Which microcontroller for Node

[gohan]

I got sht31 sensor and it seems very good but it's a little expensive

[LastSamurai]

@Tommas said in Which microcontroller for Node:

Hi @LastSamurai

Thank you!

Which mini pro do you suggest? The 5V version?
What about the nano? It is about the same price as mini pro.

Have you got reliable buying source?

Thank you!
T

Thats really up to you and what sensors you want to use. My nodes are nearly all battery powered so I use 3.3V pro minis as these can be most efficient. Pro minis are a little cheaper most of the time but the nano has build in usb which makes it a little easier to work with. Use what you like more. They both use the same atmega328p so there is really no difference.
I just buy most of my stuff from aliexpress. Just find the cheapest search result from a seller that has many positive reviews. Has worked 99% of the time for me.

ESP8266 (something like nodeMCU) could be an easy alternative too if you have powerlines already. I still like the idea of not relying on wlan though (and using the nrf24l01).

[d00616]

@Tommas If a 3.3V only controller is OK for you, then look at the nRF52832 MCU: https://aliexpress.com/item/nRF52832-2-4GHz-Wireless-rf-Module-CDSENET-E73-2G4M04S-SPI-SMD-rf-Receiver-transmitter-Bluetooth-Module/32819293925.html

The nRF51822 or nRF52832 MCU is supported with the upcomming MySensors 2.2 release. The radio is compatible with the nRF24 with better range in most cases. BLE is not supported with MySensors.

At the moment OTA update is not implemented.

Layouting your PCBs is a little bit simpler. Most included hardware like UART, SPI, I2C can be assigned in Software to pins you need. To manage the pin layout in your sketch, you have to follow the ArduinoBoards instructions and install the "My nRF5 Boards" boards.

Look at:

• https://www.openhardware.io/view/376/MySensors-NRF5-Platform

[Tommas]

Hi @LastSamurai

If i powered a 3.3V mini pro from 2 AA (2000mAh) battery, how long my sensor node can work? Approximately..? NRF24L01 low power, MQ2, si7021, lm393 light, PIR motion, one relay module, and a sound sensor? Or these are too much for battery power?
Can I attach these directly to the mini pro power output?

Thanks,
T.

[gohan]

Since you are going to use as relay, don't you already have a power source nearby?

[Tommas]

@gohan

Dear gohan.

Sorry! I think about a general solution. We can forget the relay for now. I would like to know where is the limit approximatelly if i used battery with not too complocated circuits...

Best regards
T

[gohan]

The problem is how often you want reports of the sensors and if you can power them down.

[mfalkvidd]

@Tommas a "generic" solution would get a battery life anywhere between a few hours to about ten years. There are a lot of parameters involved. https://www.mysensors.org/build/battery documents the most common parameters.

[Tommas]

Dear @mfalkvidd

I think that i will use mini pro 3.3V version and in this case it is i will be capable to run it from battery or external power source.

Thanks
T

[Nca78]

@Tommas said in Which microcontroller for Node:

Hi @LastSamurai

If i powered a 3.3V mini pro from 2 AA (2000mAh) battery, how long my sensor node can work? Approximately..? NRF24L01 low power, MQ2, si7021, lm393 light, PIR motion, one relay module, and a sound sensor? Or these are too much for battery power?
Can I attach these directly to the mini pro power output?

Thanks,
T.

Hello, MQx sensors are not ok for battery powered sensor, they use too much power.
It's the case also with sound sensors, it can work for a reasonnable time (over 6 months) with 2xAA because they have a lot of energy, but it's not really suitable for battery power imho, microphones use around 200uA.
Relay can be ok if you use a bistable relay = using energy only when switching state. Classic relay will use too much energy to stay connected.

PIR sensors (not all but a few) can run for a long time on battery, si7021 will just have an "endless" battery life on 2 AA, light sensors like OPT3001 or SI44009 can also have extremely long battery life.

For the power issue to make things simple I would suggest using 3.3V devices, and power with 5V:

• losses in voltage from long wires will still allow your devices to run from voltage regulators
• if you power from 12V and go for cheap arduino clones (pro minis or nanos) the voltage regulators will not be able to cope with the voltage (most of them don't like over 9V)

[Tommas]

Dear @Nca78

Thank you for the long answer.
Could you suggest power module (in 5V ---> out 3.3V and 5V? I think something like with integrated microusb plug) what i can to build in to my circuit?

Best regards
T

[Nca78]

@Tommas if you use 3.3V pro mini you can just connect to the RAW and GND pins and the onboard regulator will do the job.

[Tommas]

@Nca78

Another question.
Can i use the mini pro's 3.3V output for all of my 3.3V sensors? Cant i exceed the current limit of the mini pro with these sensors?

[mfalkvidd]

@Tommas yes you can. Compare the value in the Pro Mini's datasheet with the numbers in the datasheets for your sensors.