Security window foil and connectors - can you still buy them?

[Martyn Pollard]

Some of you should remember this from the 80's. Strips of stick on foil for windows which were laid in a loop pattern. When the window was smashed the alarm was triggered. The adhesive connectors provided a screw terminal onto the foil strips.

I am making an open door alarm for two fridges and a freezer due to people accidentally leaving the doors ajar. The freezer goes bonkers and quickly creates a lot of frost which has to be cleared out. I need some type of contact which will be open when the door is even just a few mm open. A microswitch would seem logical but mounting them could be a problem and i dont want to use self tappers. So how about security foil? A small vertical strip along the door seal which when door is closed makes contact with adjacent strips on the door frame. The connectors are then wired to an alarm circuit.

I have looked at other off the shelf solutions including light triggers, but the fridge light turns off even if the door is a centimetre open and it wouldn't be any use for the freezer. The doors are weighted to close, but if the internal drawers aren't pushed all the way in, the door remains slightly open.

Martyn

[John Rumm]

I have a feeling most of these foil tapes were PVC backed, and hence may not do what you want.

How about a suitably positioned reed switch and a magnet - either the alarm type or the unpackaged device if you want small an unobtrusive. You can then tune the gap to activate the alarm at the required amount of openness.

[Colin Wilson]

See if you can get hold of a reed switch for an alarm (i.e. the sort you'd see on door alarms with a block on the door, one on the frame)

Many of them have a normally open and a normally closed contact position, and you could simply glue them on the outside of the fridge, and use a simple series circuit;

battery +ve -> reed switch -> sounder -> battery -ve

[Adam Aglionby]

Poundland have 2 cupboard lights for a quid that use a reed switch and some LEDs very hackable, if the supplied magnet is too far away NiB magnets have a better range.

Adam

[nightjar]

You also used to be able to buy something similar for making bespoke electric model car racing circuits.

Colin Bignell

[Bob Eager]

A sideways look...when this was a problem on the freezer, I used an internal/external digital thermometer, stuck on the outside of the freezer, with the 'outside' sensor stuck on the inside (the thin wire wasn't a problem in the door seal).

The one I used had a high temp alarm...

[Chip]

On Sat, 26 Jan 2008 00:50:50 GMT,it is alleged that Martyn Pollard spake thusly in uk.d-i-y:

[snip]

Other posts in the thread have probably solved the issue with better solutions anyway, but I haven't been able to locate window foil or terms since Maplin stopped selling them (along with anything else useful they used to sell).

You can however get copper tape, gardening suppliers sell it on ebay for deterring slugs. It's also useful for screening etc. of small enclosures and is very easily soldered to (being copper).

[geoff]

In message , Martyn Pollard writes

Give the fridge a slight tilt so that the door closes naturally

[Andrew Gabriel]

I can just picture a garden gate closer screwed to the edge of the door...

[George]

It was replaced with vibration sensors for the simple reason the foil sometimes did not tear especially on small windows.

But this is what you're after.

[Colin Wilson]

On a slightly different note;

We had a dog that used to like nicking toilet rolls - we ended up with one of the "sprung flap" holders, which we had to mount upside down to prevent it getting more than one sheet at a time !

[Andy Dingley]

Or more commonly, the foil was a couple of years old and no longer firmly attached to the glass. The glass broke, and the foil was left hanging intact..

[geoff]

In message , Andrew Gabriel writes

I was just picturing tweaking the legs so that the door closed naturally

[Andrew Gabriel]

Often used to see the foil clearly broken, often when something had rubbed against it or the end contact had come adrift. A sure sign that the burglar alarm was not working or maintained...