Please give me an advice for a simple sensor node

[DenisJ]

Hi there all,
I'm new on the MySensors and also Arduino world so please be pacient.

I just want to make a very simple Temp/Hum node sensor that can be powered
as long is possible from 2 X 1.5V AAA battery.

I decided for ATmega328 + BME280 + RFM69HW.

I have read a lot about battery power sensors and if I understand,
in order to make a 2 X AAA battery sensor, and suck as much juice is possible
from that battery, I'll need a Step up booster module.
But at the doc page is not specified witch one can I use.

I found/read a lot of post that is so old (about 3 to 6 or more years)
..so I want to gentle ask some low-power guru about what type of booster module regulator
I must use at this time please.

Or... maybe someone can give me a link of some similar (fresh) MySensors project that I can study.

Thanks a lot
Denis

[Yveaux]

@DenisJ a step up converter is never 100% efficient, so although you can drain your batteries further, it depends whether you can run your sensor longer with, than without converter.
Furthermore, boosters often introduce noise to the radio supply which can lead to range issues.
As this is your first build, I would simply use 2 fresh aa or aaa batteries to power your node directly.
I have several pro minis with bme280 and nrf24 radio that run for years on 2 aa batteries. Just follow the build instructions for the battery powered node.

[evb]

@DenisJ I'm went the same way as @Yveaux, without booster, see my adventures at https://forum.mysensors.org/topic/11499/checking-mechanical-locked-doors-by-a-battery-based-windows-door-sensor-node
The oldest sensor is now running for 6 months and the battery level is at 89%

Just pay attention at the lowest possible voltage for all your components to operate on a stable way.
If the 328 can go as low as 1.8V, but the temp sensor stops working at 2.2V, then 2.2V will be the lowest voltage that you can go!

[DenisJ]

Thanks a lot all for the help.

So @evb you can confirm me that the internal 1 MHz it's still work on MySensors node ?
I ask this because in this thread (that I take from your link... thanks a lot)
at the first page I read:
"UPDATE 2: There have been reported issues with MySensors 2.x freezing on SlimNodes running at 1MHz, which I've confirmed. Recommended solution when using MyS 2.x, is to use 8MHz (internal) instead."

I'll begin to study the Minicore bootloader first... I have a lot to learn, and here in MySensors forum is a lot of page to read

Thanks a lot again
Denis

[evb]

@DenisJ Yes, I did read also this comment, but wanting to go as low as possible with the batteries voltage, I took my chance and constructed now 3 nodes running on 1MHz internal with MySensors 2.3.2, with the idea, if it don't work, I reprogram with the minicore bootloader, the pro minis at 8 MHz. You don't loose money in trying it out

Today, after 6 months for the oldest node, they are still working without one freezing scenario...
You must just pay attention that the BME280 sensor can work at such low µp frequencies!
Look at the datasheet of this sensor.

[DenisJ]

OK... thanks a lot.
Now I play with an old Arduino Mega and the AVR program in order to write the bootloader

A little question... how can I understand that the BME280 can work at 1MHz please ? ...maybe also the RFM69HC.
Thanks again
Denis

[Yveaux]

@DenisJ I would advise to just build the standard node as described. The 1MHz frequency will hardly increase battery life, if any, but possibly introduces new issues (eg new bootloader).
Your node will be sleeping over 99% of the time, so focus on sleeping current when trying to improve battery life.
Once you feel more familiar with mysensors and Arduino you could try out new improvements, but you can always return to your initial, known good sleeping node.

[DenisJ]

@Yveaux said in Please give me an advice for a simple sensor node:

...so focus on sleeping current when trying to improve battery life.

Yeah you have right... I'll first program the 8Mhz bootloader first.
hen when all will work, I'll study also the 1Mhz one.
My node will sleep, and every minute (aprox 8 sec X 8 watchdog sleeps) will wake up for about 2 seconds.

Thanks a lot again
Denis

[evb]

@Yveaux Correct, the 1Mhz will hardly increase battery life. But the node will continue to work till 1.8V in a safe operating area. I'm referring to your own posted diagrams
https://forum.mysensors.org/topic/10952/battery-pro-mini-1mhz-vs-booster/12

But yes, good advice to stay with the standards, certainly if you are new to MySensor

[DenisJ]

For now I spent all afternoon to program the 328 using an Arduino but I can't
I just buy from Amaz a ISP programmer and tomorow I'll retry.
I'll update the thread.
Thanks all again
Denis

[Yveaux]

@evb said in Please give me an advice for a simple sensor node:

But the node will continue to work till 1.8V in a safe operating area.

Yeah sure, but alkaline batteries are nearly depleted when they get to 1V, so barely worth the hassle.