1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Water Activated Alarm

Discussion in 'Electronic Projects' started by ElectroMaster, Jul 24, 2002.

Thread Status:
Not open for further replies.
  1. mudassir_semiconductor

    mudassir_semiconductor New Member

    Joined:
    May 16, 2006
    Messages:
    19
    Likes:
    0
    i made a automatic dam door control system using 555 timer but after that ...... i tought 0f using microcontroller and i did it ..... insted of all this u can only do by switch which will activate on any conduction ....... r ugetting me ..... this circuit is only for the understanding of transisters
     
  2. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,449
    Likes:
    937
    Location:
    Canada, of course!
    I added an LDR (light dependent resistor) and a 100k resistor. When it is light then the LDR is a low resistance and the 555 operates normally. When it is dark then the LDR is a high resistance and the 100k resistor causes the 555 to be reset. Try different values for the 100k resistor.

    This way, the battery is drained about 5ma when the sensor is wet in the dark. If the sensor is not wet then there is no drain.
     

    Attached Files:

  3. xl5

    xl5 Guest

    ONLINE
    Rain alarm.

    Hi Audioguru, thanks for posting the cct diagram with ldr i will now try the cct out on my breadboard. My very first project was a rain alarm back in 1972 it worked fine but if it was not switched off before retiring for the night sometimes it doubled as an extremely early alarm clock:D

    I have in the junk box many types of ldr's i will experiment with the resistor value.
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. umairtheonlyone

    umairtheonlyone New Member

    Joined:
    Jan 9, 2008
    Messages:
    4
    Likes:
    0

    Hey can anyone tell me about the speaker part I couldnot find it in the parts list in ewb
     
  6. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,449
    Likes:
    937
    Location:
    Canada, of course!
    The 555 has a max allowed output current of 200mA so it might be damaged if it directly drove an 8 ohm speaker when it has a 9V supply. Use an 18 ohm speaker or connect a 10 ohm resistor in series with an 8 ohm speaker.
     
  7. umairtheonlyone

    umairtheonlyone New Member

    Joined:
    Jan 9, 2008
    Messages:
    4
    Likes:
    0
    I cannot find the speaker anywhere I mean LS1 is not in my parts list in electronic work bench
     
  8. umairtheonlyone

    umairtheonlyone New Member

    Joined:
    Jan 9, 2008
    Messages:
    4
    Likes:
    0
    I cannot find LS1 anywhere in electronics work bench parts list
     
  9. Rachel49

    Rachel49 New Member

    Joined:
    Jan 14, 2008
    Messages:
    1
    Likes:
    0
    can i change BC109C to BC107?? plz help me...
     
    Last edited: Jan 17, 2008
  10. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

    Joined:
    Nov 17, 2003
    Messages:
    39,234
    Likes:
    641
    Location:
    Derbyshire, UK
    You could try, but a BC109 is a much higher gain device - so it depends how conductive the water is.
     
  11. RAKS

    RAKS New Member

    Joined:
    Jan 19, 2008
    Messages:
    11
    Likes:
    2
    Thanks for all.
     
  12. hirani

    hirani New Member

    Joined:
    Aug 14, 2006
    Messages:
    1
    Likes:
    0
    what is all this! a simple general purpose transistor like 2N2222 will do. water has a resistance of 2K/cm at 21 degrees celicius the base of the transistor can be baised using water resistance as a circuit completing resistor when contacted an CE voltage can be used to turn on any electrical appliance
     
  13. kentadams

    kentadams New Member

    Joined:
    Aug 18, 2008
    Messages:
    2
    Likes:
    0
    Ok, at the risk of making my first post here a stupid one, let me continue...

    I found this forum by searching for water alarms. I'm a total newcomer but why can't you simply have something like this?

    (excuse the child-like diagram) :)
     

    Attached Files:

  14. Willbe

    Willbe New Member

    Joined:
    Aug 16, 2008
    Messages:
    1,236
    Likes:
    7
    Location:
    MD
    If the audible alarm could sound using a few microamps or nanoamps, you could. The water doesn't conduct electricity that well.
    You might be able to use up to 50v through the water and have enough current left over to run some kind of alarm. These guys have some very sensitive alarms.
    www.hosfelt.com

    When I was a kid I used a salt water solution in a jar in series with 120vac in series with a small motor coupled to a fan blade. The salt water rheostat was used to slow down the fan so it wasn't noisy so I could sleep.

    By the time the water had boiled away the night air was cool enough so that I didn't need the fan to run.

    120vac, salt water solution, fan motor that didn't need much current, totally unsafe arrangement. This water alarm is quite different.
     
    Last edited: Aug 18, 2008
  15. kentadams

    kentadams New Member

    Joined:
    Aug 18, 2008
    Messages:
    2
    Likes:
    0
    Ahh gotcha. I was hoping that would trigger a little Piezo Buzzer.
     
  16. Willbe

    Willbe New Member

    Joined:
    Aug 16, 2008
    Messages:
    1,236
    Likes:
    7
    Location:
    MD
    Using a ρ = 0.1 megohm-cm value for the volume resistivity of tap water, if you had two one-square-cm plates one millimeter apart you'd get 10kΩ resistance between them.
    For a 9v battery, you need an alarm that runs on 9/10k = 1 mA.
    So for a 5 mA sonalert you'd need plates ~2 cm on a side.

    With several 9v batteries in series you just might do it.
     
    Last edited: Aug 18, 2008
  17. Willbe

    Willbe New Member

    Joined:
    Aug 16, 2008
    Messages:
    1,236
    Likes:
    7
    Location:
    MD
    previous post

    My landline phone Voc = 50vdc and Isc = 30 mA, which puts the Thevenin resistance at 50/0.03 = 1.7 kΩ.
    This resistance varies with the distance to the phone central office.

    The '99 NEC seems to say that 60vdc or less is "safe."

    So, this phone line voltage could be fed in series with water level detect electrodes to a Sonalert that is shunted by a Zener diode [to prevent excessive voltage across the sonalert].

    The only problem I see is that the surface tension of the water would prevent it from fully wetting a parallel-plate water detector that had narrow spacing, so you might need to work on a proper electrode configuration.

    You will probably need an on-off switch to regain control of your phone line if water is detected.
     
    Last edited: Aug 18, 2008
  18. georgie

    georgie New Member

    Joined:
    Aug 19, 2008
    Messages:
    7
    Likes:
    0
    i've alrdy try this circuit...it's easy if you follow the schematic diagram...by the way, u can also us 2n222 transistor...^^
     
  19. BCHurricane89

    BCHurricane89 New Member

    Joined:
    Aug 5, 2008
    Messages:
    32
    Likes:
    0
    Location:
    Battle Creek, MI
    Can anyone confirm that the 2N222 transistor works with this circuit, because I live in the U.S. and I cannot find the BC109C. Also, the probes or contacts for the water sensor, exactly what kind of wire should I get?

    EDIT: actually, I found an easier circuit, which should work pretty good:

    [​IMG]

    the two thick solid black things are the probes, or the water sensors
     
    Last edited: Aug 30, 2008
  20. georgie

    georgie New Member

    Joined:
    Aug 19, 2008
    Messages:
    7
    Likes:
    0
    Bc109c are switching type transistors. Actually you can also use the 1402c...or you can look up the other type on this transistor, it is ECG 123A for its replacement.^^
     
    Last edited: Aug 31, 2008
  21. Willbe

    Willbe New Member

    Joined:
    Aug 16, 2008
    Messages:
    1,236
    Likes:
    7
    Location:
    MD
    Stainless steel, but

    . . .I tried to measure the resistance across a 1 cm span of tap water with my B&K 391 DVM. I got -500k on the 20 MΩ scale so I assume the probe/water combo was generating voltage, but since the test probes were not dissimilar metals I really don't understand how this is possible.
    I don't think you'll have that problem with a circuit this simple.
     
    Last edited: Aug 31, 2008
Thread Status:
Not open for further replies.

Share This Page