Cheap Pressure Sensors? Thanks and 2nd Question
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Posts: 46,084
Yeah, I thought about that but all the ones I was
looking at seemed a little too pricey($25 * 12 =
$300), and the little peristalic pumps were even more.
ideally these seem to be the best ideas but, someone
else mentioned the "mariotte siphon", which seems to
be the answer to my problem, constant flow rate over
the entire volume. Ill build one and play with it to
see if it will work. Thanks for all of the feedback,
this group is great!
I have one more question that has perhaps been beaten
to death, I want to do some data logging with Excel on
an old PC, I was thinking VB and MSCOMM to get the
data in and then write it to a file(as soon as I learn
VB), and then have Excel fetch it with the Get Text
feature. I think hyperterminal will also allow
basically the same functionality as reading data and
placing in a text file?? Is this how most of you do
it, does anyone have a completed example I can model
after codewise, or a good reference. Ive looked on
the Net, but there is nothing that really spells out
or gives sample code that I have found. THANKS!!!
Ross Cooper
--- Mark Adams <madams@a...> wrote:
> What I would use is one of those small positive
> displacement pumps. That
> takes the guesswork out of it.
>
> Just my .02
>
> Mark
>
>
Original Message
> From: Klutch [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=w9vclwVKEcSfwkKFlf9nc9GLkVpwf7oyyttso6qhhDcJoDejue8ryrGsdvv5wgWxS4xmKXac5uq0X70]klutch66@y...[/url
> Sent: Wednesday, April 17, 2002 7:45 PM
> To: basicstamps@yahoogroups.com
> Subject: RE: [noparse][[/noparse]basicstamps] Cheap Pressure Sensors?
>
>
> well this will be the 3rd time i try this, my email
> does not seem to be working properly, here goes:
>
> i hope this explins a little better.
> overall problem: track volume of several hoppers of
> different fluids to accurately pour out ounces.
>
> i am buildig a robotic bartender that makes drinks
> by
> looking up the mix from an EEPROM and then activates
> the appropriate solenoid valves to pour out the
> proper
> amounts. I am trying to come up with a way to
> properly pour say 1 oz out of each hopper of fluid.
> The problem is that the velocity flow rate is
> linear(downward slope), not constant. So I need a
> way
> to track how much is in each hopper to open the
> valve
> for the correct amount of time, to properly match
> the
> repective flowrate to volume that changes as the
> fluid
> is poured out. Someone else mentioned that I need
> the
> density, what I planned to do for that was measure
> several types of say gin and average them. Anyway,
> I
> examined several ways to measure the volume via
> capacitance, weight, etc., but the best way both
> functionally and economically, I thought at least,
> was
> to indirectly measure it by finding the pressure
> from
> a custom made manometer. see crude drawing below.
> ___ _ = sealed top
> | | |x| x = pressure sensor -> Stamp
> | | | |
> |^^^^^| |^| ^ = fluid level
> | | | |
> | | | |
> | | | |
> | |__| |
> |_ ______|
> | |
> | |
> [noparse][[/noparse]x] [noparse][[/noparse]x]= solenoid valve(gravity feed)
> | |
> there will be at least 12 of these devices.
>
> I believe that when fluid is placed in the large
> hopper , it will flow into the small hopper joined
> to
> it (3" PVC tube and 1" PVC tube) and because the
> column of air is trapped in the small tube the
> pressure will increase, and therefore I should be
> able
> to fit a curve and get the equation of a line for
> pressure vs volume regardless of liquid. If it was
> a
> constant flow I could just use counters for each
> hopper and open the valves for some constant time,
> but
> I guess that is the ultimate problem at hand. Maybe
> I
> have made this harder than it really is, ideally a
> small pump would work the best, but I am trying to
> minimize my costs, as most people do. I was hoping
> to
> get the sensors for a couple 3 bucks maybe, but I
> guess I'm dreaming. Anyway, If anyone wants to give
> input to my problem, I am more than happy to listen.
> And thank you to those that have given input
> already.
> Ross Cooper
>
>
>
>
>
> --- "Chris Loiacono (E-mail)"
> <chris01@t...> wrote:
> > Ross:
> >
> > As far as I have been able to tell, there are no
> > inexpensive pressure
> > sensors that are designed to tolerate direct
> contact
> > with liquids. Some will
> > do quite well when additional silicone grease is
> > added to protect their
> > internals, however, in a recent exchange with
> > Motorola and another sensor
> > manufacturer the old method of allowing a column
> of
> > the liquid medium to
> > proportionally pressurize dry air above it still
> > remains the standard....Of
> > course, the nice things about this method are that
> > of working with a lower
> > pressure range, and with minimal risk of leakage.
> >
> > Chris
> >
> >
> > > Hello,
> > > I have been looking around for some cheap
> pressure
> > > sensors(digi key seemed to be the cheapest),
> > anyone
> > > know of any good cheap ones, or even a way to
> > "roll my
> > > own" other than with the "black foam stuff"
> method
> > > from IC chips? This is for a liquid application
> > where
> > > I have a some manometers built to measure the
> > volume
> > > indirectly via the pressure. Other methods to
> get
> > the
> > > volume(capacitance, weight, etc.)I believe will
> > not
> > > work as I need to test many different types of
> > fluids
> > > where I do not know what fluid or how much will
> be
> > > added. The pressure seems to be the only fluid
> > > invariant method, unless someone has another
> idea.
> > > Thanks for any help provided,
> > > Ross Cooper
> > >
> > >
> __________________________________________________
> > > Do You Yahoo!?
> > > Yahoo! Tax Center - online filing with TurboTax
> > > http://taxes.yahoo.com/
> > >
> > > To UNSUBSCRIBE, just send mail to:
> > > basicstamps-unsubscribe@yahoogroups.com
> > > from the same email address that you subscribed.
> > Text in the
> > > Subject and Body of the message will be ignored.
> > >
> > >
> > > Your use of Yahoo! Groups is subject to
> > > http://docs.yahoo.com/info/terms/
> > >
> > >
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed.
> > Text in the Subject and Body of the message will
> be
> > ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to
> > http://docs.yahoo.com/info/terms/
> >
> >
>
>
> __________________________________________________
> Do You Yahoo!?
> Yahoo! Tax Center - online filing with TurboTax
> http://taxes.yahoo.com/
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed.
> Text in the Subject and
> Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed.
> Text
=== message truncated ===
__________________________________________________
Do You Yahoo!?
Yahoo! Tax Center - online filing with TurboTax
http://taxes.yahoo.com/
looking at seemed a little too pricey($25 * 12 =
$300), and the little peristalic pumps were even more.
ideally these seem to be the best ideas but, someone
else mentioned the "mariotte siphon", which seems to
be the answer to my problem, constant flow rate over
the entire volume. Ill build one and play with it to
see if it will work. Thanks for all of the feedback,
this group is great!
I have one more question that has perhaps been beaten
to death, I want to do some data logging with Excel on
an old PC, I was thinking VB and MSCOMM to get the
data in and then write it to a file(as soon as I learn
VB), and then have Excel fetch it with the Get Text
feature. I think hyperterminal will also allow
basically the same functionality as reading data and
placing in a text file?? Is this how most of you do
it, does anyone have a completed example I can model
after codewise, or a good reference. Ive looked on
the Net, but there is nothing that really spells out
or gives sample code that I have found. THANKS!!!
Ross Cooper
--- Mark Adams <madams@a...> wrote:
> What I would use is one of those small positive
> displacement pumps. That
> takes the guesswork out of it.
>
> Just my .02
>
> Mark
>
>
Original Message
> From: Klutch [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=w9vclwVKEcSfwkKFlf9nc9GLkVpwf7oyyttso6qhhDcJoDejue8ryrGsdvv5wgWxS4xmKXac5uq0X70]klutch66@y...[/url
> Sent: Wednesday, April 17, 2002 7:45 PM
> To: basicstamps@yahoogroups.com
> Subject: RE: [noparse][[/noparse]basicstamps] Cheap Pressure Sensors?
>
>
> well this will be the 3rd time i try this, my email
> does not seem to be working properly, here goes:
>
> i hope this explins a little better.
> overall problem: track volume of several hoppers of
> different fluids to accurately pour out ounces.
>
> i am buildig a robotic bartender that makes drinks
> by
> looking up the mix from an EEPROM and then activates
> the appropriate solenoid valves to pour out the
> proper
> amounts. I am trying to come up with a way to
> properly pour say 1 oz out of each hopper of fluid.
> The problem is that the velocity flow rate is
> linear(downward slope), not constant. So I need a
> way
> to track how much is in each hopper to open the
> valve
> for the correct amount of time, to properly match
> the
> repective flowrate to volume that changes as the
> fluid
> is poured out. Someone else mentioned that I need
> the
> density, what I planned to do for that was measure
> several types of say gin and average them. Anyway,
> I
> examined several ways to measure the volume via
> capacitance, weight, etc., but the best way both
> functionally and economically, I thought at least,
> was
> to indirectly measure it by finding the pressure
> from
> a custom made manometer. see crude drawing below.
> ___ _ = sealed top
> | | |x| x = pressure sensor -> Stamp
> | | | |
> |^^^^^| |^| ^ = fluid level
> | | | |
> | | | |
> | | | |
> | |__| |
> |_ ______|
> | |
> | |
> [noparse][[/noparse]x] [noparse][[/noparse]x]= solenoid valve(gravity feed)
> | |
> there will be at least 12 of these devices.
>
> I believe that when fluid is placed in the large
> hopper , it will flow into the small hopper joined
> to
> it (3" PVC tube and 1" PVC tube) and because the
> column of air is trapped in the small tube the
> pressure will increase, and therefore I should be
> able
> to fit a curve and get the equation of a line for
> pressure vs volume regardless of liquid. If it was
> a
> constant flow I could just use counters for each
> hopper and open the valves for some constant time,
> but
> I guess that is the ultimate problem at hand. Maybe
> I
> have made this harder than it really is, ideally a
> small pump would work the best, but I am trying to
> minimize my costs, as most people do. I was hoping
> to
> get the sensors for a couple 3 bucks maybe, but I
> guess I'm dreaming. Anyway, If anyone wants to give
> input to my problem, I am more than happy to listen.
> And thank you to those that have given input
> already.
> Ross Cooper
>
>
>
>
>
> --- "Chris Loiacono (E-mail)"
> <chris01@t...> wrote:
> > Ross:
> >
> > As far as I have been able to tell, there are no
> > inexpensive pressure
> > sensors that are designed to tolerate direct
> contact
> > with liquids. Some will
> > do quite well when additional silicone grease is
> > added to protect their
> > internals, however, in a recent exchange with
> > Motorola and another sensor
> > manufacturer the old method of allowing a column
> of
> > the liquid medium to
> > proportionally pressurize dry air above it still
> > remains the standard....Of
> > course, the nice things about this method are that
> > of working with a lower
> > pressure range, and with minimal risk of leakage.
> >
> > Chris
> >
> >
> > > Hello,
> > > I have been looking around for some cheap
> pressure
> > > sensors(digi key seemed to be the cheapest),
> > anyone
> > > know of any good cheap ones, or even a way to
> > "roll my
> > > own" other than with the "black foam stuff"
> method
> > > from IC chips? This is for a liquid application
> > where
> > > I have a some manometers built to measure the
> > volume
> > > indirectly via the pressure. Other methods to
> get
> > the
> > > volume(capacitance, weight, etc.)I believe will
> > not
> > > work as I need to test many different types of
> > fluids
> > > where I do not know what fluid or how much will
> be
> > > added. The pressure seems to be the only fluid
> > > invariant method, unless someone has another
> idea.
> > > Thanks for any help provided,
> > > Ross Cooper
> > >
> > >
> __________________________________________________
> > > Do You Yahoo!?
> > > Yahoo! Tax Center - online filing with TurboTax
> > > http://taxes.yahoo.com/
> > >
> > > To UNSUBSCRIBE, just send mail to:
> > > basicstamps-unsubscribe@yahoogroups.com
> > > from the same email address that you subscribed.
> > Text in the
> > > Subject and Body of the message will be ignored.
> > >
> > >
> > > Your use of Yahoo! Groups is subject to
> > > http://docs.yahoo.com/info/terms/
> > >
> > >
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed.
> > Text in the Subject and Body of the message will
> be
> > ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to
> > http://docs.yahoo.com/info/terms/
> >
> >
>
>
> __________________________________________________
> Do You Yahoo!?
> Yahoo! Tax Center - online filing with TurboTax
> http://taxes.yahoo.com/
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed.
> Text in the Subject and
> Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed.
> Text
=== message truncated ===
__________________________________________________
Do You Yahoo!?
Yahoo! Tax Center - online filing with TurboTax
http://taxes.yahoo.com/
Comments
>Yeah, I thought about that but all the ones I was
>looking at seemed a little too pricey($25 * 12 =
>$300), and the little peristalic pumps were even more.
> ideally these seem to be the best ideas but, someone
>else mentioned the "mariotte siphon", which seems to
>be the answer to my problem, constant flow rate over
>the entire volume. Ill build one and play with it to
>see if it will work. Thanks for all of the feedback,
>this group is great!
One last idea - if you can place the container to be filled on a digital
scale you can weigh the ingredients. A serial port is readily available on
such scales.
Jim H