As the subject says I have been wondering if the BMP180 sensor could be used to measure the air pressure of an indoor room. I am interested in building a wireless monitor for my workshop and have been looking for a solution to measure how effective my fume extractor fan is. My fan setup is used to exhaust things like paint, stain and some light welding fumes, but I have no way to measure how effective it is in relation to my air intake from doors and windows. There is no need for ultra accurate readings, but I'm looking for something more than a ballpark from smoke movement and how angry my fan gets under back pressure if I close the door too much. If we have any HVAC folks here I would love to know which sensors are used in those types of systems as that is pretty much exactly what my project calls for assuming the BMP180 is not effective indoors.
After some searching I have many more questions than answers such as if I am remotely looking at the right sensor for the job. If not any recommendations are very appreciated, but using the WeatherShield would be great if possible because tracking temperature with humidity really helps with the painting. I have read about people using a MPXV7002DP for air pressure, but most of the projects were for drones and air speed measurement.
I don't have any direct experience with the BMP180 (yet), but in a recent project (https://lowpowerlab.com/forum/index.php/topic,907.0.html), I've used the MS5611 sensor and while there may be some difference between this and the BMP180 in both sensitivity (which you may care about) and conversion speed (which you probably don't care about) this sensor is probably a good benchmark to comment on your question.
UPDATE: Comparing the datasheets for BMP180 & MS5611, it looks as if the pressure sensitivity is virtually the same (0.01hPa BMP180 vs 0.012hPa for the MS5611 - 0.01hPa = 0.004in water) so I'd say the BMP180 should work well for what you want to do.
To test the variometer function I found that all I had to do was open and close the door in my office. This created enough of a pressure difference to effect a significant change in the barometer. From this experience, I'd say it is very likely that the BMP180 will be able to measure the kind of effect you're looking for.
Tom
Thank you for the quick reply and info Tom. I just placed an order for 2 weather shields along with a few other goodies, because can you ever just go into a store for 1 thing and leave with just that one thing? :)
I'll be sure to post updates if anyone else is interested in the results of my testing as soon as the parts arrive.
Quote from: CallOne_Phil on April 05, 2015, 11:47:55 PM
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I'll be sure to post updates if anyone else is interested in the results of my testing as soon as the parts arrive.
Please do. I'd like to hear your results, especially what the pressure difference is.
Tom
I received my order crammed into my cold soggy mailbox today, but thankfully everything was undamaged. I have to hand it to Felix for the quick shipping and great packing that is often unmatched by much higher staffed companies.
After reading up on the examples I was able to get the sample code running. It seems like the temperature reads a little hot and the humidity is a little low next to my old handy digital thermometer. I assume this is just the sensors needing to acclimate and will leave them running awhile to see if the readings fall into line. More testing of this sweet little board to follow :)
Tom,
I think I hit a little bit of a road block with testing my idea of using a pressure sensor to measure the vacuum in a room. I do not seem to be able to generate any meaningful changes (that I have noticed) in my sensor data while opening doors, turning vent fans on/off, etc. I was just wondering if you recalled any details about your setup when you experienced varied readings while testing your MS5611 sensor that might help. It was running the sample code from github and then was switched over to a stripped down version of Felix's GarageMote code to allow me easy remote monitoring via my gateway. All of the sensors appear to be working(very well I might add) and I do get changes from different floors in my house and indoors vs outdoors, but just not from my pressurized workshop like I had hoped.
After more research it seems I might be in the market for a mass airflow sensor, but I have not given up hope yet on this nifty little Shield and I'm still impressed with all the utility it packs into a tiny footprint.
Phil, I assume you're talking about the WeatherShield you got from LPL?
Have the readings stabilized?
Felix, Sorry about that it was was kind of a long day yesterday and I may have glossed over a few key details :)
I am indeed talking about the WeatherShield and the readings did stabilized after as few hours. All of the data I am currently collecting matches up pretty close to my local weather report and my other monitoring devices inside my home when compared. So, I am fairly confident the sensors are functioning normally at this point of my testing.
That's great to hear, thanks for the feedback.
Quote from: CallOne_Phil on April 09, 2015, 11:40:51 PM
Tom,
I think I hit a little bit of a road block with testing my idea of using a pressure sensor to measure the vacuum in a room. I do not seem to be able to generate any meaningful changes (that I have noticed) in my sensor data while opening doors, turning vent fans on/off, etc.
I'm perplexed why you aren't getting a definitive reading if, in fact, the air flow through your shop is being restricted. Since you've measured pressure difference just changing floors (which probably only changes the reading 3-4 points), you have to have a greater amount of pressure change if you are evacuating the space and there is a flow restriction - most fans should be able to easily handle 0.3inches of water static pressure which would be approximately 75 points of difference on the Baro... Either you have nothing to worry about or your fan isn't working at all.
Quote from: CallOne_Phil on April 09, 2015, 11:40:51 PM
I was just wondering if you recalled any details about your setup when you experienced varied readings while testing your MS5611 sensor that might help. <snip...>
Sorry, I don't have any data from that project as I really was focused on relative change over a small time window. I didn't take any specific pressure measurements other than checking to see that the pressure reading was in the ball park when I first fired up the SW.
Tom