Measure input voltage

Support Wixel
1

Hi,
my Wixel will run on rechargeable batteries. For this reason I’d like to somehow watch the input voltage. When the input line will be too low, I will do some precautions. The adc library for wixel can measure the 3v3 port and this is, if I get this correctly the output port. How can I correctly wire, to measure the input power level. And what needs to be taken in account, if the circuit is independent of wixel(I suspect the condirion for adc to measure the voltage is that the measured circuit will need to have common ground with wixel)

The small add-on. The internal thermometer is measuring outside(enviromental) temperature or the value is somehow biased with the board thermo radiation? Can I use it to measure “room” temperature?

Thanks for answer

Martin

2

Hello, Martin.

Yes, to get a meaningful result from the ADC you will have to connect the Wixel’s GND to the ground of the circuit that contains the voltage you are measuring. I recommend using a voltage divider to divide the input voltage down to a voltage between 0 and 1.25 V. Then you can use the Wixel’s internal 1.25 V reference to measure it. By using the internal reference instead of VCC, you will get accurate results even when VCC falls below 3.3 V.

The Wixel doesn’t generate much heat, so it will basically be at room temperature all the time, so that is what you are measuring if you read the Wixel’s temperature sensor. We haven’t characterized the effect Wixel-generated heat on the temperature reading but I expect it to be small.

–David