This is a follow on from Hippo's "Key with lock status indicator" idea.

Ever gone to bed and then worried if you've locked the garage or the shed ? Did you lock the back door after you let your cat out to prowl around, crapping in other people's gardens, killing <SQUELCH ... end of anti-cat rant>.

What you need is a lock status inidcator system. Very similar to an existing wireless burglar alarm, next to each lock is a small transciever unit. A sensor (reed relay or microswitch) is fitted inside the striker plate of the lock. Whenever the bolt moves in or out of the striker plate, the transmitter sends an "open" or "closed" signal to the central monitoring unit. The CMU has individual LEDs for each lock, and a big coloured panel which shows green for "all secure" and red for "at least one door not locked". The CMU would for preference be installed next to the normal final exit door from the building to give the user status indication as they left. Intruder alarms will generally detect if a door is not closed, but won't detect if a door is not locked.

A remote reperater could be installed in a bedroom etc. for peace of mind during the hours of darkness.

The idea of a wireless system is that it would be very quick and easy to retrofit. A cabled system would no doubt be cheaper to make, but more expensive and disruptive to install, especially if monitoring outbuildings etc.

This is NOT an intruder alarm per se, although the functionality could be easily built into existing alarm designs.
-- 8th of 7, Aug 22 2002

Key with lock staus indicator http://www.halfbake...0status_20indicator
Hippo's complementary idea [8th of 7, Aug 22 2002, last modified Oct 05 2004]

electric latch http://www.videx.com
baked [pashute, Jun 02 2010]

What sort of range do people see this device having? Because that has a big effect on the sort of wireless networking involved, and therefore the cost.

- global = mobile telephone cells, or worse GPRS
- 50 to 100 metres is Airport / 802.11b
- a few metres is Bluetooth
- only as not-quite-wired together could be infra-red

A single wireless device may not sound expensive, but you're talking about quite a few of them: one in each lock, one in your home repository (computer), and one in output (keyring, bedroom repeater).
-- sadie, Aug 23 2002


This system is short range - 100 metres tops - but will have to have some ability to propagate through building structures. I envisaged using the existing deregulated band allocated for home security systems. These systems sell at about USD $150 depending on complexity but that would generally include the control panel and about 4 detectors.
-- 8th of 7, Aug 23 2002


did I read that right? //you let your cat out to prowl around// 8th has a cat? will someone send the RSPCA round to check it out.
-- po, Aug 23 2002


po: note use of second person, not first person ...
-- 8th of 7, Aug 24 2002


take that as a no then. (sigh of relief).
-- po, Aug 24 2002


Or take the ultra-secure approach with self-closing, self-locking doors. No user action required. Whenever you go out, you always have peace of mind knowing that all of your valuable possessions (like your keys, for instance) are locked safely inside your home.
-- BigBrother, Aug 24 2002


There is some serious research going on in this area - check out www.electric-latch.com
-- rabbit2, Apr 06 2003



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