Author Topic: Experience with DIY sensors - BME280, etc?  (Read 1747 times)

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Offline chbla

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Experience with DIY sensors - BME280, etc?
« on: March 07, 2017, 02:19:17 PM »
Hi there,

I'm currently re-creating my DIY weather station. It is arduino based and connected
to my smarthome via arduino and 433mhz modules.

The plan is to use:

- Arduino + 433mhz module
- http://www.thingiverse.com/thing:1067700 stevenson shield
- BME280 sensor

I did some tests with the BME280 - the accuracy seems to be acceptable so far.
The temperature is a bit too high, one of the sensors had a problem with humidity.

I wondered if anyone else here is running weather stations like this and maybe has some experience
with sensors, sensor placement, Dos and Don'ts.
(Or if there are other forums for this purpose if this is not the right one).

Thanks a lot,
Christoph

Offline vreihen

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Re: Experience with DIY sensors - BME280, etc?
« Reply #1 on: March 07, 2017, 07:47:56 PM »
I bought a batch of I2C BMP280 modules (no humidity) a few months ago.  The thermometers are a convenience sensor for trying to temperature-compensate the barometer, and I wouldn't consider them accurate by any stretch.  The deviation between barometer chips seems to be about 0.12 in-Hg, and they track really nicely against a nearby ASOS once I get them calibrated.  I would personally not use the thermometer for anything but a rough estimate of internal case temperature.

One thing that you want to do is keep the sensor away from *any* moving air.  It is sensitive enough to read the breeze from someone walking by it.  You probably also shouldn't seal it up in an air-tight enclosure, which would probably prevent the outside air pressure from reaching the sensor.....
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Offline vreihen

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Re: Experience with DIY sensors - BME280, etc?
« Reply #2 on: March 07, 2017, 07:59:33 PM »
http://www.wxforum.net/index.php?board=126.0

Before I forget, this thread would probably fit better in the homebrew sub-board under Tech Corner.....
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Offline chbla

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Re: Experience with DIY sensors - BME280, etc?
« Reply #3 on: March 08, 2017, 02:37:01 AM »
@vreihen, thanks for the comments!

Are you talking about the BMP180? Because the 280 do have humidity.
I think sensor placement is obvious - if it's in a sealed case, pressure does not make sense, if it's in a case getting warm, temperature does not make sense.

How exactly did you calibrate it? In order to calibrate accurately the sensors need linear response, otherwise it's getting complicated.

And last but not least: Do you know any better or even calibrated (with certificate) sensors?

Offline 556duckvader

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Re: Experience with DIY sensors - BME280, etc?
« Reply #4 on: March 08, 2017, 04:37:23 AM »
I had a BME280 mounted on a Adafruit Feather Huzzah and Protoboard and I had issues with the temp being high because it was picking up the heat from the Feather.  I ended up connecting it up to a 4 pin cable that was about 6" long and that got rid of the higher temps.

Offline vreihen

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Re: Experience with DIY sensors - BME280, etc?
« Reply #5 on: March 08, 2017, 06:51:47 AM »
Are you talking about the BMP180? Because the 280 do have humidity.

BME280 has humidity, BMP280 does not.

Quote
How exactly did you calibrate it? In order to calibrate accurately the sensors need linear response, otherwise it's getting complicated.

Nothing fancy.  I just did some trial-and-error against the hourly ASOS readings across town until it was reliably tracking within 0.01 in-Hg.  Once I had the first one, I could compare raw readings with the others to see the difference between them sitting side-by-side on the same breadboard.....
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Offline chbla

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Re: Experience with DIY sensors - BME280, etc?
« Reply #6 on: March 08, 2017, 01:10:10 PM »
You're right, I confused the E and P, thanks.

I'll try and see if I can get a good reference to calibrate it

 

anything