Which microcontroller for Node

[Tommas]

Dear All!

I would like to place sensor nodes to all of my rooms.
I plan, that i will power these from a central power source (12V or 5V).
The distance between a node and the power source will be max 20m.
I would like to ask your opinion about:

• which microcontroller do you suggest? (arduino nano, mini, sensebender micro) sensors will be: 1-2 relay, gas sensor, temp+hum, light, sound, motion
• should I power with 12V or the 5V is enough?
• Where do you buy low cost enclosure (something with nice design)?

Thank you in advance!

Best regards,
T.

[LastSamurai]

Can't help you with all of it but:

• I guess the cheapest one: arduino pro mini. You don't need the usb from the mini if you have a programmer and the sensebender micros' energy saving features aren't needed if you power them directly. Having many sensors you could save some money this way
• I don't know about losses in the cables and stuff like that but beside powering leds/motors/... from the same source 5V is more than enough. Most sensors actually run fine with 3.3V
• Nice design is very subjective but ebay and asian stores like aliexpress have many many plastic and metal cases. Just browse a little until you find something you like.

Hope this helps a little

[Tommas]

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

[gohan]

I'd consider also the esp8266 or newer esp32 if you are going to have the nodes powered and use your wifi. It is going to simpler as you don't need to attach the radio module.
For the enclosures look in the shop area of the mysensors site.

[Tommas]

@gohan

Dear gohan!

Does This mean that every node has an IP address and communicate with the gateway over my WiFi network?
Thanks
T

[gohan]

exactly and you could also get wifi OTA if you want. Of course your wifi needs to be on for them to work while if you go with the classic radio modules you are more independent from wifi but you still need a gateway. If you are fine with wifi you can save some money just buying the esp8266 modules instead of arduino + radio.

[Tommas]

@gohan

It sounds very good, but i have started to use nrf24 with arduino and sensebender stuffs so i would like to continue with these ... but thank you for the suggestions because in the future i will test the esp solution.

I havent decided yet which arduino i use... the sensebender micro is very good because it has good quality humidity ad temp sensor integrated on it, but it is a bit expensive... arduinpro mini with the same temp sensor is max 6-7USD

[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.