I would like to measure current and voltage from a LiPo type battery. I would like to measure the unloaded voltage of the battery which should be pretty simple. I would then switch in a load and measure the battery voltage and the current to the load. I have a current shunt which I could use but I am concerned about the input impedance of the analog input to the chip because I will be measuring about 8 amps thru the shunt. I don't want that much current trying to find a path thru the chip.Any thoughts on my idea and if it is safe to do?
RWW
Just because of the very high DC input impedance of a analog input pin you will have no problems about having to worry about current finding a path through the analog input pin. The only requirement is that the shunt must be 'ground based', that is one side of the shunt must be directly wired to both the power source ground being measured and wired to a arduino ground pin. Then the 'high side' of the DC shunt can be wired directly to a analog input pin. Just be sure the ohm value of the shunt resistor is such that it won't develop more the +5vdc at the maximum current value, as that is the electrical voltage limit for an arduino analog input pin.
Lefty
Thanks Lefty. I had concerns about the input impedance. I also thank you for your suggestion on how it needs to be hooked up. Your answer reinforces what I was thinking needed to be done.
RWW