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Topic: How can I achieve the 104µA power consumption? (Read 698 times) previous topic - next topic

thomasguenzel

Hey,

I recently bought the MRK WAN 1310, as the WAN 1300 did consume too much power and it seems that the 1300 was not able to shut down the LoRa module (see this discussion on thethingsnetwork.org).

The description in the store states:

Quote
When properly configured, the power consumption is now as low as 104uA!
How can I achieve this? I'm using the LoRa library (without LoRaWAN) and did get the following measurements:

~30mA while idle, but running (no RX/TX)
~9mA with the SAMD21 in deep sleep and using LoRa.end
~0.45mA with the SAMD21 in deep sleep, using LoRa.end and LORA_IRQ_DUMB low, LORA_BOOT0 low, LORA_RESET low

While this is already a huge improvement over the WAN 1300, I'd love to get it down to the 104µA (which would mean the battery would last 3 times longer).
It would be great if someone could tell me some additional steps I can take to further lower the power consumption.

Thanks
Thomas

sslupsky

You need to pay particular attention to the state of the I/O pins to achieve 104uA.  That is, you do not want any of the I/O pins sourcing or sinking current.  Also, you want to ensure none of the I/O pins is left "floating".

BTW, if you use an external power supply, you can achieve a sleep current of about 20uA.

thomasguenzel

So, I finally got time to test it again, with a more precise DMM. I've reduced the code to basically the ArduinoLowPower timed sleep example (although using deepSleep instead of sleep). The whole code is as follows:

Code: [Select]
#include "ArduinoLowPower.h"

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);
  delay(500);
  digitalWrite(LED_BUILTIN, LOW);
  delay(500);
  LowPower.deepSleep(2000);
}


I'm using an external 3.3V power supply, but it still uses 577µA while in deep sleep mode. What am I missing?

sslupsky

When using an external power supply, you need to disable the power supply on the mkr wan.  There is a solder jumper on the output of the mkr wan power supply.  Remove the solder jumper to create an open circuit.  This disconnects the on board supply.  There is significant leakage if you leave the solder jumper in place.

Also, make sure you detach USB.  USB draws significant power when sleeping so you need to shut it down.  In your sketch, add the following to your setup():

USBdevice.detach();


RichardNordkvelde

sslupsky, would this also be the case for the MKR NB 1500? I am trying to lower the power consumption, but I have no luck. Still stuck at ~577uA as Thomas here. I am using a 18650 battery directly connected to the JST battery connection.

Could you please elaborate on the 20uA with external power supply statement? :)

Thanks!

sslupsky

Richard,  Apologies, I haven't been here in a while.  It would be great if this forum had an @mention feature.

The NB 1500 uses the same battery charger IC and linear regulator as the MKR WAN 1310.  I am not aware if it has the jumper to disconnect the power supply though.

I had a quick look at the schematic and confirmed the jumper is not included on the NB 1500.  More concerning though is that the SARA module is powered from the 3.8V supply.  So, I think this means you pretty much have to use the on-board power supply or you would need to do some major surgery on the board.

There is significant quiescent current with the on-board linear regulator that is used after the battery charger IC.  On the order 50uA.  The battery charger also has a fairly significant quiescent current on the order of 35uA.  So, these two components contribute about 85uA to the sleep current.  If you swapped out the linear regulator for one with a lower IQ, you could save close to 50uA.

Your current measurement is quite high.  I haven't done any work with the NB 1500 yet so I cannot provide feedback on the power consumption optimization of this board.  Do you know what the sleep current of the SARA module is?

...

Ok, i checked the datasheet.  The SARA's deep sleep current is 8uA and power off mode is 6uA.  The low power current is about 600uA.  That current level appears to be consistent with what you measured.  So, it could be that the module is not being put into deep sleep.  The good news is that the PWR_ON pin is connected to the SAMD21.  So, it should be possible to put the SARA module into deep sleep or power off modes.

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