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BS2 Measuring temperature? — Parallax Forums

BS2 Measuring temperature?

Brian D.Brian D. Posts: 12
edited 2011-07-23 17:37 in General Discussion
Howdy

Working on a new project - Fully automated birdbath! (complete with drain & fill valves - already ran the waterline into the back yard) Want to incorporate an air temperature sensor to increase the bird bath's refresh rate when it gets hotter outside.

I have the parallax AD592 temperature probe. The probe ohms out at around 1 meg ohms, and this is it's operating range. I don't believe this will work well with an RC time circuit because the resistance is too high. Anyone successfully used this probe with a BS2, and example circuit? Thanks

Brian

Comments

  • RDL2004RDL2004 Posts: 2,554
    edited 2011-07-23 07:02
    It's more accurate to use an ADC but Tracy Allen has some info on how to use RC time.

    http://www.emesystems.com/OL2heat.htm#AD590
  • Tracy AllenTracy Allen Posts: 6,666
    edited 2011-07-23 09:16
    The AD592 is a not a resistor. It is an integrated circuit that regulates the current flowing through itself. 1 microamp per Kelvin, so at 27 degrees Celsius it produces 300 microamps. Details in the reference Rick posted, or in the text for Applied Sensors of Stamp-in-class.
  • WBA ConsultingWBA Consulting Posts: 2,935
    edited 2011-07-23 09:23
    The Analog Devices AD592 datasheet has more information as to how to use it and some example circuits (IE: pg 5) that should enable you to use it with an RCTime circuit
  • ercoerco Posts: 20,259
    edited 2011-07-23 10:07
    These days, everyone is in love with digital temperature (and light) measurement. I don't get it. May I humbly suggest that old-school analog thermistors and photocells/phototransistors are cheap, plentiful, and work great with RCtime. So you have to calibrate a few data points. Is that such a big deal?

    And while I'm up on my soap box, they AIN'T LDRs! Enough acronyms already, my BFFs. They have always been (and shall forever continue to be) photocells. CdS still rocks, RoHS-compliant or not.
  • piguy101piguy101 Posts: 248
    edited 2011-07-23 10:45
    I have to agree with erco on this one. I once built a thermometer with the BS2 and a NTC thermistor. Take out the data sheet, graph it on excel, create an equation for the graph, create an equation for RC time, make the BS2 do all that and I got about a 0.5F accuracy with only days of work. It is that simple.
  • ercoerco Posts: 20,259
    edited 2011-07-23 11:13
    Thanks for backing me up, piguy101.

    While we have the analog podium, vacuum tubes & nixie tubes are the ONLY way to go. Who's with me?
  • Brian D.Brian D. Posts: 12
    edited 2011-07-23 12:50
    Ah thanks everyone - I thought it was basically just a thermistor. I plan a video for the completed Birdbath - throw it up here in a couple of weeks. I finally have the drain & fill valves working flawlessly.
  • $WMc%$WMc% Posts: 1,884
    edited 2011-07-23 13:50
    RadioShack sells a nice little Thermistor.
    '
    I have used it many times with the RCTIME statement.
    '
    This will save you the wait on shipping.
  • ercoerco Posts: 20,259
    edited 2011-07-23 17:37
    The Shack USED to carry a nice little thermistor, but my old friend 271-0110 is now long gone and quite hard to find. I have a few spares.

    http://support.radioshack.com/support_supplies/31961.htm

    Fortunately, similar garden variety thermistors are easily found in most decenet electronics shops, and even at the Goldmine! http://www.goldmine-elec-products.com/prodinfo.asp?number=G2005

    Thermistor alarm at http://www.goldmine-elec-products.com/prodinfo.asp?number=C6908
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