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Need help detecting water level of boiling water. — Parallax Forums

Need help detecting water level of boiling water.

matts persicmatts persic Posts: 3
edited 2006-11-25 06:48 in Learn with BlocklyProp
I am building an automated appliance to brew a cup of tea for my senior computer science project (university).· I am using a BS2.· I have run into a problem in trying to figure out how to detect the water levels in: 1) the brewing chamber, and 2) the·user's tea cup as it fills with the near-boiling tea.

The brewing chamber is a stainless open top container and I need to detect the level at full and empty for when the container is filling.· I could use a simple wire probe but I am concerned that moisture will accumulate on the insulator and the reading will be inaccurate over time.· I would like to use the Parallax PING))), but the brewing chamber is also the chamber where the water is brought up to boiling temperature, so I am afraid the steam will damage the PING))) unit.

For the tea cup, I need to sense the level as it fills with hot tea.· Again I am concerned about the PING))) being damaged from steam.· A probe will not work because it would be in the way (or may be thrown out of alignment) when the user places/removes the tea cup.

I would greatly appreciate any suggestions.· (I will gladly accept collect calls if you have any experience with this in industry and want to explain it via telephone).

General background: I am a Comp Sci major, so mechanics are out of my league.· The project is to demonstrate process control and factory automation.· To this end, I am employing an RFID reader to read an embedded tag in the tea cup to bill and also·control the brew strength preference of each user, also a robotic arm to place (and retrieve) the tea bag in the brewing chamber, a TSL230 Light to Frequency sensor to determine the brew strength (based on light transmittance) and a GSM/GPRS module to send a SMS text message to notify the user when their cup of tea is ready.

Thank you.

Matts Persic
14231 Komedal Road, NE - Bainbridge Island, WA - 98110
mattspersic@comcast.net
+1 206 931-1653 United States
+44 (77) 93827641 UK

Comments

  • Bruce BatesBruce Bates Posts: 3,045
    edited 2006-11-24 12:26
    Matts -

    This may be an excellent application for a couple of capacitive sensors. Quantum Research has some real nice sensors, and usually will provide samples which is important in a self-funded university project. You can check their offerings here: http://www.qprox.com/

    If for some reason that doesn't meet your needs, shout back, as there are many ways to approach this problem.

    Good luck with your project!

    Regards,

    Bruce Bates

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  • CCraigCCraig Posts: 163
    edited 2006-11-24 15:13
    Just an idea, the tag on the cup might indicate the cup size also. Time the flow.



    HTH, Chris
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2006-11-24 15:45
    Keep it simple and use a float switch.

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    ···················· Tropical regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2006-11-24 17:13
    http://www.amazon.com/Sunbeam-Hot-Shot-Beverage-Machine/dp/B00006IUZ5

    · smilewinkgrin.gif··
  • Tommy BotTommy Bot Posts: 60
    edited 2006-11-24 18:15
    matts persic,

    Capacitance sensors have a problem with "open" humidity (eventually). Float switches for the brewing chamber are my choice.

    How about a small load cell for the cup receiving the hot beverage?. Incorperate a "tare" function, and a full (grams or ounces) function.

    Tommy

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    Tommy, I know it wasn't designed to·x, but can you make it·do x·anyway?

    ·
  • Tracy AllenTracy Allen Posts: 6,664
    edited 2006-11-24 18:47
    For the cup, maybe light could reflect at an angle off the surface of the tea when the cup is full. Unless someone puts on a short cup....? Or a thermistor could point toward the side of the (paper?) cup and detect the heat of the tea

    For the tank, I'd look at the qprox dual-level sensor, too. The two levels are set by disks or spirals made of insulated wire, so the levels are quite reliable even with contamination buildup.

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    Tracy Allen
    www.emesystems.com
  • LSBLSB Posts: 175
    edited 2006-11-24 23:02
    Might also consider weight... Flexiforce make a 0-1 pound sensor similar to the 0-100 pound version that Parallax stocks. I think they only sell in a four pack, but other students may be able to incorporate it in their design (whatever the project), or perhaps there are takers here; I'd send you a check for one. email or PM if this is the route you decide to take...

    Mark
  • Kevin WoodKevin Wood Posts: 1,266
    edited 2006-11-25 01:55
    Is measuring fluid levels a design requirement?

    If not, you could remove the complexity by using a fixed capacity on both ends of the design.

    However, if you need to measure levels, you could use glass containers and photosensors in a linear array to detect levels.

    Using a typical coffee maker as an example, you could mount photosensors vertically, embedded in the chassis behind the coffee pot. The fluid level would block the sensors, which you would read for your level.

    You may be able to do the same thing with the heating chamber, or possibly use a similar array of humidity sensors calibrated for liquid volume.
  • Martin HebelMartin Hebel Posts: 1,239
    edited 2006-11-25 02:07
    How about putting a small pipe to the bottom of the pot and using a pressure sensor to detect the level based upon the pressure exerted by the column of water?· We've done this in my 2nd year technical electronics program with level control to 0.5 inches without little work.· You may have to search a bit since there will be some stream issues, but do-able I would think.

    Martin Hebel
    Southern Illinios University Carbondale
    Electronic Systems Tehcnologies


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    Martin Hebel
    StampPlot - Graphical Data Acquisition and Control
    AppBee -·2.4GHz Wireless Adapters & transceivers·for the BASIC Stamp & Other controllers·
  • matts persicmatts persic Posts: 3
    edited 2006-11-25 06:48
    Thanks for the ideas!

    I like the idea for a sight glass coming off of the brewing reservoir and then using a photosensor. That would take care of the boiling water. I think the float, while reliable, might be difficult for me to layout/install to prevent it from getting in the way of the tea bag and robotic arm activity.

    FlexiForce and weight sounds good for the tea cup and I have a sensor (but no time yet to experiment), though I am worried about the accuracy and overfilling, though I suppose I could just restrict the weight of the cup (they will be ceramic mugs).

    I really like the www.qprox.com capacitance idea (though I am using a metal container, I could apply it to the sight glass). I have never worked with them so it would be educational! Plus they have related ideas/posts on their forum.

    Thanks again! I never really used a forum before - this has been a great and helpful experience! Thanks!

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    Matts Persic

    14231 Komedal Rd., NE
    Bainbridge Island, WA 98110
    United States

    mattspersic@comcast.net

    +1 206 931-1653 USA
    +44 (77) 93827641 UK
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