The WORKBENCH part 1

(Bsiege) #995

I have BMP180, BME280, HTU21D and SHT31 since longtime inside a Davis shield. I can say, that the Bosch sensors are surprisingly different in measuring. HTU21D and SHT31 are nearly identical. There are no other electronics than the sensors inside the Shield. What all sensors have in common: They react quite identical on changes. What also can be a problem: errors in the used arduino libraries. I prefer I2C on this sensors to omit some calculation errors. davis2
Here you see, that the difference between the two Bosch Sensors is around 1° I think they are designed for mobile phones, where you cannot expect exact weather measurements.


Bosch sensors tend to go very quickly to 100% humidity imho


(Mat89) #997

Yes, the BME280 is not made for temperature measurement (as also stated in the datasheet), for temperature I use the easy to use and easy to place DS18B20 so far. That humidity goes fast to 100% is a real pain yes @BoRRoZ. Maybe I will change it one day…

At least I need temperature, humidity and pressure, and I would like to not interact with too much different sensors…
Maybe this one would be a nice candidate to test, maybe someone has already used it?

It is a small breakout wich holds a Si7021 and BMP280.


there is also is lesser discussed aspect of those cheap I2C sensors… some of them don’t have a ‘real’ I2c bus.
the manufactures do that to avoid license fees.

sure they work with the available libraries, a problem can occure when you put the mcu in deepsleep and then wake up, for example the older sensirion (SHT) sensors had that 'problem

@mat89 did you buy that davis shield online in the ELV shop ? … I can’t find it ( need more coffee)

this tindie UK shop is specialised in sensors (and very helpfull to)


edge connectors- for outdoors use the longer ones So you can mount an O-ring

(Mat89) #1000

sorry @BoRRoZ, I’ve missunderstand your question, you mean where I got my Davis shield from, not the cheap shields :smiley:.
I got it from Switzerland from this shop:

OK, thank you for the input about the SHT sensors and also the link to tindie. Maybe I should simply try the one from ali and test if it does work or not.


I am testing the SHT-31D with filter - looks promising

(Deux Vis) #1002

Indeed, but I don’t regret it as after a first session of use I really appreciate it.

Associated with a pico projector, nice for group work.


and I’m still waiting… :roll_eyes: … looks great and good to hear that your happy with it.
did you bought that one lens to increase the workspace separate ?

(Deux Vis) #1004

Yes I bought it. It is a little bit too effective, I have to set the base of the gantry all the way to the top of the steel tube to get a focusable view.
But it actually leave a lot of room for soldering which is good.

If something like a x0.75 one exists it would probably be enough.


Also see:


DIY StevensonScreen made from 'upside down plastic bowls



absoluyely nottoscale model LoRa tracker antenna BoRRoZ™

basically its a 50% rotating reflector around a stationairy 3 dbi antenna
the reflector only comes out when the signal is getting weaker, direction is controlled by gps
real tube dia = ca 34 cm … not tested yet but found the parts so I’m gonna build it… someday :roll_eyes:

theoretically it could work



FRAM … connecting it was the easy part :sunglasses:


I’ve asked the manufacturer for more info … can it be 'hacked for EU use ? ( $88.69)

update : I translated the chinese datasheet and basically they have 2 types, wifi / gsm both connect to a private network… lorawan A,C @ 433mhz , my guess… forget it
for further info : Shenzhen Moron Technology Co., Ltd



when storing sensordata in FRAM you need to timestamp it … so an onboard RTC.
there are these DS3231 mini pcb’s… if you remove the header they are pretty small.

mini RTC DS3231

test I2c bus again


set the RTC time with help from the excellent J.Christensen library



elabo … nice :sunglasses:

(Remko) #1012

A lot of construcion work done this sunday afternoon: 2 gateways! one IMST and one RK831. now lets look for a nice housing.


#1013 :wink:

(Remko) #1014

Please no PVC thats no good for RF. Sorry. :tired_face: