# What is the simplest way to prove the light turns off in the refrigerator when the door is closed?

Dr. Penny Pincher founded the popular personal finance blog Penny Pincher Journal in 2013 and has published two books about saving money.

## Problem: Observe the Unobservable

I posed the question "What is the simplest way to prove the light turns off in the refrigerator when the door is closed?" on Hubpages to see what ideas people could come up with to determine whether or not the light inside a refrigerator actually turns off when the door is closed. Here are the criteria I had in mind to determine the best solution:

• Must not damage the refrigerator
• Must provide direct evidence or proof that the light turns off when the door is closed
• Simple solutions preferred
• Inexpensive approaches preferred
• The simpler the better!

## Simplest Solution?

One solution was to simply press the button that the door presses when closed. If you press this button with the refrigerator door open, you can observe that pressing the button causes the light to turn off. This is simple, and does show that pressing the button causes the light to turn off.

But does the door firmly contact the button when closed? You could assume that it does. You could even measure the clearance and build a case that the door must press the button in far enough to trigger it when the door is closed. However this does not really provide direct proof. This solution gets points for simplicity, but does not provide proof that closing the door causes the light to turn off.

## Going High Tech

The best solutions suggested using a video camera to record the action inside the refrigerator before, during, and after the door closes. This would provide direct evidence that the light turns off when the door is closed. Since the video camera is self-contained, it will not interfere with the closure of the door.

I think 15 or 20 years ago, this would not have been a simple solution since video cameras (or cell phones with video cameras) were not readily available. But now most cell phones have a video camera built-in. You can buy cheap digital video cameras that use flash memory for less than \$30.

## Isn't There a Better Way?

It seems that something simpler than recording video would be possible to determine whether or not the light turns off. A video camera records thousands (or millions) of pixels per second of video data. A simple experiment would take several seconds- this means that a few megabytes of data would be recorded to determine whether or not the light does in fact turn off. That seems like a lot of data.

It seems like only a few bits of data should suffice- rather than the megabytes of data provided by a digital video recording, but I have not thought of a simpler sensor to use than the video camera.

One thought was to check the temperature of the lightbulb- you could leave the refrigerator door open and let the lightbulb heat up to reach a stable temperature. After closing the door for some amount of time, the lightbulb should cool off if the lightbulb does actually turn off while the door is closed. Non-contact Infrared thermometers are available for about \$20- these can be used to check for areas of your house that can benefit from additional insulation or caulking. But a \$20 thermometer and a test procedure that may take several minutes is not as simple as using a video camera to obtain direct observations.

## Proof that the Light in a Refrigerator Turns Off when the Door is Closed

Now it's time to apply the simplest method- digital video recording- to prove whether or not the light in a refrigerator turns off when the door is closed.

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It took about 30 seconds to record video evidence that the light in the refrigerator does turn off when the door is closed. The video below shows about 5 seconds of placing the camera in the refrigerator. Then the door closes and the light turns off, which is recorded for about 5 seconds. Next, the door is opened and the light turns on again.

## The Verdict: Does the Refrigerator Light Turn Off?

Yes, the light in a refrigerator does actually turn off when the door is closed.

Incandescent Light Bulb Ban

© 2013 Dr Penny Pincher

Dr Penny Pincher (author) from Iowa, USA on April 18, 2016:

Amandine- You idea is efficient, I like it!

Amandine on April 14, 2016:

Hey guys !

To avoid this large amount of data by recording, it suffices to have a camera with a self-timer and to ensure that it takes a picture (without flash) when the door is closed ! Thanks fot this article though, it was interesting to read.

Dr Penny Pincher (author) from Iowa, USA on March 25, 2013:

Great story! Think of all the energy- and money- you saved by checking that the light actually turns off.

Chandrakanth on March 24, 2013:

I was 8 years old when we had our first refrigerator (over two decades ago), and I remember the installation guy telling me how the light-off mechanism works when door is closed. The mechanism was "ingenious" to me then. I wanted to verify its working, and did it by simply peeking my fingers thought the door gasket and surprised to see the light seeping from inside. The mechanism wasn't working and the light was ON even with door closed (no LEDs those days and it was conventional 15W incandescent lamp wasting power). We complained and a service guy came. Problem was fixed by moving the lamp-unit a little forward so that the light switch was now within the reach of a protuberance attached to door. Same technique verified that the switch-off was now working.