Current measurement of Microchip RN2483 LoRa Technology Mote


(Osman) #1

Hello, Everyone

Has any one tried to measure current for the Microchip RN2483 LoRa Technology Mote using an oscilloscope? I am using the simple setup with 10ohms resistance in series with the supply and connecting the probes across the resistance. The results are strange.

Does any one know any other measurement technique apart from DMM.

I was expecting the waveform like this as below:

Reference http://ztrackmap.com/2017/03/16/can-determine-battery-lifetime-lorawan-devices/
But this was done using RN2483 module and not the Semtech LoRa Technology Mote.

Is it due to some step up converter being used in the mote that i am getting pulses ?
Please anyone could look in to this matter.


#2

without knowing the mote exactly, I assume that there is strong influence of capacitors letting the voltage trop slower than measuring with the “naked” RN2483


(Osman) #3

The waveform that i posted is for idle state of loRa mote. Its really confusing what is happening to the waveform as the mote is not processing anything.


#4

That’s interesting, I also did that Mote measurement straight on the RN2483 to see if I get a similar signal.

Looks almost the same


(Osman) #5

Thanks for your reply. So, were you able to compute current consumption for the RN2483 mote?
If you could guide me how to puruse for the current measurement for this loRa mote it would be great. I am thinking to buy a current sensor and put that in series with my mote. The current sensor being interfaced with arduino board would give me current readings.

Is this the right way ? Do you have anyother idea?

Thanks once again :slight_smile:


(Osman) #7

Could you kindly explain your measurement setup. Where is the other terminal of resistor being connected ?


#9

Let me try to explain, if I do get it wrong, I’m sure someone can correct this :wink:

Assuming you do the measurements on a Microchip LoRa Mote instead of a Semtech LoRa Technology Mote, you can indeed get a similar signal when you measure directly on the RN2483.

The result of your measurement is explained when you look at the schematic. The Mosfett Q1 and Schottky diode D1 are a typical polarity protection. Then there is the capacitor C3, followed by the step-up converter MCP1625T. I think your resistor is in serie with that capacitor C3 and It seems like you’re measuring loading/unloading C3.

What I measure is the voltage over of a resistance during one transmission action, but of course it is not measuring LoRa Mote’s power consumption. Yes, you know the resistors value, read the voltage and time of that transmission action from the scope and do the calculations for this transmission but that’s not the total powerconsumption of the LoRa Mote, besides there are several other factors that we need to keep in mind.

If you look at the schematic again you can find some spots for direct measure on the RN2483. You can put (like GPIO connector J4) a 10 Ohm resistor in series with one of the 3.3V connection and your powersupply. Connect you probe over that resistor. Keep in mind there is a voltage drop over that resistor so the your input voltage at the RN2483 is slightly lower than the source.
Set the correct timebase, vertical division, vertical offset, the trigger point and take a single trigger shot. With the scope cursor you can do further measurements.

If you configure the Mote for different data rates you can see the difference in the graphs.

Data rate 5SF7

Data rate 2/SF10

Data rate 0/SF12


(Osman) #10

I am so thankful to you for your explanation. Surely, i will try this on Monday and will upload the results. Just one last thing, I have to power up using 3.3V and GND pins on RN2483 moule (a resistor in series with 3.3V pin).

Thanks a lot once again !


#11

Yes sure, take a look at my very first photo. I’m using a external power supply, ground is connected to the metal of usb connector. Power button on Mote is ON (but there are no battery’s in the Mote). That big red crocodile is the power supply’s positive.


(Osman) #12

I am really thankful to you sir. I got the results after following the steps. Lucky to have people around us who like to share and help others.

Thanks best regards


(Curry) #13

I’ve been using this one a lot, www.qoitech.com for other components, not the RN specifically. Works great to get real good insight in the current consumption and battery life. Really easy to use.