Adafruit’s INA219 FeatherWing puts power-monitoring problems in the past. Instead of struggling with two multimeters, the INA219 chip can be used on the breakout to measure both the high side voltage and DC current draw over an I2C with 1% precision.
The chip works with any and all Feathers from Adafruit. Since it communicates over I2C it is extremely simple to use, and the I2C address is configurable to have up to four of these Wings on one Feather.
Due to the severe chip shortage, Adafruit updated the design to work with INA219A or INA219B and in SOT-23 or SOIC package. These changes were brought on by whatever type of chip was available on the market at the time. The A version is a ∓1% total max current measurement error over the entire ∓0.5% max at 25°C range and the B version is ∓0.5% total max current error over the entire temperature range ∓0.3% max at 25°C. The overall functionality of the system otherwise remains the same.
Many current-measuring devices are focused on low-side measurement. That means unless a battery is used the measurement resistor must be placed between the target ground and the true ground. The problems in the circuits arise since electronics tend to not like when ground references change and move with a varying current draw.
The INA219 is a smarter choice. It can handle a high-side current measuring up to ∓26VDC, even though it is powered with 3.3V. The chip will report back the high side voltage, which is an advantage to tracking battery life or solar panels.
A precision amplifier measures the voltage across 0.1ohm, 1% sense resistor. The amplifier’s maximum input difference is ∓320mV. This means it can measure up to ∓3.2 Amps. With an internal 12 bit ADC, the resolution at ∓3.2 A range is 0.8mA. With the internal gain set at the minimum of div-8, the max current is ∓400mA and the resolution is 0.1mA.
Advanced hacks include removing the 0.1 ohm sense resistor and replacing it with another to change the range. Suggestions for changes include 0.01 ohm to measure up to 32Amps with a resolution of 8mA.
Find further information on the Adafruit INA219 FeatherWing on the product page.
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