ADC Pi Plus and battery power monitoring
2280 Views - Created 16/03/2017
You can use the ADC Pi Plus to measure the battery voltage. The inputs on the ADC channels have a voltage divider to convert the 5V input down to 2.048V which is the highest value the ADC chip can measure. To measure higher voltages you just need to add an extra resistor in series with the input which will increase the resistance on the input side of the divider and therefore increase the voltage it can measure.
We have a calculator for using the ADC Pi Plus with higher voltages. You can enter the voltage you want to measure and it will tell you what size resistor you need and the multiplier value you will need when measuring the voltage using our software libraries.
In your case to measure a 5.6V input you will want a maximum input voltage of 6V to give you a bit of overhead. You will need to add a 3.16K resistor in series with the input which will give you a maximum voltage of 6.011V. When you read the voltage from the ADC you will need to multiply the value that is returned by 1.1881 to give you the correct voltage.
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