limaunion
Posts: 18
Joined: Sun Mar 11, 2012 1:49 pm

BMP085: two questions

Fri Apr 12, 2013 12:43 am

Hi I'm a newbie in electronics. I just want to build a pressure/temp sensor by using this module. I've been looking on ebay and there're lots of them for just $4 or $5 us dollars. In general, are they fake or real bosch sensors? what is the max distance permitted between the module and the GPIO? TIA.
LU

stijn.ghesquiere
Posts: 26
Joined: Sat May 19, 2012 9:44 pm

Re: BMP085: two questions

Fri Apr 12, 2013 9:57 am

I got a cheap one from ebay. It works perfectly well. I use the Adafruit python library to get it working, which it did at once. It has very little noise and it's very sensitive. It perfecty suits my needs, and teh fact that it also supplies temperature readings is very nice.
I have no idea how long the lines can be. I think that if you use quality cabling and lower bus speeds, you can easily stretch it to a few meter. But I guess trial and error would give you some idea. If mine weren't build in and running, I could test it for you.

limaunion
Posts: 18
Joined: Sun Mar 11, 2012 1:49 pm

Re: BMP085: two questions

Fri Apr 12, 2013 11:49 am

hi! thanks for your comments, I'll buy a couple of them from ebay and regarding the distance, I'll do some tests. My idea is to build a weather station and this is the starting point.
Best regards.
LU

rj999
Posts: 31
Joined: Wed Feb 01, 2012 12:22 pm

Re: BMP085: two questions

Fri Apr 12, 2013 9:00 pm

Bought mine from a cheap Ebay seller. It arrived from China within a fortnight. It is within .1hPa of the one that's built in to my WH1081 weather station so I would think it's safe to buy cheaply. I now have it on the Pi's I2C local buss, but there is also a bh1750fvi I2C light sensor about 50 feet away up a pole, using a pair of P82B715 buss extenders to allow the long cable distance to the sensor. The 715 pdf says a pair can provide I2C cable distances of up to 50Metres, though I'm not sure how the local 3.3V Pi power source would like driving that distance! I'm using cat 5e cable with them.

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