Prev: conservation of Euros
Next: SMPS "S" terminals & V adj.
From: mpm on 21 May 2010 20:26
On May 20, 10:28 pm, "lektric....(a)gmail.com" <lektric....(a)gmail.com>
wrote:
> I'm working on a project to help develop a solar powered water pump.
> The pump is called a fluidyne, essentially a liquid piston Sterling
> engine.  You can find more about the project here:http://www.iedu.com/DeSoto/Fluidyne/
> What I would like to do is build a small fluidyne that I can put a
> specific, controlled amount of heat into, and measure the results.
> I'd like to find a source for (very) inexpensive pressure sunsors.
> They need to be able to measure very small pressures (50 cm water
> pressure).  I've got all kinds of interface circuitry, so I can
> measure a sensor that uses a strain gauge (in whatever configuration),
> simple resistance changes, piezoelectric, or whatever.  Any ideas or
> sources?

Do you need to measure pressure, or just need a switch function at a
given pressure (+/-)?
Try: http://www.designflexswitches.com/ or Google "World
Magnetics".
I think Digikey might carry them, or just ask the manufacturer for a
sample.

We had a similar design a while back and these switches worked fine.
Our was air; I can only assume a water column would be even easier.

Good luck. -mpm
From: Michael A. Terrell on 21 May 2010 20:53

Jim Thompson wrote:
>
> On Sat, 22 May 2010 08:07:43 +1000, Grant <omg(a)grrr.id.au> wrote:
>
> >On Fri, 21 May 2010 14:40:14 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote:
> >
> >>On Sat, 22 May 2010 07:36:38 +1000, Grant <omg(a)grrr.id.au> wrote:
> >>
> >>>On Fri, 21 May 2010 07:13:21 -0700 (PDT), George Herold <gherold(a)teachspin.com> wrote:
> >>>
> >>>>On May 20, 11:28 pm, "lektric....(a)gmail.com" <lektric....(a)gmail.com>
> >>>>wrote:
> >>>>> I'm working on a project to help develop a solar powered water pump.
> >>>>> The pump is called a fluidyne, essentially a liquid piston Sterling
> >>>>> engine. You can find more about the project here:http://www.iedu.com/DeSoto/Fluidyne/
> >>>>> What I would like to do is build a small fluidyne that I can put a
> >>>>> specific, controlled amount of heat into, and measure the results.
> >>>>> I'd like to find a source for (very) inexpensive pressure sunsors.
> >>>>> They need to be able to measure very small pressures (50 cm water
> >>>>> pressure). I've got all kinds of interface circuitry, so I can
> >>>>> measure a sensor that uses a strain gauge (in whatever configuration),
> >>>>> simple resistance changes, piezoelectric, or whatever. Any ideas or
> >>>>> sources?
> >>>>
> >>>>I've used Honeywell 24PC and 26PC series sensors's $15 and $23 each..
> >>>>is that cheap? I'm not sure if they work in fluids.
> >>>
> >>>Like the washing machine sensors, they's work with pressurised a
> >>>column of air from the pipe down to the bottom of the tub, no?
> >>>
> >>>Grant.
> >>
> >>Yep, But I've never quite understood how they maintain any accuracy...
> >>I guess � a couple of inches is OK ?:-)
> >
> >On my washing machine there's a position to far clockwise labeled
> >'Reset', but I've never dismantled one to see how they work :)
> >
> >Grant.
>
> Same here. I have no idea, but my curiosity is tweaked :-)


That can be quite painful! ;-)


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.
From: Ecnerwal on 21 May 2010 22:22
In article
<4bdc56ae-d7da-4fbf-bb91-049d8536f033(a)m4g2000vbl.googlegroups.com>,
"lektric.dan(a)gmail.com" <lektric.dan(a)gmail.com> wrote:

> I'm working on a project to help develop a solar powered water pump.
> The pump is called a fluidyne, essentially a liquid piston Sterling
> engine. You can find more about the project here:
> http://www.iedu.com/DeSoto/Fluidyne/
> What I would like to do is build a small fluidyne that I can put a
> specific, controlled amount of heat into, and measure the results.
> I'd like to find a source for (very) inexpensive pressure sunsors.
> They need to be able to measure very small pressures (50 cm water
> pressure). I've got all kinds of interface circuitry, so I can
> measure a sensor that uses a strain gauge (in whatever configuration),
> simple resistance changes, piezoelectric, or whatever. Any ideas or
> sources?

Mouser and newark have various sensors that look like they would work
for $5 to $11 (as well as other ones that run into the hundred$) so it
depends what you mean by (very), and whether availability without
dicking around with surplus is worth anything to you. Mouser is better
at the low end of that price range.

Agony at a very low cost is available by using a manometer tube and a
bunch of optical sensors that switch when there's water rather than air
in the tube - though by the time you get enough of them on there for
resolution, it might not be so cheap after all.

--
Cats, coffee, chocolate...vices to live by
From: tm on 21 May 2010 22:51

"Ecnerwal" <MyNameForward(a)ReplaceWithMyVices.Com.invalid> wrote in message
news:MyNameForward-E96DAD.22223821052010(a)mx03.eternal-september.org...
> In article
> <4bdc56ae-d7da-4fbf-bb91-049d8536f033(a)m4g2000vbl.googlegroups.com>,
> "lektric.dan(a)gmail.com" <lektric.dan(a)gmail.com> wrote:
>
>> I'm working on a project to help develop a solar powered water pump.
>> The pump is called a fluidyne, essentially a liquid piston Sterling
>> engine. You can find more about the project here:
>> http://www.iedu.com/DeSoto/Fluidyne/
>> What I would like to do is build a small fluidyne that I can put a
>> specific, controlled amount of heat into, and measure the results.
>> I'd like to find a source for (very) inexpensive pressure sunsors.
>> They need to be able to measure very small pressures (50 cm water
>> pressure). I've got all kinds of interface circuitry, so I can
>> measure a sensor that uses a strain gauge (in whatever configuration),
>> simple resistance changes, piezoelectric, or whatever. Any ideas or
>> sources?
>
> Mouser and newark have various sensors that look like they would work
> for $5 to $11 (as well as other ones that run into the hundred$) so it
> depends what you mean by (very), and whether availability without
> dicking around with surplus is worth anything to you. Mouser is better
> at the low end of that price range.
>
> Agony at a very low cost is available by using a manometer tube and a
> bunch of optical sensors that switch when there's water rather than air
> in the tube - though by the time you get enough of them on there for
> resolution, it might not be so cheap after all.


How about a coaxial electrode in the one end of the manometer with a
dielectric fluid and measure the change in capacitance as the fluid
displaces the air?

Tom


From: whit3rd on 21 May 2010 23:36
On May 20, 8:28 pm, "lektric....(a)gmail.com" <lektric....(a)gmail.com>
wrote:
> I'm working on a project to help develop a solar powered water pump.

> I'd like to find a source for (very) inexpensive pressure sunsors.
> They need to be able to measure very small pressures (50 cm water
> pressure).  I've got all kinds of interface circuitry...

And, it all has to fit down a well?

Best pressure sensing is done by measuring the force that
returns a diaphragm to the zero position (or piston, or
column of mercury... whatever). So, you could bleed air from
a compressor tank until it balances the water pressure, and
measure that. It'd be possible to put any number of two-port
pressure switches in a system, with air on port #2, and
ramp up the air pressure until each one changes state.

A mercury column might be (toxic and) inconvenient to
arrange (50 cm water means only a few cm of Hg, though),
but it can be capacitively sensed for readout. A water
column hasn't got repeatable conductivity, and only a DENSER
fluid than water is suitable for a U-tube (which means mercury
or CCl4 or ... what else?) Your liquid column would
have to be protected against contamination, though.

It's possible to use a piezoresistive sensor (like all those
solid-state MAP sensors in automobiles),
but the prices scare me.

Bourdon tube gages (the rotary-dial familiar kind) can easily be
fitted with variable capacitors or Gray-code scales (one needs
low friction or you could use potentiometers), but I'm not familiar
with any suppliers of such.
First  |  Prev  |  Next  |  Last
Pages: 1 2 3 4
Prev: conservation of Euros
Next: SMPS "S" terminals & V adj.