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Hack Basement Watchdog Water Alarm

Discussion in 'General Electronics Discussion' started by backporch, Feb 1, 2016.

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  1. backporch

    backporch

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    Feb 1, 2016
    Hello,

    I am brand new to this forum and also just starting to learn about electronics.

    My current project is to take the Basement Watchdog manufactured by Glentronics and update it to have four wires coming from the case. Two would be DC Power in from a plug, I was going to use my home alarm's 12V to replace the 9V battery and another two wires to connect to a relay that will signal my home alarm that the watchdog has gone off. I thought this would be a piece of cake, but I got nowhere with it.

    I would like to keep the current siren and attach a wire to whatever pin is energized to 9v when the siren is blaring. On exposing the circuit board, I see the siren is connected by three pins. All of them are at 6.5 V or thereabout when the siren is silent. As best I can tell it is attached to a chip that works as a amplifier. When you put the sensors in water, a small voltage appears at a transistor that opens and completes the circuit so the siren can sound. I tried to connect a additional transistor in the same way and it rendered the sirens inoperable.

    I apologize that this doesn't make much sense. I can include pictures of the circuit board.

    Appreciate the help.
     
  2. Gryd3

    Gryd3

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    Jun 25, 2014
    Yes, please include the pic of the circuit board. As clear as possible.
    (No flash, straight on the front and back of the board)

    There may be multiple points you can inject an additional wire to use as an output to tie into your home alarm.
    Please note that you may be charged or fined if the home alarm goes off and dials emergency services on your behalf. So please me diligent in ensuring that whatever your method, it works as designed and reliably.
     
  3. backporch

    backporch

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    Feb 1, 2016
    Thanks for the help. I appreciate the words of warning. My home alarm is not connected to central monitoring. Only I get a notification myself.

    If anyone has questions or would like measurements of any specific point, please let me know. The bottom view of the board is flipped so it matches the top view. Thought that might be easier to follow.

    Not shown well is the picture is a diode under the buzzer's top right. It is to the left of the two capacitors. The diode's stripe is on the lower part away from the edge of the board.

    Even if someone has a hunch, I can try it out with a few components and a breadboard.
     

    Attached Files:

  4. ChosunOne

    ChosunOne

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    Jun 20, 2010
    Backporch, what's the manufacturer and model number of your home alarm control panel? The home alarm control panels I'm familiar with support environmental sensors like your water sensor without the need to hack them through a relay.
     
  5. 73's de Edd

    73's de Edd

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    Aug 21, 2015
    Sir backporch . . . . . .

    If we do have to further analyze the board.

    You got answers . . .? . . . . . . .we gots questions.

    Top right corner, foil side of board, 9 VDC from batt comes in and initially gets a ceramic "cleansing" capacitor, along with power then passing on to what probably is a varistor, give us its numbering, then the third connection is probably being a 1N 4xxx series of diode with its polarity band on the end that goes down to the pin #1 of the MYSTERY 14 pin IC for power insertion . . .give us all of that IC's markings.


    Flip to the other component side of the PCB now.
    Bottom left corner FET is associated with the "wet" aspect sensing of the unit.

    Me thinks that shifted coloragraphy has altered the perceived R1 value . . . .reading nowto my eyes as red-red-black 22 ohms, confirm that third color band is probably being a green band or remotely possible . . .a blue band..

    Also give the numbering on the Q1 FET.

    Seems like R2 is a yellow/violet/yellow 470K with possibly R4 at the top being the same value, and with R5, having being flipped 180 degrees, it might ALSO be the same value.

    So you wants 12VDC coming in and being regulated on down to 9 VDC , serving for the boards uninterrupted power supply and
    adjunct circuity, triggered by the piezo alarm will additionally be giving a totally isolated ,normally open switch contact, that closes during piezo alarm activation.

    Thasssit . . . .

    73's de Edd
     
    Last edited by a moderator: Feb 6, 2016
  6. backporch

    backporch

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    Feb 1, 2016
    Thanks to all who read and commented. This is a great forum.

    My alarm panel is a Candian made Paradox, Spectra model 1728ex from 2002. Not sure what it can accept in terms of sensors. My plan is to actually hook up the alarm trigger to a surveillance system made by Q-See in California. This system can send me a picture when an alarm is triggered, so I will probably hookup a camera focused on my sump pit with a dim light shining on it. A picture with no light means the circuit with the light and sump pump has tripped, a picture with a full sump pump would indicate a pump problem. Of course, complete loss of power is a different issue.

    The circuit board has the following parts.

    IC Markings ( Texas Instruments ) 2 lines of text.
    Upper line 4BA50GK (E4 in superscript above a bar)
    Lower line CD4o69UBE underneath

    There are 4 resistors.

    R1 Red,Red,Green, Gold
    R2 Yellow, Violet, Yellow Gold
    R3 Red, Red, Yellow, Gold
    R4 same as R2

    The transistor has markings 2N 7000 -F12

    Please let me know if I left anything out.
     
  7. AnalogKid

    AnalogKid

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    Jun 10, 2015
    When there is a water event, does the alarm beep intermittently or make a continuous tone? If it beeps, then:

    The TI chip is a hex inverter. Multiple gates are connected in parallel to increase the current drive capability into the piezo beeper. This forma a crystal oscillator, with the piezo element as the crystal, and it oscillates at the transducer's natural resonant frequency for maximum efficiency and volume. One possible circuit is attached. Dave first published it in 1993 in Electronic Design.

    The water sensor input and a resistor form a voltage divider, and the FET's threshold voltage acts as a crude voltage comparator to enable the oscillator. The good news is that the FET and the 4069 can operate safely on voltages up to +15 Vdc, so you do not have to externally regulate the 12 V power source down to 9 V. The bad news is that the FET is not providing a clean "full-on" or "full-off" signal at its drain, so driving even a small relay coil might be a problem.

    ak
    beeper.gif
     
    Gryd3 likes this.
  8. backporch

    backporch

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    Feb 1, 2016
    Hello AnalogKid,

    The buzzer sounds continuously. I scanned over what you sent and I need to look a little deeper to try and understand most of the concepts.

    What I did take away immediately is that I may be able to run this directly on 12V, which makes things a little easier and that there might not be a clear threshold between on and off for this setup. I can verify that the product works really well that dry is silent and submerged is very loud. I can also verify that if I short the sensor with my fingers I can sometimes get a muted tone. I don't expect too many "false alarms" where the buzzer goes off at a low tone and triggers my relay once installed in the correct location.

    Thanks
     
  9. AnalogKid

    AnalogKid

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    Jun 10, 2015
    Note that the 2N7000 is installed backwards according to the legend. This is not a problem because the legend is wrong. Also, the FET is not doing a "normal" thing. My snap judgement in post #7 is incorrect.

    The FET is installed between the 4069's Vss pin and circuit GND. It does not gate the oscillator on and of in the normal way. It does it by completing the chip's connection to the battery. It is a power switch, not a signal driver. Cute.

    This is a good thing. It means that you might get away with connecting your (small) relay coil (with a transient suppression diode (!!!)) across the chip's pins 1 and 14.

    What is the black blob next to C1? Also, can you post another top side pic rotated 180 deg from the first one so we can see what's on that side of the beeper?

    ak
     
    Last edited: Feb 3, 2016
  10. backporch

    backporch

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    Feb 1, 2016
    AnalogKid,

    Thanks for the further analysis. I came across a datasheet last week. I will check it out again for the pin numbers and give it a try. The diode is to protect the electronics from the coil in the relay? I had also read about that but wanted to make sure.

    I will give it a try tonight and post the results !!
     
  11. 73's de Edd

    73's de Edd

    2,939
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    Aug 21, 2015
    Sir back porch . . . . . . .

    . . . . . . frontporch here . . . . . . . now, how comes we haven't run into each others before ?

    Working with your supplied info and seeing that you seem to be a rolled up sleeves kind of guy . . ..

    Here goes:

    That units design is really a gnats stomping his foot . . . . . power conserving type of device.

    Good to see that its principal component is a CMOS hex inverter/buffer chip, I marked its sections in on the mortified photo below.
    There are three sections in series BUT they are paralleling all three also, in order to heft up the power handling capabilities of the sets.
    This IC is being the driver for the piezo alarm, with one sneaky little procedure used to reduce power consumption to almost ZERO from the battery.
    The alarm sound creation portion stands all complete and ready to operate , with the EXCEPTION being that the I.C. pin 7 HAS to get to a ground connection.
    Take note of that pin and its connective foil path to the left that ends up at the FET.
    What needs to happen now is for the sump pump detection action to activate the gate of the FET and the unit conducts fully and thereby provides that grounding action for pin 7 and ye olde alarm goes OFFFFFFFF.

    Now in fulfilling your mentioned desires of activation of a completely isolated relay contact, via this alarm action.

    The little 9 Volt relay shown has a coil resistance value in the order of 75----115 ohms and considering that consumption, the Zener and its input current limiting resistor will allow some headroom above that relays need.

    If you would desire even less coil current consumption, do a transition to a reed relay, their coils are usually 500 ohms, but rated at 5VDC.
    Therefore figure on a series dropping resistor on the 9 V supply side to drop 9 down to 5V.

    Since you are free of the battery the power consumption factor seems irrelevant now.

    The last unknown factor is the fact that the IC is floating and not knowing its "bleed thru" voltage to the resistor at the base of the 2N2222.
    That is where you get to experiment in its value, too high of a resistance and not enought drive to the 2222 base, or too low of a value an it may load down the IC and affect its operation.
    There are also three degress of power between the inverters stages , the cleanest and most processed output would be at pin 8, with an intermediate at pin10, and the least processed is at pin 12 where it is akin to a comparator stage, in establishing initial switching thresholds.
    Experiment with both 2222 input isloation resistance and the stage that you acquire base drive from.

    Seek and ye shall find . . . . . .that optimum value.

    Also, there might be a need of hanging some few microfarads from an electrolytic cap from the collector to ground on the 2222.

    As a back-back up . . . .. one could also consider use of a FET for the relay driver


    Techno Referencing Photo:

    [​IMG]

    73's de Edd

    POST . . . .(mortem)

    I poked this up last night and you were progressed only up to post # 6.
    My image hosting site was sluggish and I gave up on the picture 'til today.
    In proofing out my post now, I see that there had been some interim activity.
    You can still see the proof of concept mark up, but the tack in of a relay
    (particularly the reed type, with a dropping resistor) from pins 7 to 14 might
    also provide an interfacing.
    As was so suggested by our honorable and esteemed A.K.

    .
     
    Last edited by a moderator: Feb 6, 2016
  12. backporch

    backporch

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    Feb 1, 2016
    73 and AK,

    You have given me all the information I need to get this done and I appreciate it greatly. I am going to print this out and slowly read and attempt to understand all the information. I may not wire this up tonight, but I will work on this in the next day or so and get back to the forum with results or maybe a follow on question.

    They really should have offered this product. Commercial ones sell for a whole lot of cash.
     
  13. backporch

    backporch

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    Feb 1, 2016
    I attempted to wire up the circuit using the excellent guidance you provided, but the results were not what I had hoped they would be. In theory I think I kind of get what is going on but I think I am falling short on some basics. The relay was energized regardless of whether the connection to the transistor base was even attached to the IC.

    I have what looks like transistors, several types, markings s8050-D331, S8550-D331, P2N2-222A-E35 and one that is barely legible. maybe twp36gz1444005582. I used the P2N2-222A. I guess I don't understand the transistor. Strange thing was I was able to pass 12v through a 10k resistor and then the collector and emitter with the base connected to nothing and light up an LED. I thought this would not work. l could light up the LED regardless of which two legs of the resistor I chose to traverse. I was under the impression that collector and emitter would be disabled somewhat until there was a smalll voltage at the base.

    Given that my transistor allowed the circuit above to be grounded it makes sense that the relay tripped regardless of whether or not the base was connected to the IC pin and of course whether or not the buzzer was energized.

    The most surprising thing is that the water alarm still works after all my messing with it.

    I could use a dummy slap or something. Thanks.
     
  14. AnalogKid

    AnalogKid

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    Jun 10, 2015
    What is your relay manufacturer/part number? Do you know its coil voltage rating, resistance, etc?
     
  15. 73's de Edd

    73's de Edd

    2,939
    1,246
    Aug 21, 2015
    Sir backporch . . . . .


    The last part number you have given is probably a TMP 36 and is a temp sensor IC, in what you might think is a transistor, due to its TO-92 casing..

    Either the PN2222 or P2N2222 are proper parts UNLESS you made a mistake on its collector-base- emitter connections, or if it is leaky or shorted.
    Take vewy-vewy-vewy careful note of that PREFIX as the collectors and emitters swap positions.
    Its never a problem for me, as I am always using 50 year old surplus units in a metal case .
    Refer to the right top corner info on this reference below on the basing/number variants.

    https://en.wikipedia.org/wiki/2N2222

    The S8050 also should be a proper part .

    With the unit wired as shown, the relay shoud not be closed IF the base resistor is floating and free.
    To positively confirm, connect the base resistor to the transistors emitter/ or / ground and expect no closed relay.
    If its closed, the transistor must be bad from collector to emitter.

    I also am waiting for the relay / type / number /specs.


    73's de Edd
     
    Last edited by a moderator: Feb 6, 2016
  16. backporch

    backporch

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    Feb 1, 2016
  17. backporch

    backporch

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    Feb 1, 2016
    Reading some of the other info. I guess I overlooked the P2N and the pins being reversed. That would make a difference !
     
  18. 73's de Edd

    73's de Edd

    2,939
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    Aug 21, 2015
    Sir "back"porch . . . . .


    Sooooooooo it looks like you just might have "warred" that transistor in "back" wards.

    That 12 VDC relays lower pull in spec is iffy, so try the 9 V battery and ohm out its relay contacts to see if it is reliably switching at that low level.
    It's for sure that it is holding . . . . . at that low .65 VDC drop out spec.
    I'm deaf-dumb and blind at this end, so is this alarm actually an original factory installed portion of your sump pump that the manufacturer incorporated
    in its construction ?
    The other question would be if the sump pump utilizes a float switch(es) that is/are shorting on water rise and the black line pair coming to the board detects a shorted (0 ohms)
    switch closure . . .OR . . . is the detection mode a wet conductive resistance type of detection.
    (Assuredly, being the latter, since you mentioned . . . . . "I can also verify that if I short the sensor with my fingers I can sometimes get a muted tone."

    If water detection is being the latter, running the board at a full 12VDC power level might unduly "oversensitize" that type of detection system, without compensating for it in its design.
    The simplest manner, being the install of that 9V zener over PAST the first resistor coming over from the main popwer supply line towards the sensor circuitry.
    That way the detection circuitry still runs at its designed 9VDC and the 12VDC can supply the IC and either the relay driver transistor+ relay or just the 12 vdc relay across the
    IC power pins as A.K. had chimed in with.


    73's de Edd
     
    Last edited by a moderator: Feb 6, 2016
  19. backporch

    backporch

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    0
    Feb 1, 2016
    I wired up the transistor again and it makes more sense now. The collector and emitter are isolated from each other until a voltage is applied at the base. Nice.

    The sensor consists of two metallic disks separated about an inch apart on a piece of plastic. The buzzer will sound when I short the sensor pads with a finger.

    My problem now appears that whenever the sensor is plugged into the 9v source, but no actually going off, all of the 14 pins of the IC are between 6 and 8 V. I probably should have measured these right from the start. Was the expectation that they would be at 0V until the alarm was tripped?

    I suspect that once working, this sensor will be tripped very infrequently. A splash of water will allow a picture to be sent in an email and as long as the alarm's battery has power, the siren will blare. Much longer than the 3hr life of a 9V battery with the siren activated.
     
  20. AnalogKid

    AnalogKid

    2,408
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    Jun 10, 2015
    Not an actual problem. Remember that when the sensor is not tripped, the chip has no GND connection because the FET is like an open switch (or a very high value resistor). The chip is essentially off, and floating above ground. In fact, it is the input impedance of the meter that is making any kind of reading possible; the meter is completing the chip's power path to GND (very poorly).

    ak
     
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