I want to measure the current power consumption of the Sodaq Ndogo (the microprocessor).
I’ve did this before with an Arduino Uno where I was able to pull the processor out of the board. Since this isn’t possible with the Ndogo (and a lack of knowledge in physics) I dont know how to measure this.
Can anyone help me out?
Hi Gerard,
It would quite difficult to measure the current on just the main processor. The specific chip package used makes this quite difficult and attempting it would likely cause damage to the board.
However, you can measure the power consumption of the whole board by powering it from a battery and running the battery connection through an ammeter.
I connected the 3.3v output from the Arduino Uno to the Ndogo 3.3 vbat and then I connected the ground of the Uno to the Ndogo ground. (Ndogo is running now)
Then I placed this multimeter in between the uno 3.3v output and the vbat of the ndogo.
I put the settings of the multimeter like this picture, but it keeps saying 0 (no measure) and the Ndogo stays off.
If I understand it correctly, the 3.3V output from the UNO is connected to mA terminal and the COM terminal is connected to the VBATT pin on the Ndogo. The meter is wired in series and there is no parallel direct connection between the 3.3V supply and the VBATT pin?
Assuming that it is wired in series, that is the correct setup. I believe the issue is to do with the voltage you are supplying to the Ndogo. The LiPo battery will supply between 4.2-3.5V depending on its level of charge. The onboard regulator ensures that the chip is supplied with 3.3V.
You mention that the Ndogo runs when you wire it directly to the 3.3V supply, but it fails to run when the meter has been placed in series. This may be due to the burden voltage of the meter dropping the output below some threshold. The direct 3.3V supply may be very close to that threshold already.
I would be curious to see what the voltage reading is after the meter. Also you could try using a LiPo battery as the source (supply about 4.2V if fully charged).
Exactly.
I have a LiPo battery with a JST-PH plug.
Is it safe to plug two jumper cable in it and connect it to the vbat & ground?
Or can I connect it to the arduino’s 5V ?
According to the Ndogo datasheet the regulator is a SPX3819 which can operate with up to 16V. The same regulator is used to power the board when the USB is connected (it switches off the battery supply in this case).
So a 5V supply is fine.
I normally use jumper cables inserted into the JST connector on the battery. When adding extra wiring to the battery you need to be careful not to create a short. Also the JST connector gets a bit looser after.
For accurate current measurement, I would recommend have a look at this tool:
