Measuring Qt Py power usage

[mariosangiorgio]

Hello, I’d like to replicate https://learn.adafruit.com/adafruit-qt- ... ower-usage with my Qt Py and sensors with the goal of understanding how much battery life I would get.

https://learn.adafruit.com/adafruit-qt- ... rd/pinouts says:

You can also use the 5V pin as a voltage input but you must have some sort of diode (schottky, signal, power, really anything) between your external power source and this pin with anode to battery, cathode to 5V pin. There are two pads on the back, with the protection diode in series, so you could use those if you wish.

I have a few diodes 1N4001 and 1N4148. Would any of these work?

Alternatively, if I wanted to use the BAT/GND pads, is there a way to connect to them that doesn’t involve soldering? I don’t want to solder them just for a test. If all goes well I will be using a BFF LiPo charger in my final project.

[mikeysklar]

Your diodes are fine to use.

Do you have a Nordic nRF-PPK2 which was used for those power tests?

https://www.adafruit.com/product/5048

Maybe it would make sense to monitor through the USB so you can avoid the soldering or purchasing a power profiler.

https://www.adafruit.com/product/2690

[mariosangiorgio]

Thank you! I was reading more about diodes at https://learn.sparkfun.com/tutorials/diodes/all, which says “1N4148 has got a typical forward voltage drop of 0.72V and a 300mA maximum forward current rating”. Are things going to break if the board draws more than 300mA? According to the data sheet of ESP32-C3 peak consumption with WiFi could get up to 335mA.

The same page says “The 1N4001 has a current rating of 1A and a forward voltage of 1.1V”, would that be a better choice?

For reference, I looked at the schematics of the QtPy and I see it uses a NSR0320 which a quick search tells me is “ 1.0 A, 20 V, Schottky Barrier Diode, Low Forward Voltage”

I don’t actually own a power profiler. I was looking at it because I hope my power consumption would be lower than 1mA so outside the range of the USB voltage meter. Thanks for the recommendation though, at this stage I am absolutely a beginner and the Nordic Power Profiler Kit is totally overkill. It does look really powerful and cool though :)

[mikeysklar]

The 1N4001 would be a good choice. Our page lists them with 0.7V voltage drop.

https://www.adafruit.com/product/755