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<p>[QUOTE=&quot;calcol, post: 4020043, member: 77639&quot;]OK.&nbsp; Here you go.&nbsp; A time-delay alarm for a safe deposit box.</p><p><br /></p><p>There are two circuit and one parts diagrams below. Circuit 1 is a little simpler and a little cheaper.&nbsp; The difference is that the alarm in Circuit 1 can be turned off either with the key switch or by pressing the lever of the lever switch (aka leaf switch) back to its down position, whereas the alarm in Circuit 2 can be turned off only with the key switch.&nbsp;&nbsp; With Circuit 1, a quick thinking thief might press the lever switch to shut-off the alarm.&nbsp; That won&#039;t work with Circuit 2.&nbsp; Chances are that when the alarm goes off, the reaction of a non-bank-employee thief will be to exit the bank ASAP.&nbsp; If the thief is a bank employee, their reaction will be a little harder to predict.&nbsp; A low level employee might run.&nbsp; A high level employee might try to bluff, saying they were doing some kind of test.</p><p><br /></p><p>There is a choice of low DC voltages that might be used for power.&nbsp; Delay relays (or modules) and buzzers can be found for 3, 5, 6, 9, 12 and 24 VDC.&nbsp; However, 12 VDC delay relays and buzzers are the most commonly available.&nbsp; You will want an on-delay (not off-delay) type.&nbsp; 12 V alkaline or lithium batteries are available or a 9 V and two 1.5 V batteries can be used in series.&nbsp; Leakage is rarely a problem with 9 V batteries; not so with 1.5 V alkalines. I recommend putting a baggie over the 1.5 volt batteries, and have had best luck with Energizer brand.</p><p><br /></p><p>The least expensive place to buy time delay relays for a project like this is eBay.&nbsp; Search would be something like &quot;time delay relay 12V&quot;.&nbsp;&nbsp; Be sure it&#039;s 12VDC, not AC, that it is delay-on, not delay-off.&nbsp; Some relays can go either way though.&nbsp; Most of the time delay relays in this search will be SPDT, which is OK for Circuit 1.&nbsp; For circuit 2, the search should be &quot;time delay relay DPDT 12V&quot;.&nbsp; You&#039;ll want a delay time in the 5-10 second range.&nbsp; You can also buy time delay relays from suppliers like Digikey, Mouser, Allied, and Newark, but will pay more.&nbsp; 12 VDC buzzers are widely available; be sure to get a loud one.&nbsp; And be sure to make vent holes in the project box for the sound to get out.</p><p><br /></p><p>The most elegant way to mount the leaf switch is inside the project box with a slot on top for the leaf, but mounting it on the side of the project box will work too.</p><p><br /></p><p>The alarm device should be duct-taped to the inside wall of the SDB high enough that the lid of the SDB will press the lever switch down far enough for it to be electrically open.&nbsp; This will prevent it from flopping over when the box is handled and setting off a false alarm.&nbsp; It will also prevent a thief from taking it out of the SDB and stomping it.&nbsp; Don&#039;t tape over the vent holes in the project box.&nbsp; Do not depend on the duct tape to hold the device off the bottom of SDB though.&nbsp; Put an appropriately sized wood block under the project box, and tape the wood block to the SDB wall too.</p><p><br /></p><p>I recommend putting a key for the key switch in an unmarked envelope in the SDB near the device.&nbsp; That should lessen the chance of an embarrassing false alarm if you open the box but don&#039;t have a key handy.</p><p><br /></p><p>Cal</p><p>&nbsp;[ATTACH=full]1057060[/ATTACH]</p><p>[ATTACH=full]1057061[/ATTACH]</p><p>[ATTACH=full]1057059[/ATTACH][/QUOTE]</p><p><br /></p>

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