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Water level sensing circuit
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calblacksmith
Moderator
calblacksmith
Joined: 25 Nov 2007
Posts: 7,772
Location: Riverside, Ca, U.S.A.
Expertise: I live coffee

Espresso: ECM Vene. A1, La Cimbali M32
Grinder: Azkoyen Capriccio, Major
Vac Pot: 40s era Silex
Drip: Msl. Com. brewers
Roaster: gave it a try, decided no
Posted Thu Aug 23, 2012, 11:12am
Subject: Re: Water level sensing circuit
 

Well a much more advanced voice than mine has spoken, thankyou!

I try to stay with the KISS method myself.

You could use two probes, one for low level and one for full.
YMMV!

 
In real life, my name is
Wayne P.
Anything I post is personal opinion and is only worth as much as anyone else's personal opinion. YMMV!

Feed the newbs, starve the trolls and above all enjoy what you drink!
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rsinger
Senior Member
rsinger
Joined: 25 Jan 2008
Posts: 188
Location: Boca Raton, Florida
Expertise: I like coffee

Espresso: Bezzera Strega
Grinder: OE Pharos - #136!!  ;)
Posted Thu Aug 23, 2012, 7:35pm
Subject: Re: Water level sensing circuit
 

Hi Bill

There was also a QT114-DG, but I wouldn't be surprised if you contacted the Quantum Research Group or Atmel that they might be able to assist:

North America
651 Holiday Drive Bldg. 5 / 300
Pittsburgh, PA 15220 USA
Tel: 412-391-7367
Fax: 412-291-1015

or Atmel Corp

Atmel Corporate Headquarters
1600 Technology Drive
San Jose, California 95110 United States
Phone: 408-441-0311
Web: http://www.atmel.com/

They might be able to recommend an IC with similar properties that you could use.  I remember when I was working on the circuit, that the real challenge, given the metal enclosure that the circuit sits in (i.e., inside the espresso machine) and the proximity to the boiler and other electrical interferences, was finding the right balance between the reference and measurement capacitance.  At one point, any time I came within 5 feet of Sylvia, the LCD told me to "Add H2O"!  Eventually, I got it right!  Also, at least with the QT113, the ambient temperature inside Sylvia's case was not a problem.

Good luck!


Rick

 
New Bezzera Strega
OE Pharos: #136!!
Silvia's a virgin.....  again! (and sold)
Brasilia Cappuccino Del-1 Hx (sold too)
http://www.flickr.com/photos/66189160@N04/sets/72157628015297112/show/
http://espressoproject.blogspot.com/2008_10_01_archive.html
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TRUgEEk
Senior Member


Joined: 6 Aug 2012
Posts: 20
Location: east coast
Expertise: I love coffee

Posted Thu Aug 23, 2012, 9:02pm
Subject: Re: Water level sensing circuit
 

You could use two probes, one for low level and one for full.
YMMV!

Thanks Wayne. I think that's a great approach, but I don't want to fool around with adding another port on the boiler at this point. I will probably do that once I build my own tank :-)
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TRUgEEk
Senior Member


Joined: 6 Aug 2012
Posts: 20
Location: east coast
Expertise: I love coffee

Posted Thu Aug 23, 2012, 9:08pm
Subject: Re: Water level sensing circuit
 

Thanks Rick. I did a rough calculation and the capacitance change is probably on the order of a few picoFarads. I'm not sure it's worth the effort to get this working versus just a couple of simple probes as Wayne suggested. The main attraction is that the simple probe approach is prone to accumlating scale due to the DC. I may try and come up with a simple AC scheme that just uses a high and low level.
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