Our Valued Sponsor
OpinionsConsumer ReviewsGuides and How TosCoffeeGeek ReviewsResourcesForums
Espresso: Espresso Mods and Restorations
Water level sensing circuit
The Coffee Project
Home coffee Roasting equipment, green beans, and supplies
www.coffeeproject.com
 
Not Logged in: Log In to Postlog in
New Topics updated topics   New Posts new posts   Unanswered Posts new unanswered  
Search Discussion Board search   Discussion Board FAQ faq   Signup sign up  
Discussions > Espresso > Espresso Mods > Water level...  
view previous topic | view next topic | view all topics
showing page 1 of 2 last page next page
Author Messages
TRUgEEk
Senior Member


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

Posted Sat Aug 18, 2012, 5:26pm
Subject: Water level sensing circuit
 

Does anyone have a suggestion for how to monitor the FULL level with a standard single probe? Capacitance sensing techniques? Knowing when the sensor  is out of the water is pretty easy. I'm not familiar with how to know it's full.
back to top
 View Profile Link to this post
calblacksmith
Moderator
calblacksmith
Joined: 25 Nov 2007
Posts: 8,042
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 Tue Aug 21, 2012, 9:11am
Subject: Re: Water level sensing circuit
 

Most circuits use a probe into the boiler. When the circuit is completed by the water level in the tank rising to touch the probe, the tank is full. The level is maintained by a simple on/off circuit set to the full level of the boiler. Either the boiler is full or the pump turns on to make it full, it is as simple as that.

 
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!
back to top
 View Profile Visit website Link to this post
TRUgEEk
Senior Member


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

Posted Tue Aug 21, 2012, 12:51pm
Subject: Re: Water level sensing circuit
 

Thank you for the reply. I'm confused though - wouldn't the logic you described cause the pump to constantly cycle on and off? Is there some sort of timer involved as well to keep the pump off for some period after filling?

I'm redesigning/replacing the control logic on an older machine and would like to make improvements along the way. Your post is helpful because I hadn't considered that the probe's position is possibly at the full rather than low level. How much water is typically maintained in an HX boiler? Just enough to keep the elements covered?

Thank you for any help you can provide.
back to top
 View Profile Link to this post
TRUgEEk
Senior Member


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

Posted Wed Aug 22, 2012, 2:52am
Subject: Re: Water level sensing circuit
 

I can see two "high water lines" inside the boiler. The lower of the two is formed by a thicker layer of scale which coats the entire bottom 2/3 or so of the boiler and would seem to be at the level of the probe. The less apparent line is about 3/4 to 1" higher and probably corresponds to the "full" level. The volume of the delta is about 0.5-0.75 L or so. That seems like a reasonable working volume between fills. I will test just running a timer from when the probe is uncovered to see how repeatable this volume is based on my water pressure and pump.
back to top
 View Profile Link to this post
calblacksmith
Moderator
calblacksmith
Joined: 25 Nov 2007
Posts: 8,042
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 Wed Aug 22, 2012, 5:11am
Subject: Re: Water level sensing circuit
 

Yes, the pump refills the boiler often, mine runs for about 3 seconds when it fills the boiler so you likely are correct about the timer but the only sensor is the one probe into the boiler and it is a simple on/off type of thing. The size of your boiler and type of pump will have a lot to do also with how long the pump runs. If you have a 2.5l boiler like mine with a rotary pump, three seconds is one thing but if you ran the same pump for the same time in a machine with a 8 oz boiler, I would guess it would constantly be venting water from the overflow.

 
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!
back to top
 View Profile Visit website Link to this post
TRUgEEk
Senior Member


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

Posted Wed Aug 22, 2012, 9:32am
Subject: Re: Water level sensing circuit
 

About how often does your pump kick on if you are steaming? My boiler is 4L and I have a rotary pump rated at 200L/hr -> 0.7L in 3 secs. That's obviously in the range. I hope to calibrate mine tonight. I know that the standard way of filling is to use the single probe as an on/off, but there are other techniques like measuring the capacitance with potentially finer resolution and less chance of false readings once the probe gets corroded. That said, if the simple single probe works, then it may be good enough. My biggest hesitation is that many machines seem to fail because of auto fill malfunctions. Mine did! The doser failed which caused a cascade that took out the heating element. By measuring capacitance it could be possible to detect scale buildup on the probe before it's too late.
back to top
 View Profile Link to this post
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 Wed Aug 22, 2012, 7:54pm
Subject: Re: Water level sensing circuit
 

Hey Bill -

When I had my Silvia, I did make a water level sensing circuit using a proximity sensing IC.  I used de-soldering braid as the water level sensing electrode, around the exterior of the water tank, i.e. there was no internal probe in sitting in the water.  I used the QT113-DG QPROX SENSOR, DIP8, 113 (Newark Electronics Part Number: 92K8427).

Below is a picture of the PC i built for the IC.  You can read a bit about it on my Blog.  If you look all around the blog, there is a complete parts list too.

Best,

Rick

rsinger: WLS Circuit board on wall.jpg
(Click for larger image)

 
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
back to top
 View Profile Visit website Link to this post
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 Wed Aug 22, 2012, 7:58pm
Subject: Re: Water level sensing circuit
 

Here is a picture of the sensor electrode that I had used as well.

Keep in mind that in my application, the digital output of this circuit was read by Arduino.  My code was designed to act as a "Low water level sensor", printing to the LCD "Add H2O".  However, there is no reason that the sensor electrode could not be placed high on the tank, and then the code could be written to sense a "Full" tank.


Hope you find this helpful.

rsinger: Water Tank and Sensor.jpg
(Click for larger image)

 
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
back to top
 View Profile Visit website Link to this post
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 Wed Aug 22, 2012, 8:04pm
Subject: Re: Water level sensing circuit
 

One last image:

rsinger: Water Tank & Sensor & Wall.jpg
(Click for larger image)

 
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
back to top
 View Profile Visit website Link to this post
TRUgEEk
Senior Member


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

Posted Thu Aug 23, 2012, 1:23am
Subject: Re: Water level sensing circuit
 

Thanks Rick! Nice work.

Unfortunately it looks like the QT113 is no longer in production. There is an Atmel part (QT1010) which is similar, but specifically designed for touch sensing. I've been playing around with the Arduino Capsense library which calculates an RC circuit's time constant. I don't know if I can create a reliable environment or the magnitude of the capacitance I'd be dealing with. I also don't know how much the temperature flucuations will affect the capacitance. I really don't want to do all those calculations (it's been too long ago...) but I'll have to have at least some rough estimates to stabilize the circuit I think. My boiler is a copper tank that is about 8" in diameter and 8" long. I will probably get the simple logic with a timer to work (so I can make coffee again!!) and work on this in parallel.
back to top
 View Profile Link to this post
showing page 1 of 2 last page next page
view previous topic | view next topic | view all topics
Discussions > Espresso > Espresso Mods > Water level...  
New Topics updated topics   New Posts new posts   Unanswered Posts new unanswered     Search Discussion Board search   Discussion Board FAQ faq   Signup sign up  
Not Logged in: Log In to Postlog in
Discussions Quick Jump:
Symbols: New Posts= New Posts since your last visit      No New Posts= No New Posts since last visit     Go to most recent post= Newest post
Forum Rules:
No profanity, illegal acts or personal attacks will be tolerated in these discussion boards.
No commercial posting of any nature will be tolerated; only private sales by private individuals, in the "Buy and Sell" forum.
No SEO style postings will be tolerated. SEO related posts will result in immediate ban from CoffeeGeek.
No cross posting allowed - do not post your topic to more than one forum, nor repost a topic to the same forum.
Who Can Read The Forum? Anyone can read posts in these discussion boards.
Who Can Post New Topics? Any registered CoffeeGeek member can post new topics.
Who Can Post Replies? Any registered CoffeeGeek member can post replies.
Can Photos be posted? Anyone can post photos in their new topics or replies.
Who can change or delete posts? Any CoffeeGeek member can edit their own posts. Only moderators can delete posts.
Probationary Period: If you are a new signup for CoffeeGeek, you cannot promote, endorse, criticise or otherwise post an unsolicited endorsement for any company, product or service in your first five postings.
Rocket R58 Double Boiler
Rocket Espresso R58 Double Boiler -  Everything you need for the perfect shot!
www.seattlecoffeegear.com
Home | Opinions | Consumer Reviews | Guides & How Tos | CoffeeGeek Reviews | Resources | Forums | Contact Us
CoffeeGeek.com, CoffeeGeek, and Coffee Geek, along with all associated content & images are copyright ©2000-2014 by Mark Prince, all rights reserved, unless otherwise indicated. Content, code, and images may not be reused without permission. Usage of this website signifies agreement with our Terms and Conditions. (0.259606838226)
Privacy Policy | Copyright Info | Terms and Conditions | CoffeeGeek Advertisers | RSS | Find us on Google+