[werk_ag]

Currently there are many sellers on eBay that are selling Bosch BMP280 sensors as BME280! They even announce them as BME280. I believe that many of them don't even know the difference... others may be just cheating.
It already happen to me too. Ordered a lot of BME280 and had received BMP280... Obviously I was refunded, but had to wait until a new batch arrived.

AllanG, a member of the WeatherDuino Team discovered an interesting article which may help to identify the right type of chip by looking at the markings on the chips.

Here is the link to the full article: Bosch Sensortec BMP280 vs BME280 Sensor Confusion

[JT118]

The very easy way to check if the sensor is a a "P" or an "E" is to use the test sketches included in the BMP and BME sensor libraries with a spare Nano. Mine were both "E".

 I had come across the article referred to above  but could not read the numbers  even with a magnifying glass. Mine would need a toolmakers microscope to read the tiny numbers.

[uncle_bob]

For once in my life I got lucky then
My sensor is purple and definitely showing humidity correctly.

[AllyCat]

Hi,

Yes, I've also received refunds for purported BMEs. 

One way to tell is that the "can" (i.e. the sensor itself) for the BME is almost square (2.5mm) whilst the BMP is more rectangular.  But I think they both fit on the same PCB footprint, so the boards are marked with both BMP and BME legends and at least some of the "confusion" is genuine mistakes.  Often the descriptions are "misleading" for the same reason as if I were doing a cut-and-paste in Chinese.  

My advice (unless you want to receive a "free" BMP280 ) is to avoid the "6-pin" modules (daughter boards), and of course any that are priced below about 2 UKPounds/Euros/Dollars.  I recommend the (rather smaller) "4-pin" modules, often sold as "5 volt" compatible, which have a pair of buffer (level changer) FETs on the back of the board.  Sometimes the sellers don't show the rear view, but the style usually can be determined from the top view.   When I was looking, the lowest price from China was almost $4, or more than £10 for the "branded" versions from Europe.

Cheers,  Alan.

[werk_ag]

  I recommend the (rather smaller) "4-pin" modules, often sold as "5 volt" compatible, which have a pair of buffer (level changer) FETs on the back of the board.  Sometimes the sellers don't show the rear view, but the style usually can be determined from the top view.  

Hi Aan,

I also prefer those versions, and I still have some. The problem is that currently I can't find them on sale anywhere.
Do you know of any source where I can buy them?

Those versions have an special advantage for the WeatherDuino users. Due to the par of FETs included, they can be connected directly to extended I2C bus port on the TX boards, while the more recent versions can't (at least without using another bus extender chip on the sensor end)

[AllyCat]

Hi,

I haven't bought any for about a year, but they still seem to be available, at least on the "UK" site ("locally" at a higher price, or from China), for example :

https://www.ebay.co.uk/itm/BME280-Digita...0505.m3226

I'm a little concerned that the 4-pin breakouts are also now marked BMP/BME, so "mistakes" might happen.  Price should be an indicator (don't expect a BME for 99p or £0.99) but perhaps the safest solution is to buy from a seller who is offering both types.  For example I quickly found the following where it looks as if the best price is now a little under £3 :

https://www.ebay.co.uk/itm/10DOF-I2C-SPI...:rk:9:pf:0

https://www.ebay.co.uk/itm/MPU9250-BMP28...rk:30:pf:0

I recognise all the above as quite "established" ebay sellers (so hopefully reliable) and probably there are others such as "alice".

Cheers,  Alan.

[AllyCat]

Those versions have an special advantage for the WeatherDuino users. Due to the par of FETs included, they can be connected directly to extended I2C bus port on the TX boards, while the more recent versions can't (at least without using another bus extender chip on the sensor end).

Going slightly Off-Topic.  I believe the same applies to the VEML6075 (UV) sensor (i.e. 3.6v max rating).  I'm particularly interested in using (or testing) that device because I believe it offers the best possibility of obtaining a "real" UV Index value (which is heavily weighted towards the UVB end of the spectrum), because it has separate UVA and UVB channels.  Also, it has two more channels weighted towards the Visible and Infra Red parts of the spectrum, so I wonder if it can also provide the "normal" Solar Watts/m2 value.  That gives the possibility of doing all the Solar measurements via a single (extended) I2C bus and a tiny optical "window".  But of course it would require a "special" Arduino Library, which I'm certainly not competent to devise (yet).

So your comment got me thinking (and searching) and I found the following; several Pounds more expensive than the normal 3.6 volt VEML 6075 breakouts (like the one I already have), but perhaps an "easy" solution. 

https://www.ebay.co.uk/itm/VEML6075-UV-A...:rk:9:pf:0

Cheers,  Alan

[werk_ag]

Hello Alan,

Thanks for the links for the 4pins BME280.
Do you know of any source for the SHT31 sensor modules that also have the two FET's?
Some time ago (a year or so) they were comum, but now I only find modules without the buffer.

So your comment got me thinking (and searching) and I found the following; several Pounds more expensive than the normal 3.6 volt VEML 6075 breakouts (like the one I already have), but perhaps an "easy" solution. 

https://www.ebay.co.uk/itm/VEML6075-UV-A...:rk:9:pf:0

Cheers,  Alan

That one is exactly the model I used some time ago, when I added support for the VEML6075 sensor on the WeaterDuino system.
Currently it isn't installed, as I'm still trying to find a good enclosure for it.

[AllyCat]

Hi,

I found a 10-pin VEML6075 breakout for only US$5.25 , so now I will just have to be patient (and keep my fingers crossed).

AFAIK the SHT3x humidity sensors are 2.4 - 5.5 volts tolerant so shouldn't need any level shifter? 

On a related topic, RS Components (still known as "RadioSpares" by some people) sell the Sensirion filter caps for only around £1 / Euro each (depending on quantity).  They're mainly intended for the SHT2x (and a suitably designed PCB) but it's not too difficult to cut off or modify their "pegs" and fit to the cheap Chinese breakout boards.  I've not discovered which glues are "safe" (or not) to use near these humidity sensors, but the filters might extend their life, particularly outdoors.  :

https://uk.rs-online.com/web/c/?searchTe...ra=oss&r=t

Cheers,  Alan.

[41south]

I bought these VEML6075 break-out boards

https://www.tindie.com/products/blkbox/v...r-arduino/