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From: Rich Grise on 5 Jul 2006 19:25 On Wed, 05 Jul 2006 21:01:14 +0000, Joerg wrote: > Hello James, > >> >> ... I would like to also be able to >> determine the amount remaining in the system if it isn't all pumped in the >> time allotted. >> > > Now that's more luxury than you mentioned at first. Some ideas that > might or might not work in your case: > > a. A gas gauge mechanism from a car. Might corrode out over time. > > b. Sound transducers (old piezos, whatever) fastened to the side of the > barrel at equal distances. You could use a uC such as the MSP430, a > version with enough ADC muxes to excite and then scan them sequentially. > This could also calculate the approximate contents and report in > gallons, liters, jars, buckets, number of remaining toilet flushes or > whatever is preferred. > > c. PVC pipe with end cap, must be absolutely water tight. Copper pipe in > the middle that has an OD almost as large as the ID of the PVC pipe. > Connect oscillator circuit to it. This forms a capacitor where the > capacitance changes with the water level. This in turn changes the > frequency but it won't be linear. Follow with a little F/V detection and > you'd have a nice analog readout. Add a comparator that shuts off the > pump below a chosen threshold. > > d. Stainless contacts inside, equidistant, with the lowest being the > level where you want to pump to cut out. Connect to a stack of > comparators a la LM339 and then to a row of LED. The lowest one > deactivates the pump when the contact goes open. > > Of course, some of this depends on your water and other things. Do you mean, the copper middle electrode is completely insulated from the water? If that's all you need, you could paint it. How about a stainless steel rod inside a stainless steel tube, where the water is the dielectric between these two - i.e., the level on the inside is the same as the level on the outside. That is, I'm thinking that the water goes up inside the capacitor tube, but your description of an "absolutely water tight" construction makes me wonder what you have in mind. ?:-/ Thanks! Rich
From: Joerg on 5 Jul 2006 20:42 Hello Rich, >> >>c. PVC pipe with end cap, must be absolutely water tight. Copper pipe in >>the middle that has an OD almost as large as the ID of the PVC pipe. >>Connect oscillator circuit to it. This forms a capacitor where the >>capacitance changes with the water level. This in turn changes the >>frequency but it won't be linear. Follow with a little F/V detection and >>you'd have a nice analog readout. Add a comparator that shuts off the >>pump below a chosen threshold. > > Do you mean, the copper middle electrode is completely insulated from the > water? If that's all you need, you could paint it. How about a stainless > steel rod inside a stainless steel tube, where the water is the dielectric > between these two - i.e., the level on the inside is the same as the level > on the outside. > > That is, I'm thinking that the water goes up inside the capacitor tube, > but your description of an "absolutely water tight" construction makes > me wonder what you have in mind. ?:-/ > Even rain water can be aggressive. When I lived in Europe there were times when I got rain in the eyes and they started buring. Same back east. Has gotten better though. Paint, exposed metal, all that will rot over time. I have even seen steel corrode although it was sold as stainless. In an application like this ideally you need something that you can build and forget for a few years. -- Regards, Joerg http://www.analogconsultants.com
From: Jim Thompson on 5 Jul 2006 20:49 On Thu, 06 Jul 2006 00:42:01 GMT, Joerg <notthisjoergsch(a)removethispacbell.net> wrote: >Hello Rich, > [snip] > >Even rain water can be aggressive. When I lived in Europe there were >times when I got rain in the eyes and they started buring. [snip] That French smog drifting into Germany? Really ugly when looking west across the Rhein from a high spot in the Black Forest. ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Joerg on 5 Jul 2006 21:06 Hello Jim, > >>Even rain water can be aggressive. When I lived in Europe there were >>times when I got rain in the eyes and they started buring. > > That French smog drifting into Germany? Really ugly when looking west > across the Rhein from a high spot in the Black Forest. > Not up there near my alma mater. We were surrounded by power plants and other plants that burned surface-mined coal. High in sulfur content and all that. Depending on where you parked it could etch the paint on a car. Regards, Joerg http://www.analogconsultants.com
From: Rich Grise on 5 Jul 2006 21:46
On Thu, 06 Jul 2006 00:42:01 +0000, Joerg wrote: > Hello Rich, > >>> >>>c. PVC pipe with end cap, must be absolutely water tight. Copper pipe in >>>the middle that has an OD almost as large as the ID of the PVC pipe. >>>Connect oscillator circuit to it. This forms a capacitor where the >>>capacitance changes with the water level. This in turn changes the >>>frequency but it won't be linear. Follow with a little F/V detection and >>>you'd have a nice analog readout. Add a comparator that shuts off the >>>pump below a chosen threshold. >> >> Do you mean, the copper middle electrode is completely insulated from the >> water? If that's all you need, you could paint it. How about a stainless >> steel rod inside a stainless steel tube, where the water is the dielectric >> between these two - i.e., the level on the inside is the same as the level >> on the outside. >> >> That is, I'm thinking that the water goes up inside the capacitor tube, >> but your description of an "absolutely water tight" construction makes >> me wonder what you have in mind. ?:-/ >> > > Even rain water can be aggressive. When I lived in Europe there were > times when I got rain in the eyes and they started buring. Same back > east. Has gotten better though. > That's called "acid rain" - it's from burning sulfur-rich coal, which makes SO2 and SO3, which turns to H2SO4 when it hits water vapor. =:-O > Paint, exposed metal, all that will rot over time. I have even seen > steel corrode although it was sold as stainless. In an application like > this ideally you need something that you can build and forget for a few > years. And your objection to making a yearly inspection of your facilities would be....? ;-) Thanks, Rich |