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Freezer Current Safety Indicator?

Discussion in 'Electronic Design' started by Jones, Apr 20, 2007.

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  1. Jones

    Jones Guest

    Hello, all,

    I have a chest freezer that I keep in an outbuilding.

    On at least one occasion, for whatever reason (lightning?), this
    freezer has thrown a breaker, [email protected] out (without us knowing it) and
    stunk up the garage with rotten food and bait.

    (We only rarely open the freezer, so it took a while for us to realize
    that it had thrown a breaker and was powered down.)

    Does anyone know of a simple way I could rig something up to show when
    the freezer stops pulling current for more than, say, a day or two?

    At first I was thinking an ammeter would work, but obviously, the
    freezer isn't running ALL the time, so the lack of current wouldn't
    necessarily indicate a problem.

    What I would like is a prepared solution for this, perhaps a gizmo that
    would go between the freezer and the 110V outlet that would LIGHT UP or
    SOUND A SIREN when the freezer stopped drawing current for more than a
    specified time.

    Does anyone know of a device that would work for this purpose, or of a
    simple way to make one (I can solder, but beyond that, I'm pretty
    clueless, so be gentle!)?

    Thanks for any clues,

    Jones.
     
  2. Perhaps the simplest (and better) way is use a temperature sensor.
    You can use a simpel silicon diode, at the input of an opamp,
    that triggers a beeper for example (via a wire in the house).

    I dunno if you can make that, if you think you can I can post a diagram.
    (run from an AC adapter).

    Perhaps complete remote temp sensors exists that have an alarm?

    I would not bother measuring current, as that is no indication you did not
    leave the door open for example.
    Always measure what you want to know, not some related value.
     
  3. Jim Thompson

    Jim Thompson Guest

    Make sure the breaker is NOT GCFI. GCFI's are NOT recommended fro
    freezers, refrigerators, etc.

    ...Jim Thompson
     
  4. colin

    colin Guest

    You can buy fridge alarms.

    Colin =^.^=
     
  5. A cheap thermometer with alarm and wired sensor, and extend the wire.
    e.g.
    http://www.maplin.co.uk/module.aspx?ModuleNo=36131&doy=20m4
     
  6. Some times old fridges have motors, whost startup current peaks a causes the
    breaker to kick in.


    **** Disclaimer ****
    *****If you are not experienced in electronics AND electrical safety then
    do not attempt these suggestions *****

    **** Tinkering 240V ac / 110Vac mains voltage can be hazardous to your
    health! ****

    **** If any of this is unfamiliar then seek electrical professional help
    before attempting any thing ***
    Now the disclaimer is out of the way.

    In stores , most freezers are fitted with over complicated alarms...They
    have to meet food regulations.

    1. Thermostat's
    A temp sensor - hooked up outside to detection threshold device or circuit,
    hooked up to a buzzer.

    I remember when I was 10years old (some time ago) there are some temperature
    switches
    that you could connect to a battery and a buzzer... depending on your
    electrical / electronic skill.
    (backup battery and plug pack used as the power source)

    Oh, yeah, I remember now - they are call thermostat's here's the 1st
    search on google.
    http://www.thermodisc.com/productdetail.asp?ProductID=2

    If you are building only a few there will be other places that sell small
    volumes.
    Make sure the wires don't cause a poor seal on the door.
    And there is no mucking around with the Hazardous mains (240/110V ac)
    voltage.

    2. Parallel Voltage measurement.
    The mains failure might be a circuit beaker or mains power as you suggested.

    This idea is cheeky but effective.... because is also not connecting
    "directly" with
    mains high voltage (240V/ 110V) (which is hazardous to your health)

    - Put the fridge and a low voltage AC adapter in to the same power board or
    2way power board.
    something like this one (but for your country) http://tinyurl.com/2jjbbe
    - Use the output of the AC adapter and connect to the coil terminals of
    relay
    (same voltage as the AC adapter's --> DC output)
    - Wire the relay's Normally Closed(NC) terminal to the + side of a battery
    - Wire the relay Common (C) terminal to a + side of DC buzzer same voltage
    as the battery
    - Wire the -side of the battery to the -side of the DC buzzer.

    When the mains power is on the AC adapters DC output keeps the relay
    contacts open between
    (C) and (NC), the battery is off, not drawing any current.

    When the mains power is off, the relay is de-energised and the (C) and (NC)
    contacts connect causing the buzzer to go on.

    It's cheeky because the when the power is off the buzzer will be on.. so
    it's a sort of built in backup.


    2. AC Mains Current detection
    *** Dangerous unless you know what you are doing ***
    I can see where you are going buy trying to measure the current, so nothing
    is connected directly to the fridge....
    but it will need battery backup if your whole house/building power fails.

    Suffice to say you can use a type of current transformer.... sorry no more
    details without knowing your electrical safety experience.




    Joe
     
  7. GregS

    GregS Guest

    Alarms are simple. I also have made alarms with battery backup in
    case the power is off. Its to warn of meltdown. Most common ones
    now are batery opperated.
    there is a device I have seen on the market that I thought was very cheap
    which monitors AC current but no alarm. Probably usefull for determing
    startup current. Radio Shack?

    greg
     
  8. Or if you have money google temp alarm or other close key words and you
    can buy one off the shelf.

    Joe
     
  9. Eeyore

    Eeyore Guest

  10. You can buy alarms that react to the temperature in the freezer. You
    could also (instantly) detect the power failure at the outlet, for
    example with a beeper, battery and a mains voltage AC relay (use a
    normally closed contact).

    But if your freezer is causing the breaker to trip there's something
    wrong with the freezer and/or the breaker.



    Best regards,
    Spehro Pefhany
     
  11. GregS

    GregS Guest

    Most do have motors.

    Around other parts, some people will plug in two or three coolers into one breaker.
    Most of the time two will work OK on a 20 amp breaker, but still risky.
    Three definately no. Most cruise at 5-8 amps, but at start up can triple or more.
    Every once in a while they all try to come on at the same time.

    greg
     
  12. D from BC

    D from BC Guest

    You rarely open it.???
    Maybe get rid of the fridge...
    Unless you like eating freezer burnt burger patties from 1990...
    D from BC
     
  13. Rich Grise

    Rich Grise Guest

    The simplest would be a normally-closed Klixon, like one of these:
    http://www.sensata.com/products/controls/ptherm-6786.htm
    and a 6V lantern-type battery but with screw posts, some wire,
    and a Sonalert:
    http://www.mallory-sonalert.com/2_2_1.htm

    Good Luck!
    Rich
     
  14. GregS

    GregS Guest

    I just wish they would put clocks in them fridges and allow one to set the defrost
    time. I alwas detected when it was after a defrost by how soft the ice cream was.
    happens with all of them. I measure the temps over several days. After a 45 minuite
    defroast cycle it gets up to 26 degrees for a short interval. If one opens
    the door on a hot warm summer day, it goes up######. The refridgerator section
    actually has better temperatur control, but still if you open the door your
    in trouble.

    They have one at Best Buy with a TV.

    greg
     
  15. Jim Thompson

    Jim Thompson Guest

    The best freezers for long term storage DO NOT have an auto-defrost
    cycle. That's how you get freezer-burned food.

    ...Jim Thompson
     
  16. GregS

    GregS Guest

    We used to have a chest freezer. I was never was a fan of frost free.

    greg
     
  17. I have sad experience with that. When we moved, the house came with
    the existing refrigerator, so we moved it to the garage as a beer
    cooler and freezer overflow. That garage outlet is on the same
    circuit as the backyard outdoor outlet, so it is GFCI-protected. My
    son fooling around with the outdoor outlet (sticking a weedpuller in
    it) triggered the GFCI circuit. We found out several days later after
    the frozen fish had thawed.

    I contemplated dumping the beer along with the fish, but a few short
    taste tests proved that it was not completely spoiled.
     
  18. Jones

    Jones Guest

    Gosh, I had no expectation of such a wealth of replies...thank you,
    everyone! I need to chew on all of this!

    Many thanks...I will probably reply with further questions.

    Jones.
     
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