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Pressure switch — Parallax Forums

Pressure switch

MeepoMeepo Posts: 24
edited 2008-06-25 20:03 in BASIC Stamp
· I'm building a BS2 project which uses a switch to sound an alarm when air pressure drops below a preset value. I'm looking for a cheap pressure switch which I can use for up to 120 psi. All of the cheap ones I've found can only take 15-30 psi. Is there a way I can use a small orifice to lower the pressure? I remember I had a turbocharged car and I could adjust the wastegate by changing the size of the orifice - but it seems to me as if given enough time, the air pressure differential across the orifice would eventually allow the pressure to equalize...can anyone either recommend a switch that can take the pressure, or explain how I can drop the pressure enough for a weaker switch to handle it?
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Comments

  • MeepoMeepo Posts: 24
    edited 2008-06-25 14:42
    ·(adding notify by email option)
  • Larry~Larry~ Posts: 242
    edited 2008-06-25 15:11
    Could you give us an Idea of what cheep means in dollars
    there are hundreds of pressure switches
  • Larry~Larry~ Posts: 242
    edited 2008-06-25 15:18
    are you looking for a switch that once set will stay at 120 psi
    also if its static pressure the orifice will not work
  • MeepoMeepo Posts: 24
    edited 2008-06-25 15:38
    Cheap = around $10

    I'm looking for something what will give me either a variable resistance or voltage change with a pressure change. The air pressure will vary from 0-120 psi, I want to know if the pressure drops below 80 or 90 psi, and the ability to log pressure would be great - but I can do that on the BS2 side of things.

    I was thinking of rigging one up with a piece of conductive foam pad and a diaphragm, but an industrial-quality switch or sensor would be better.
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2008-06-25 16:39
    Meepo,

    Why not something like a U-Tube manometer?

    http://www.dwyer-inst.com/htdocs/pressure/manometerintroduction.cfm

    ...This in combination with a capacitive level sensor to sense the fluid level should fall within $10

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • Larry~Larry~ Posts: 242
    edited 2008-06-25 18:45
    Ok so you really don't want a pressure switch

    what you need is a pressure sensor or Transducer
  • Larry~Larry~ Posts: 242
    edited 2008-06-25 19:05
    Go to digi Key they have hundreds of sensors with different outputs and pressure ratings I found a 0 to 200 psig sensor stainless steel with a 0 to 5 volt output for under $70.00 I have paid upwards of $400.00 for pressure transducers.
  • Tim-MTim-M Posts: 522
    edited 2008-06-25 20:03
    How does $2.95 sound?· Take a look at this 100psi·pressure switch from Surplus Center...

    http://www.surpluscenter.com/item.asp?UID=2008062515014615&item=11-2400&catname=

    Tim
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