Read overall current drawn on PoE MicroMod Ethernet Function Board

Development Boards MicroMod
1

Hi,

is there a way to measure the overall current drawn by the PoE Micromod Ethernet Function Board from the PoE connection to power everything that is attached to the Micromod mainboard and its connected Qwiic devices, all powered by PoE function board?

I’ve read in the hookup guide that there is a solder jumper called MEAS that:
“Open to measure current drawn by the Function Board.”

Will I be able to read the overall current drawn or just the current drawn by the function board itself? (no processor, no Qwiic, no Amplifier etc.)

2

Cut either PW+ or PW- and measure current across those pads. That gives you current for everything.

3

Hi, sorry but I do not understand what exactly I should cut.

You are not talking about the MEAS solder jumper, right?

So which one do you mean? - Looking at the schematic

4

They are labeled “PoE Power” in the picture you attached. The schematic
has them labeled “ISO1” and “ISO2”
Just cut one of them and measure across the cut.

1 Like
5

Thank you @YellowDog I will try that asap.

6

OK readout works but confuses me:

I get around 700 - 900 mA (depending on if the audio amp/speaker makes a sound or not) for:

  • 6 Qwiic devices (Button, Haptic, RFID reader, IMU, OLED Display, Wav Trigger)
  • The Micromod single board + Teensy CPU
  • PoE Ethernet function board
  • Speaker 8 Ohm 2,5W + Qwiic Amplifier (powered separately via the Micromod VBAT/GND 4,2V)

The system runs stable, but:

  • according to product website , the PoE DC/DC converter supplies 9W @ 5v (if I am correct P=UI so 9W=5V1,8A)
  • converted to 3,3V this would mean 9W= 3,3V*2,7A right? (but Ampere would be capped at 1,8A anyways I assume? So with 3,3V there would be aroudn 6W total available?)

So does that mean that I could theoretically add Qwiic devices up to a total power consumption of 1800 mA where I stand at 900 mA at the moment ? In e.g. the amp hookup guide it says to add an external power supply even for the amp alone to not make other Qwiic devices struggle, but I would be far away from the max limit, or?

7

You can test this experimentally to find out quickly