Minimal design thoughts

[jendrush]

@Ivan-Z Really nice idea for battery powered nodes:)

[korttoma]

@Ivan-Z how did you connect the power to the arduino? How are you powering the Radio? Is it a Pro Mini 3.3V? How long does the battery last? Did you do anything special to the arduino ( hardware changes or something else? )

[Ivan Z]

CR123A in full charge has 4.07v

Gas counter started 2014/11/01.

In winter, temperatures drop below -10

[tbowmo]

@Ivan-Z

You say that it don't need a regulator? the battery voltage is 4.07 when fully charged, that is 0.47V above the absolute maximum rating of the NRF24L01+, as it's only rated to 3.6V maximum. Same goes for the Si7021, maximum supply voltage is 3.6V.

So CR123A is not a good battery, unless you put a regulator in the loop, which then again uses current, and causes a voltage drop from battery supply

[Ivan Z]

DHT22 = 3.3-6V DC

CR123A = 3.6v ( Bat full charge i have 4.07v )

NRF24L01+ = 3.6

I have 8 device and his work with CR123A for 6 months
When charge some device cannot translate packets, but after work

[AWI]

@Ivan-Z I think you are lucky... I burned a few radio's with a similar setup (with LiPO solar charger) I like your minimal design. If you replace the DHT sensor with a htu21 you can make it even smaller. There are a few htu21d boards with a 3.3v regulator on it which you could use to power the radio.

[Ivan Z]

@AWI
What regulator do you use?

I do not use the regulator because it has a extremeconsumption
AMS1117-3.3 = 5~10mV in idle

[AWI]

@Ivan-Z I use the XC6206 series regulator. most of the times. The quiescent current for this one is very low 1-3 uA. This regulator is used by many of the sensor board suppliers to supply sensors with 3.3v Eg. In many cases (eg Adafruit) you can use the board as a "3.3v power supply"

[Roberto Brunialti]

Hi guys. I'm waiting for your board!
the only concern is about the 2xAA batteries adoption that could increase the overall size of a sensor node to a "normal node" size ( http://www.seeedstudio.com/depot/s/devduino.html?search_in_description=0).
I would like a stack as following: battery+board+radio. with the same footprint of the radio module.
The battery could be a CR123 with regulator, and the holder could be a pcb holder as this: http://www.memoryprotectiondevices.com/datasheets/BH-CR2-PC-datasheet.pdf
I actually ordered some of these: http://www.elecrow.com/devduino-sensor-node-v4-atmega-328-p-1201.html, at this moment the closest to my size requirements.
What do you think.?

[AWI]

@Roberto-Brunialti I am looking forward to this board also. I deployed a few Devduino V4's. These are really well built but lack the "minimal" size, have only a few connectors (enough in most cases as a good temp/hum sensor is on board).. And "restrict" you to the use of non-rechargable CR123 cells (3V,no regulator). I will love the very small footprint combined with the flexibility in power sources (and extra features) in the "Minimal design thoughts" design. :heart_eyes:

[tbowmo]

Think we should rename the thread to "Mysensors Micro" as this is the new name, since it's the first "official" board from mysensors.

Anyway, just got a couple of pictures from the factory in China, they have build the first batch of 5 pcb's that they are verifying at the moment, and then they should be shipped to us (either @hek or me?) and then we need to verify it, before giving a go on the production.

So we are comming closer to a "launch" of the device.

[hek]

@tbowmo

Yep, might also be good to create a new thread in Announcement when it has been launched (and is for sale) with a back-reference here for history/design decisions made by you.

I should probably start working on a more complete page on the main site with more details and illustrations.

[Tibus]

In your design, C3, the nrf 4u7 capacitor, is a classic ceramic capacitor. In the mysensors tutorial, they write a polarized capacitor is better for the NRF. I use tantalum capacitor wich are bigger but is there a difference with the ceramic one for the nrf. I would like to use a ceramic 0603 too if there is no difference for nrf.

Thank's

[tbowmo]

@Tibus

In theory ceramic capacitors should be better, it has a lower ESR, and are better suited to reduce ripple, or noise on the supply locally, as it has a faster response to power requirements, than equivalent electrolytic capacitors.

[Mickey]

will it be possible to use this board pcb without soldering the sensor , flash and security chip?

[tbowmo]

@Mickey

Yes, you can use it without those mounted. But I don't think that we are going to sell it without those components mounted

[Roberto Brunialti]

Any good news about the d-day (delivery day :smiley: ) ?

[hek]

Small production run of 200 units started this morning. :)

[Mickey]

@hek said:

Small production run of 200 units started this morning. :)

You would run-out of units very soon...

[Roberto Brunialti]

when preorders will be available ?