Pet water dish alarm

Discussion in 'The Projects Forum' started by Wendy, May 23, 2015.

  1. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    I use a watering system with a 3 gallon jug attached. It's convienent, except I don't always notice the pooch is out of water in a timely manner. So I sketched this up for a weekend project.

    Pet Water Dish Alarm.png

    Just thought I'd put this out there.
     
    Last edited: May 23, 2015
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    What does the croc clips sense ?
     
  3. Dodgydave

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    Jun 22, 2012
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    Don't see why you need Q2, just put the collector of Q1 to the 555,

    Or use a pull up resistor on pin 4, and use the crocodile clips on pin 4 and pin 1, then when the water is low it buzzes, you may need to put the buzzer and led to pins 1,3.
     
  4. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    Two words:

    Battery life

    By using a really high gain transistor I can raise the resistance of all the parts, Never having experimented with pin 4 upper limits on resistance I chose what works. Speaking of which, guess I need to up R3 to 1MΩ.

    The alarm sounds 1/2 seconds out of 5 minutes, enough to be noticed.

    The alligator clips are the sense input.
     
  5. Alec_t

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    Sep 17, 2013
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    With such a small current through the clips, hopefully electrolytic corrosion won't be too bad. If it proves bothersome you might want to consider energising them with AC rather than DC.
     
  6. Wendy

    Thread Starter Moderator

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    We shall see. :)

    Thanks.
     
  7. R!f@@

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    What is the sensor ?
     
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  8. Dodgydave

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    Jun 22, 2012
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    the Reset minimum voltage level is 1V, so anything above 1 V and the chip will run ok, below 1V it resets.
     
  9. Wendy

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    Mar 24, 2008
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    It senses whether water is between them, conducting. DI water is an insulator, but water in the wild usually conducts quite well.

    On a conventional 555 it is .7 volts, but that doesn't tell me the input resistance of pin 4 on a CMOS 555, or what the maximum reliable resistance to use for the pull up. I agree I could have done it this way (with other changes), but this is the way I choose to do it. My confidence is high this will work the first time, and will only need new batteries every 6months to a year.
     
  10. RichardO

    Well-Known Member

    May 4, 2013
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    I would turn on and off your circuit using MOS-FET. Use a very high value resistor to hold the FET off. Put the electrodes from battery + to the FET gate.

    Doing it this way, the circuit draws absolutely no power when the electrodes are dry.
     
  11. ebeowulf17

    Active Member

    Aug 12, 2014
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    Isn't that backwards? When the electrodes are dry, you need it to sound the alert. It can't be zero power consumption when the electrodes are dry.
     
  12. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    Agreed, which is why it is designed the way it is. This is not a water alarm, but a lack of water alarm.

    I'm going to do something different and build this dead bug style on the back of the sonalert.
     
  13. flat5

    Active Member

    Nov 13, 2008
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    Please post a picture when ready.
     
  14. ScottWang

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    Aug 23, 2012
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    If you considering the electrolytic corrosion of alligator clips then maybe you could find some steel chopsticks or something similar.
     
  15. flat5

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    Nov 13, 2008
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    Very large paper clips
     
  16. KMoffett

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    Dec 19, 2007
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    For electrodes that are going to be submerged and conducting most of the time, use AC drive and demodulation, and stainless steel electrodes. TIG welding rods, or SS wire from the hardware store. Keep the clips out of the water. This can be done with CD4093 gates. Maybe with a 556.

    Ken
     
  17. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    Naw, its complex enough, and paperclips are cheap.

    Less than 3 microamps isn't much current.
     
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