5V power issue with a CubeCellAB01-v2

#1

I have an ultrasonic distance sensor connected to my CubeCell on Vin.
When connected to USB, it’s working fine. Running on 3.7V battery power, however, there is no voltage on the Vin pin, so the sensor is giving no values.
Vdd is giving 3.3V as expected, but not enough to power the sensor obviously, as it runs on 5V.
It does connect to LoRaWAN in battery mode and voltage readout gives around 4000 mV.
Vext is switched off & on when going in/out of deep sleep.
Is this as expected (so no 5V sensors are useable in battery mode) or is there something I’m overseeing?

I’ve thoroughly searched this forum and the internet for info, yet without result so far.

Thanks for any help!

#2

There is no boost circuit on the board so it can’t turn the nominal 3.7V LiPo voltage in to 5V for you.

There are discussions about using third party boost circuits to give 5V on the forum.

You should take care that the data interface is converted to the working 3.3V that the board runs at.

#3

Thanks for the quick reply!
I have a converter board somewhere, so I’ll give that a try.

#4

You might find that the sensor works just fine on 3.3V, despite stating that it requires a 5V supply. I have a couple of applications that use an AJ-SR04M ultrasonic sensor, which claims to require a 5V supply, operating quite happily on 3.3V (Vext) from a CubeCell Plus. I configured a boost converter on the PCB I developed for these applications, but at some point I read somewhere on the 'net that this particular sensor worked fine operating on 3.3V so it didn’t turn out to be required.

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#5

Indeed it runs well on VDD 3.3V power - but only when connected to USB, not on battery mode…
Didn’t get it to work so far. I Might even have blown something when I used a booster… without converting the trigger input voltage :frowning: (Despite @nmcc 's warning…)

#6

Hmmm… Remember that there’s a finite amount of power available from a battery…
P = VI, so if you increase the voltage, you will decrease the available current… If there’s not enough current at 3.3V, there will be even less at 5V, even ignoring the fact that a boost converter won’t be 100% efficient…