How realistic is running a Xenon from a coin cell?

xenon
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#1

Hi All,

I read somewhere that the Xenon can run from a coin cell as a non-meshing peripheral role. I want to build a simple sensor that reads at 10 minute intervals and transmits a few bytes to the nearest mesh node. The enclosure I want to use has room for the sensor, Xenon board and a CR2450 (540 mAh) cell. Is this design likely to work?

Thanks in advance,

Rob


#2

As the sleep modes have not been entirely implemented yet, it’s a bit difficult to say.

However, to get the lowest possible power consumption using a coin cell battery you’ll need to bypass the voltage regulator. There are trace jumpers that can be cut to do this, however it requires modifying the Xenon. That’s probably fine for a few devices, but might get tedious at scale.


#3

Is there a timescale for the implementation of the sleep mode/s in the Xenon? I have a need to deliver an MVP in the next month.


#4

IMHO that is unrealistic. Before the mesh devices shipped, there were a bunch of people waiting to build products around the mesh devices. Those persons kept pushing particle for a ship date. But as we found out, the firmware had a lot of debugging that needed done and consequently would have been a bad platform to ship in a finished product. Waiting till the last minute to implement a new feature is not wise.


#5

Does anybody have an idea of the lowest supply voltage that will maintain stable operation of the Xenon when using the coin cell as a direct drive ?


#6

The theoretical lower limit is 2.8V. The limiting factor is the QSPI external flash, not the nRF52840. I have not tested this, however.


#7

Another alternative would be to use another BLE sensor (I use one already) with the Xenon in mesh mode or Boron as a BLE master. Does that sound possible? Is the Particle Mesh platform use regular BLE communication?


#8

@rlkeith, do you have room for 2xAA batteries? They are about the same footprint as the Xenon.
Two (L91) AA batteries (direct drive) would give you 3.6V when full, down to 2.7V when depleted.
I’m guessing these will be a decent baseline for battery operated direct-driven Xenons once we have sleep modes, assuming 3.6V isn’t too high.

The L91’s performed great for a Boron in this post (see Trial #2), but using 3xAA and the Boron’s on-board regulator.


#9

How about a 18650 Lithium Ion cell from an old laptop battery? When the xenon is plugged into usb it will even recharge it for you!


#10

Thanks for your reply. I was looking for a compact device that will run on a battery without recharging for a year. The Xenon is not yet up to that stage so I am looking at other solutions.

Rob


#11

Hi Rob,
Your scenario fits so well with what a bluz can do.
If you need cloud connectivity in your device you may look into:

https://bluz.io/
or
https://redbear.cc/product/redbear-duo.html

Both are being phased out (during 2019?) in favor of the Mesh devices.
So once you are up to speed, I’m hopeful that the Xenon will be ready for you. Same tooling, Same cloud.