I²C Voltage-Current-Power INA219 Sensor

Lower power consumption is the next frontier, but how to measure it? Using many sensors and actuators may easily overload a voltage regulator. 

The INA219 is an all-included voltage-current-power sensor. It uses the I²C bus.

I built this Volt-Amp-Watt-meter with a MSP430G2553 and Energia.
Current is calculated using a shunt, in my case, a 0.1Ω 1% resistor.

The INA219 does all the calculations for the power itself, by multiplying voltage by current internally. ​
The only remaining operations concern the scaling.
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The package is a SO-8 with a 0.05" or 1.27mm pitch between pins. 

A basic support makes it easy to use with a standard 0.1" prototype board.



					
										
					
						




					
							

		
	





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An INA219 object is declared and initialised by begin(). 



					
										
					
						



	

    

        
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Acquisition and retrieval are separated.

Acquisition for all values is done by get(), while there are as many functions as measures, with mV(), mA() and mW().



					
										
					
						



	

    

        
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Two Applications




	

		
			

				
					
						


I designed two applications.

The first is a V-A-W-metre displayed on a terminal windows connected through serial/USB to the LaunchPad. Minimum and maximum are monitored for each of the three measures.

The push button selects between V-A-W and mV-mA-mW, resets the minima and maxima, and exits.

This application comes with the library and requires only

Binary sketch size:  6312 bytes (of a 16384 byte maximum)
Estimated SRAM used: 232 bytes



					
										
					
						




					
							

		
	






	

		
			

				
					
						


The second application I've explored uses a 128x64 high-contrast white-on-black OLED screen.

The push button selects between V-A-W and mV-mA-mW, resets the minima and maxima, and changes the decimal separator between point and coma. 

I built two versions: 



					
										
					
						




					
							

		
	













	

		
			

				
					
						




					
								
					
						




					
								
					
						




					
								
					
						




					
							

		
	





The different screens, from left to right: splash screen, measures in mV-mA-mW, measures in V-A-W with point and comma as decimal separator.




	

		
			

				
					
						




					
								
					
						




					
								
					
						




					
								
					
						




					
							

		
	





Selecting the function with the push button, from left to right: ./m. change of units, =0 reset, ., decimal separator, __ cancel.










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