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gas flow sensor — Parallax Forums

gas flow sensor

JW SmytheJW Smythe Posts: 12
edited 2006-11-05 14:45 in General Discussion
G'morning.

I'm looking for a gas flow sensor to attach to my basic stamp.

I'm still playing with that 'run your car on hydrogen' thing. It seems like a neat idea, so why not play, right? Some people play with model trains. Some people build tiny ships in bottles. I play with electricity and explosive gases. [noparse]:)[/noparse]

The HV thing didn't work out for it. It was fun though.

I'm attempting to do what a few companies are claiming works, pulsing the power to an electrolysis rig. Honestly, I see nothing spectacular, but I'm sitting here playing with frequencies and watching the bubbles. My setup has 8 going to a SSR, and 14 going to a LED


HIGH 8
HIGH 14
PAUSE I
LOW 8
LOW 14
PAUSE I/9

AND

FREQOUT 8,2000, I

In the first sample, I've tried I as 1 to 1000. In the second, I've tried I as 1 to 100.

I need some real numbers to associate with the results though, other than "bubbles." The rig can be set up air tight. While I'm playing, it's open to the air, and I'm testing outside so I don't blow myself up. [noparse]:)[/noparse]

I found a thread where someone else had asked for a LP control system, but the last post said he found a place that may have something, and he'd post more later, with no "more" to be found.

Basically, I'd like to close it up air tight, except for a vent with a flow sensor on it. Any ideas for a sensor?

I thought I may use a pressure sensor, but that'll be hard to really evaluate what the box is doing. I'd like to write the program to go through a whole bunch of tests a minute or so long, and just let it run overnight. In the morning, I can go through the results, and see if there is any change at any particular set of values.

I suspect that I can get away with pulsing the power somewhere below hooking it straight up to DC, and lower the power demands of the box. I need to find that magic point, where it uses less power, but doesn't reduce gas flow. Once I know that, I can stuff the box full of electrodes, and see what it can do.

Comments

  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2006-11-04 16:29
    Parallax has a 'vibration sensor' that might be adaptible.

    It is a thin piezoelectric layer embedded in plastic. If it were inside a tube, the turbulence from the flow of the gas might excite it and provide predictible data.

    The biggest dilemma you have is that H2 is both small molecules·and explosive. Leakages and electrical sparks just raise all sorts of questions of safety.

    If you were to go shopping for an off the shelf device, I suspect that it would be quite costly due to safety certifications involved.· One alternative is to have the vibration sensor measure the shake in turburlance inside an elbow.· The gas would be completely separate from the electronics.· The elbow would have to be flex mounted and the shake sensor would be on the outside.


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    "If you want more fiber, eat the package.· Not enough?· Eat the manual."········
    ···················· Tropical regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

    Post Edited (Kramer) : 11/4/2006 4:33:10 PM GMT
  • JW SmytheJW Smythe Posts: 12
    edited 2006-11-04 17:39
    Hmmm, I didn't think of the vibration sensor. I'd be afraid that it may be influenced by other factors, such as the pulse rate.

    I'm not terribly worried about the explosion factor. I'm keeping a safe distance when I'm testing. If it does pop, it'll just give me something else to fiddle with. [noparse]:)[/noparse] The biggest concern would be me waking up to a loud pop outside the house. [noparse]:)[/noparse]
  • tech-mechtech-mech Posts: 14
    edited 2006-11-05 01:07
    Gas flow can be found by the difference in pressure across a square edge orifice. If you only need to know change in flow you would not need to calibrate it. Find a book on fluid flow for more information.

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    Dale Bartel

    Portland Or
  • HulkHulk Posts: 68
    edited 2006-11-05 14:45
    You could use a scaled-down mass airflow sensor as used in electronic fuel injected car engines. These sensors are hot wire anemometers. In general, a wire in the gas stream is heated to, I think, a constant temperature. The current used to maintain this temperature is proportional to the mass of the gas flowing across the element. I may be off in the detail of operation, but this may give you a system to study.

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