And how this solves our problem with BME280 beeing unavailable globally?
They have 7816 pcs more )))
But yes, the issue with BME280 shortage is quite painful. This sensor gives 3 important parameters.
Temperature can be used to distinguish internal sensors from outdoor. Also can be used to predict dew point and else.
Humidity is important in context of PM measurements using SDS011 or similar sensors. If humidity is over 70% then SDS011 sensor became “blind”.
Pressure can be used to estimate the level of installation which is also important for PM values evaluation.
Using 2 sensors is not the best solution as this is more difficult to assemble to sensors. Well, unless they will not be soldered on a single PCB…
I was thinking about two sensors on one PCB.
Why do you think that only after 70%?
And what mean “blind”? What type and value of error?
70% from datasheet is value of environment to electronics not breaks.
I don’t think so.
Let’s focus on resolving problem.
BME280 and BMP280 are officially not available. Maybe they will be in stock in July. Right now we need to make a decision to switch to other available sensor or manufacture own module.
It’s crucial to have at least temperature and relative humidity. If we are going to use only T and RH, we could use standard SHT30 or SHT31 module from China. Cheap and easy solution.
But if we are going to manufacture own modules IMO the best two sensors are:
- Sensirion SHT30-DIS-F
- Sensirion SHT31-DIS-F
They are available. Well designed and reliable. Support for those sensors is already implemented in the firmware. PTFE membrane protects sensor mirror from dust so it is a bit better suitable for outdoor use. Price difference between SHT30 and SHT31 is not so huge. I would go with SHT31-DIS-F.
Finding available good barometric pressure sensor might be hard this days. STM LPS22HH might be a good candidate but current firmware doesn’t support this sensor.
DHT22 (AM2302) is another option. TBH I hate this sensor. OneWire has a very tight timing constraints during communication. Also capacitance mirror in AM2302 easily accumulate dust and moisture - and than shows 100% RH all the time.
Might be useful:
Another supplier. The price there is 2.5 USD but you need to order via diller…
https://m.tb.cn/h.4nTgkfM?sm=acd5d2
Because BME280 is mostly unavailable, and when it is, it comes with astronomical price we will switch Kits from Nettigo to SHT31 modules.
Compared to BME280 we will loose atmospheric pressure, but we will gain a very precise relative humidity and temperature. As some of you might know, precise measurement of relative humidity is crucial for good software compensation algorithms.
If you think it’s a bad idea - now it’s a good time to speak up. BME280 will be available probably in 2021Q4 / 2022Q1.
@irukard How about the SHT40? It also has the IP67-compliant filter membrane like the SHT3x-DIS-F, but at about half the price?
I don’t think Sensor Community firmware supports this sensor.
Hi Irukard, Hi everyone. I’m Gabriel, from France.
I am considering the same substitution as you : sht3x for BME280.
Before doing that, I’d prefer to know more about its suitability to the project.
I found some “literature” on the subject : Compare DHT22, AM2302, SHT31, SHT71, Si7021, BME280.
Compare DHT22, AM2302, AM2320, AM2321, SHT71, HTU21D, Si7021, BME280
which sounds very reasuring… but it is just one source with substantial data.
Other sources I found are ref to this one, or just hearsay (which still can be of some interest, but not as reliable).
Do you know other good sources for datas? what is your conclusion/observations on the matter after 3 months on the subject ?
Pierre Jean Gueno told me you were the Goto Guy on this 
From my perspective BME280 has the best price to cost ratio. However SHT31 and SHT35 are better in measuring both temperature and relative humidity. Also SHT3x-DIS-F option with PTFE membrane on top of sensor is great for outdoor usage.
In my lab I use two pairs of BMP390L and SHT35 as reference point in test chamber. This is very nice combo, especially with PT1000. Most of original BME280’s were in specs (±0.5°C). Occasionally I saw poorly calibrated units with ±0.7°C. All of them behave in similar fashion following the reference point.
The source you are referring was first published in April 2016, and was updated multiple times since than. It shows many neat charts but you have to acknowledge that Robert (the author) used only one orf two sensor types for each test. Instead of using 5-10 sensors of any given model from different manufacturing batches and purchased from different sources. This is a very nice overview but as data source it isn’t something I would like to rely on.
You also have to acknowledge that for popular sensors there are plenty of counterfeit units on the market, eg: DS18B20, BMP280, AM2301, etc.
Sometimes you are able to spot counterfeits visually, other time by analyzing response times, contents of registers, etc. In case of DS18B20, the great work was done by Chris Petrich (currently working at SINTEF Narvik, previously at Sea Ice Group at the Geophysical Institute at UAF). GitHub - cpetrich/counterfeit_DS18B20: How to tell original from fake DS18B20 temperature sensors. - this example shows how crucial is developing tools for identification of genuine sensors especially in global shortage times.
This is also why I was thinking about manufacturing our own modules from parts ordered directly from manufactures and authorized resellers. We all here because of Citizen Science. I hope this doesn’t turn into Citizen Bullshit Data Source.
Long story short - Yes, I believe that SHT31 is a good sensor 
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Thanks for your precise answer.
You seem to imply that sht31 may not be a good choice for outdoor measurements, Am I correct ?
You also say you are thinking about making your own (I guess you mean a board with the sensors from a verified supplier). Have you made steps toward this goal ?
(PCBA design, quotation from PCBA supplier…)
I’d be interested in this dev.
integration of DS18B20 seems far from what is usually made for sc sensors, in my opinion.
SHT35 seems really expensive, even in high quantity (mouser : 3.74€ for a thousand).
SHT31-DIS-F2.5kS is a PTFE protected version of SHT31, right ?
Its price for orders of 1000 is 1.79€. With board and assemby, it could mean 3-4€ for a sensor, which is quite acceptable.
On my side, I’d need 500 sensors. If we go at it as a group, ordering 1000 (or even more) seems reachable. What do you think ?
The question is, does this worth it (PCBA design can be time consuming) if BME280 comes back to its usual price in july…
Standard SHT31 like many similar sensors have capacitive mirror visible from outside. There is a possibility that dust particles will land on this mirror making measurements inaccurate.
Yes. I made prototypes for NAM 0.3.
Now I got version 1.2 and working on 1.3.
RHTP-10 / RHTP-11 is based on SHT31+BMP388
RHTP-20 / RHTP-21 is based on SHT35+BMP390L
RHTP-x0 have 0x45 + 0x77 I²C addresses
RHTP-x1 have 0x44 + 0x76 I²C addresses
Sensor have connector compatible with SparkFun Qwiic & Adafruit STEMMA QT.
But this sensor will have to wait since BMP388 is also unavailable right now.
For me typical use case for DS18B20 is as soil/water temperature sensor.
Yes. All DIS-F sensors have PTFE cover.
That’s why I simply designed better sensor, with:
- SHT31 and BMP388 for good price/accuracy ratio
- cheap enclosure with M16 thread
- modular, low profile connector
- thermal shield and thermal gap between inside of MCU enclosure and outside environment
- low dead volume, yet with good rain/snow protection
I’m also experimenting with conformal coating for harsh environments. I would like to build very robust and affordable sensor. Which is easy to mount to every device with M16 thread or 16mm hole. Sensor designed with Citizen Science in mind, not just another module for Arduino.
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@irukard
Any progress on the prototype?
By the way, is the DHT31 sensor shipping with Nettigo kits of the DIS-F variant?
Dear all, thanks for this thread !
Any update on a low-cost sensor which I could use instead of BME 280 ?
Right now I am stuck and I do not want to use a DHT22 
Thanks
Marie-Laure
Nettigo is selling the SHT31 as an alternative for the BME280. But the SHT31 doesn’t measure air pressure.
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How about AHT10 and AHT25 sensors?
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I like the idea for the sensor and the cheap cap, but shouldn’t the hole of the cap be protected with a grid/net?
Wild bees love such holes with cavities and use them for their brood and then close these holes.
https://forum.sensor.community/uploads/default/original/1X/ae5ae44911d7cf1dd02847cd60b7e8f2ec7d9b3f.jpeg
Wild bees (depending on your location) like Megachilidae require tunnels that are several centimeters deep. To me this setup seems to be to shallow. Nevertheless there may be other invertebrates that like to use the setup as a (temporary) home, so covering with some kind of mesh seems to be a good idea. To be totally safe the grid size needs to be fairly small (1x1 mm).