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Shut that fridge! (A quick and dirty fridge door alarm project) [Permalink]

Flats with shared kitchens. Urgh!

Flats with shared kitchens with one small fridge that is difficult to shut. URGH!

For those who don't know, I recently moved in to a flat in Cambridge for an internship during the summer. This morning when I went to get my flora out of the [very small] communal fridge, I found the fridge was slightly open and everything inside was warm. (Sigh) I had noticed that the fridge is awkward to shut, requiring more force than first anticipated. It isn't difficult to shut it but it is possible to not do it right in a hurry.

But anyway, this is the same story that you'll get from anyone who has built a fridge alarm.

So, this morning I went to maplin to get some stuff... (As always, Click image to make bigger)

Parts ready to build

What you see in the picture above is what I bought this morning when this happened. Yes, that was the cheapest way to buy 8 AA batteries, buy three times as much as you need.

These are only the pieces that the first maplin had in stock (St. Andrew's street). I had to cycle out to the 'beehive centre' to get some double sided sticky foam and a buzzer from a bigger maplin store.

It's a fairly simple build, there is an interval timer kit that uses a 555 to drive a relay. It's a little bit rubbish and I found that it doesn't have the range of times specified. It was, however, a thing that will do the job almost ready made. I connected the buzzer to the output of this timer circuit and routed the battery connections trough the microswitch. Now if the switch is not being pressed then the buzzer sounds for a short time at about once per two seconds ish. It was a very loud buzzer and so I put tape over the holes and mounted it in the box with generous amounts of double sided sticky foam to dampen the sound.

That's it really, here is the project mostly in its case... (you can see the buzzer, it has two white tabs with screw holes)

In the box

There is tape over the switch in that picture. I had to keep it quiet before it went on the fridge.

Full assembled

 This last photo shows the extra box I got that was stuck to the door of the fridge so that there was something there to press the button when the fridge was shut.

Got this all done before lunch time having started at about 9:00 AM.

So far it has worked fine apart from one slight nock of the button presser that meant it no longer reached the switch. A quick fix though. Let's hope the other users of the fridge appreciate the time and effort (and £29.11) I have put into making their food less likely to be ruined.

So here is a video...

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