Tuesday, July 13, 2010

Ailing Fridge and DIY Door-open Alert Unit

This article is about addressing a refrigerator that wasn't optimally turning on and off and a gadget that sounds off to help prevent at least one possible reason. Three possible common causes for a sickly refrigerator are a malfunctioning compressor, dirty coils, ice inside the freezer walls, or a combination. The refrigerator part of this article discusses assessing for and resolving for ice inside the walls—defrosting the entire unit and cleaning it during the process. The gadget part (DIY door-open alert unit) of this article discusses the project.

Ailing Fridge

I've occasionally taken out an armful of items, then forgotten to fully close the door. One problem has been the compressor overworking, causing icing up inside the freezer walls, resulting in appliance underperformance. Recent symptoms indicating all was not well included the following:

  • The fridge seemed to be running all the time instead of in on/off cycles.
  • Eggs toward the back of the fridge froze or partially froze.
  • Water pitchers occasionally wound up with shallow icy layers.
  • Fresh spinach leaves froze about the upper three leaf layers.

Tweaking refrigerator settings didn't seem to always resolve the problems. The longer-term process for resolution was to defrost the refrigerator/freezer, which included emptying it out and leaving the doors open for a couple of days, ensuring any possible ice in the walls would melt and the water drip away. The main sections of the process are total defrost preparation, defrosting, and cleaning.

Preparation for Total Defrost of the Refrigerator

  1. Over time, consume all freezer items.
  2. Over time, consume fridge items that needed refrigeration. If not consuming them all,
    1. Give them away.
    2. Throw them away.
    3. Obtain dry ice to store the items in an ice chest for up to 48 hours.
    4. Ask someone a favor of storing the items.

Defrosting of the Refrigerator and Freezer

  1. Turn off all controls.
  2. If you have an icemaker, turn off the water supply to it.
  3. Unplug the refrigerator.
  4. Completely empty out the refrigerator.
  5. Empty out the refrigerator's drip pan.
  6. Leave the refrigerator's doors open.
  7. If possible, place buckets or pans underneath the open doors to catch possible melting-ice drips.
  8. Monitor for drips for a day or two. Could be messy.

Tasks to do During Defrost Wait-Time

  1. Remove shelves, crispers, and other removables and wash them. (I washed mine in the bathtub using soapy dishwater.)
  2. Wipe the refrigerator interior surfaces with a solution of 2 tablespoons baking soda and 1 quart water. If your own manual specifies otherwise, follow that manual's instructions. Rinse with clean-water rinsed/wrung cloth. This stage might take several passes to wipe down all the surfaces.

DIY Door-open Alert Unit

The fridge door-open alert unit is useful to remind people to close the refrigerator door. After several seconds of the refrigerator door being open and the photocell being exposed to light, beeper emits a continuous whine. When the door closes, the sound decreases until the capacitor has been fully discharged. The device also serves as a good reminder to reduce time putting away cold groceries and also minimize dawdling in front of an open fridge.

The information and schematic for the Refrigerator Door Alarm is at http://www.techlib.com/electronics/kitchen.html. Note that the author suggests a 10uF capacitor across the battery, but doesn't show it on the schematic. (We omitted that capacitor also.) As this project is intended for a DIYer who does not require hand-holding and can fill in blanks, I have not included step-by-step information to create it.

If you are a hardware DIYer, you can obtain the parts fairly easily and breadboard and test the guts one day. Another day, you can wire and solder the discrete parts onto a project board, power the unit up, and have it operational. If you want to fancy it up, you can put the project into a metal project box, then set it in a small plastic tub to keep it off refrigerator shelves.

The parts came from hobby part drawers, Radio Shack (photocell from 5-pack 276-1657, buzzer 273-0059/273-059, 1/2 board 276-148), and Fry's Electronics (2 NTE123AP equivalents to 2N4401 transistor substitutes for the NPN Darlington transistor—seemingly not a commonly stocked part, zener diode NTE5009A). Overall packaging notes are as follows:

  • Already having a Bud Industries CU3000A aluminum project box on hand that measures 2.75" x 2.12" x 1.62"
  • Placing standoff-function hardware at the box's base to allow horizontal placement of a 9-volt battery (power source) beneath the assembled board—standoffs or spacers also suitable (Used 6-32 machine screws, nuts.)
  • Placing the buzzer outside the box for sound carrying (Used 2-56 machine screws, nuts.)
  • Drilling a hole on the box's side opposite the buzzer for light to reach the photocell

Note: In our case, we used a project box. When doing the final assembly, screwing the lid on required time that exceeded the time allowed before the alarm went off—an annoyance until the unit went inside the fridge and the noise fully abated.

Visit a lighter side of a refrigerator alert unit, which does not include a time delay before sounding off.

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