AIR FLOW

[nov0798]

I searched but couldnt find. Does anyone have an idea on how to measure airflow using an M1?

 

[electron]

Do you just want to detect if air is flowing, or the CFM value?

 

[Lagerhead]

Does anyone have an idea on how to measure airflow using an M1?

I am (still) interested in the (possibly) related topic of light vacuum measurement, and we had some talk about it here:
http://www.cocoontech.com/index.php?showtopic=10941

Though I haven't tackled the project yet, I was going to try first using a manometer / venturi tube, measuring the light level in the tube with a photoresistor or photodetector. These tubes are quite inexpensive (<$15) and with an op amp and some parts I was expecting (hoping) to get a few linear volts over the active range (0 - 2 inches of water vacuum) with not a lot of cash outlay.

There are some very nice pressure sensors out there, including from Mamac (recently had their surplus current detectors mentioned on the board) and others. But these are more than I care to spend.
http://www.mamacsys.com/pressuretransducers.htm

As Dan points out, if you simply want to get a flow/no-flow indication into your M1, well the M1 is made for that. But getting continuous analog measurements into the Elk is another story. It has been repeatedly discussed on Cocoontech I think without good answers, and I remain hopeful for breakthroughs from the many good minds around here. I tinkered with it but for now I just avoid it. Something like the Barionet might work well. I might go that route to replace some very old analog gear. And read my manometer.

 

[nov0798]

I was hoping to measure cfm, maybe pressure, but definately CFM!

 

[pete]

I was hoping to measure cfm, maybe pressure, but definately CFM!

cfm=airspeed x duct area sqft ..

a hvac tech would take an average of readings, across the width of the duct (it's slower closer to the duct walls)..look to install any detector in straight run of duct to minimize any turbulance..

would be a hack for sure, but how 'bout someting like this ..

http://i179.photobucket.com/albums/w307/Ca...05/136_3632.jpg

would take some tinkering and calibration, but should be doable on the cheap ..

 

[Brightan]

one of the links mentioned had a suggestion to use a automotive air flow sensor and I would echo that. I played with one a few years ago, you just add 12vDC and you get an analog output and it is calibrated for CFM. It doesn't get much easier than that.

 

[electron]

I was looking at those on eBay, you can find them really cheap, but I wasn't sure how you would get the reading. If that's how it works, you could hook it up directly to home automation controller such as the Ocelot, M1, and any other controller supporting analog inputs.

 

[nov0798]

most automotive sensors use a 5v reference signal, not a 12v signal. The 5v signal is then measured by the fuel injection system, and then takes the voltage difference to calculate a value. Most of the time, say 4v = x amount of airflow, and etc. This may not work. This is a typical setup using speed density systems. If you use mass air flow system, you now have to heat a wire within the MAF sensor, again using 5v as a reference signal. This is more trouble than its worth. My Carrier Infinity system has a static pressure, and cfm reading on the controller. I would love to know how to tap into that to the elk.

 

[Brightan]

The unit I was playing with (and I have long forgotten what it was from) was a completely integrated system, 12v in, built in wire heater system with calibrated analog output.