Open door indicator on refrigerator

Discussion in 'General Electronics Chat' started by bbqbrisket, Oct 9, 2017.

  1. bbqbrisket

    Thread Starter New Member

    Oct 9, 2017
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    device: Thermador refrigerator
    subj: Open door indicator with light and sound

    Q: Is it common to be able to adjust an open-door indicator, or are they usually fixed?
     
  2. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    The ones that I’m familiar with have a built-in limit switch of molded plastic and are not adjustable by normal means. One could get creative however by adding or subtracting material to “adjust”.
     
  3. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Years ago I saw a circuit that was a simple timer alarm activated when the refrigerator's light was on (hence the door was open), and went dormant when it was off. It was fully adjustable on sensitivity and time lapse, and it had the advantage of its not needing to be connected to anything in the fridge.
     
  4. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Many refrigerators use mechanical switches as @djsfantasi said.
    Those will switch the light of the fridge and sometimes start a timer that will sound after some time.
    Also a magnet and reed contact may be used.
    In that case there is no visible switch.

    Bertus
     
  5. wayneh

    Expert

    Sep 9, 2010
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    I have never seen one that was meant to be adjustable.
     
  6. Reloadron

    Distinguished Member

    Jan 15, 2015
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    Did you ever wonder if the light in the refrigerator really goes off when you close the door? :)

    We have an older Whirlpool and it uses a mechanical switch in the door frame and an incandescent bulb. The freezer also Whirlpool, uses a mechanical switch but with really nice LED lighting. Adding an audible to either would be an easy enough task.

    Neither of mine are adjustable and I really see no need for an adjustable switch scheme.

    Ron
     
  7. MrAl

    AAC Fanatic!

    Jun 17, 2014
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    Hi,

    The only reason i can think of that might mean you'd have to adjust it is if there is something that changers over time. An example would be the switch button that wears out if it is rubbed or something.

    I made my own indicator, it's so very easy. It's just a magnetic reed switch with LED and battery holder mounted to the fridge and a small but strong magnet mounted to the door, all at the top of the door. When the door closes the reed switch either opens or closes (dont remember which) and the LED turns off.
    I dont remember if i used an inverting transistor stage or a magnet to bias the reed switch closed when the magnet is far away. The main thing is to keep the quiescent current low so the battery lasts a long time.
     
  8. philba

    Active Member

    Aug 17, 2017
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    I have a sub-zero with a plunger switch. There is a little plastic box that is mounted on the door - it pushes the plunger in. It's not adjustable but I guess one could mod it. However, when the door is closed, it's pretty much flush and I can't imagine wanting to adjust it out. The whole thing seems kind of brute force...

    This of course begs the question of what you are trying to do.

    By the way, my fridge and freezer have an open alarm that goes off after a few minutes. Unfortunately, it's so high pitched that it's above my age-attenuated hearing level.
     
    Tonyr1084 likes this.
  9. bbqbrisket

    Thread Starter New Member

    Oct 9, 2017
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    So, this door light/alarm are fully functional when the door is open enough that it triggers the light. What I have found out is that when the door is just slightly ajar and the inside light is not on, the door alarm door alarm does not work either.
    I see that it's operated by a spring-loaded rocker switch. So, I can only determine that the contact on the switch has too much space to allow the door to open a little before making contact. This small opening where the door is ajar, is not easily noticed because the doors look fully closed unless I get up very close to the door.
     
    Last edited: Oct 9, 2017
  10. Reloadron

    Distinguished Member

    Jan 15, 2015
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    While it may not be pretty but not necessarily ugly you could add an external magnetic reed switch and set it and adjust it accordingly. A few sheet metal screws and done. Connect a notification system of your choice. Magnet and switch combinations are available at any home improvement store. The same type used on windows with home security systems. They even come with double stick tape making for real easy installation. Used one on the trunk of my friends motorcycle to illuminate a LED strip and it worked out well, so well the last time I opened my trunk I thought I need to put one on my bike. :)

    Ron
     
  11. bbqbrisket

    Thread Starter New Member

    Oct 9, 2017
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    Fascinating....will look into this...thanks
     
  12. Reloadron

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    Here is an example of what I had in mind. You can likely find a cheaper flavor at Amazon or similar.

    Ron
     
  13. bbqbrisket

    Thread Starter New Member

    Oct 9, 2017
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    Thanks for sending that link so I know what to look for. I can see the installation but having difficulty visualizing what else ges connected to the sensor.
    thanks
     
  14. Reloadron

    Distinguished Member

    Jan 15, 2015
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    The magnetic reed switch is a NO (Normally Open) switch held closed by the magnet. These switches can normally directly drive any low current device or a transistor circuit to drive any higher current devices. The switch acts as your sensor and you can build just about anything of your choosing around that.For example a delay on make circuit where when the door is opened it triggers a circuit with a 30 second delay. If the door is not closed within 30 seconds you can have a visual or audible alarm. Really a matter of using the switch as a sensor to do whatever you want to do.

    Ron
     
  15. bbqbrisket

    Thread Starter New Member

    Oct 9, 2017
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    What size battery did you use?
     
  16. Tonyr1084

    Distinguished Member

    Sep 24, 2015
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    Long time ago I put a video camera on record and put it in the refrigerator just to see if it really did go off when the door was closed. Well, MINE went off when the door closed. Now, how about yours? How do YOU know?

    Modern fridges start a timer when the light is on. If the light is on longer than a preset period then the alarm will sound. My refrigerator sometimes turns the light off even when the door is not fully closed. I suppose I could probably just sand a little plastic off the switch button so that it takes a more fully closed door to shut the light off. But then I'd need a camera to record if the light goes off, otherwise I might not be able to sleep.
     
  17. KeepItSimpleStupid

    AAC Fanatic!

    Mar 4, 2014
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    "MY PLAN" is to use one of these http://www.essentracomponents.com/e...-catches/grabber-catches-side-mount-via-screw with the microswitch option. You can choose 3, 5 and 10 lbs of force. I used the catch version on a vacuum cleaner door and it worked out really nice and I plan to use it on another vacuum.

    The catches, pull the door closed so they should be perfect. Mounting, is the hard part. Plan is double stick tape, angles and flat stock

    It's for a freezer with no light. Difficult to see the door open. So, instead of a "door prop alarm". I'm planning to turn on a light that normally is turned on anyway when the freezer is open. I really would like a "comprehensive" alarm system with water and fridge/freezer alarm types.
    It's difficult to hear alarms in the basement when your upstairs.

    This one needs the effort.

    I did buy a $30.00 fridge alarm, but it has a few problems: You can't hear it. You can't see it. The suction cups don;t suck (don;t stick to the fridge)

    The thermister wire opens the gasket too much.
    I have a plan for the gasket problem. This stuff: https://www.superbrightleds.com/mor...ntent=NFLS10-FPW&utm_campaign=GoogleBaseChild

    It does tell you min/max and how long.

    I did some research and found this: http://dsigo.com/products/es4200-door-management-alarm/ Although i like it, it's way too expensive
     
  18. MrAl

    AAC Fanatic!

    Jun 17, 2014
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    Hi,

    I used three AAA type alkaline batteries in series. Normally i would have used three AA type alkalines but i happened to have a three AAA type battery holder laying around so i used that. The holder came out of an old LED flashlight that took three AAA batteries so i soldered leads to it and used it for the fridge.

    I did not mind using three AAA batteries this time because they only time they pump current is when the door is open, and it's usually only open for a few seconds in order to grab something inside or stick something inside and then it is closed again so the battery consumption is very low. That, and the fact that i only had to use a small 5mm white LED with max current 20ma and with that running at 10ma and the door open for short periods the three batteries last a long time. I could easily connect a buzzer too.

    As Ron said, you can bias a reed switch with a magnet to make it a normally closed version so when a second magnet (usually more powerful) comes close it disrupts the field of the first magnet and that opens the reed switch so the LED (and/or alarm) turns off and battery power goes down to almost nothing.

    A single transistor operated as inverter can also do the trick. Using a large base resistor like maybe 100k, when the door is closed the reed switch shorts out the base emitter so no current flows into the base and so the transistor stays off and so the LED stays off. When the door is opened the reed switch opens and the transistor sees base current, so it turns on and so does the LED. Simple circuit with one small transistor like 2N2222A and 100k base resistor maybe.
    With three AA or AAA batteries in series (so we dont need a boost circuit) and 100k the drain is 45ua so a 1000mAhr battery will last theoretically about two and a half years with the door shut, so maybe around a year or two with it being opened on a regular basis but not held open for long periods. That's approximate when using three AAA batteries, but three AA batteries would theoretically last twice as long.
    I must have done it that way or in a similar manner because i dont see any bias magnet near the reed switch.
     
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