simple loop alarm for exhibits

I always stamp my postcode into my boilers as part of the boiler number.

I better not move house!

Sorry J D but I don’t know where you’ve been hiding but this sort of pilfering has been going on for years hence the fact that most mME clubs who exhibit at exhibitions have their own loop alarms as even the most eagle eyed stewards cannot watch everything all the time. Pretty sure I have seen a club stand with cctv at one of the big shows. I had a friend exhibiting homemade aero engines at forncett and these were wired with Bowden cable but odd cranks rods pistons and rings laid on the stand, these are the sort of things that go.

Strewth. Why are people such sh*ts these days? There is organised pilfering too, where people just go behind the tills at shops and take fags and booze - threatening staff if they try to prevent them.

Stop the World - I want to get off !

It would seem difficult to run a wire through every little component. I guess that exhibitors will have to build perspex boxes over their displays, and serve customers like they used to in shops; from display cabinets only open to the inside of the stand.

Fortunately, our club has only experienced one instance of theft.

My wife fund raises for a charity and has had lots of stuff stolen, that has to be really low!

Eventually, you get a sense of who to watch, groups of youngsters, in particular.

The worrying thing is that sometimes workshop tooling, as well as models, might be stolen, and then abandoned because the thief has no idea what it is, or is for. But the owner is still deprived of the item and the material, time and effort put into making it.

As Stewards, you have to keeps your wits and eyes about you. As you say. be aware of distractions!

Howard

Howard

As you are back on this thread … I would be most grateful if you could answer my earlier question

01/10/2023 18:34:11

… it’s really niggling me … have I missed a very clever trick ?

MichaelG.

Michael,

I don't reaslly understand details of the alarm, (The club bought it), so tend be a user rather than knowing much about it.

If the circuit is broken for any reason, the alarm sounds is about the extent of my knowledge, so assumed that it relied on a switched 3.5mm jack socket.

Howard

It could be a voltage reference or a logic pattern feeding the wire loop, and a check that the received voltage or signal is the same. This could all operate at minimal current both in the wire and in the circuitry, so allowing a long battery life.

I'm a bit late to the party, but FWIW I'd imagine something like this:

The loop of wire carries a small current of about 2 mA until it is broken, whereupon the RON sounds. At the very least it advertises to the stewards they they need to look over their stall carefully. You can't sit there all day long concentrating on everything, you'd go barmy. You do need to test it periodically say twice a day as it's not failsafe.

If anyone wants the bits to make something like this PM me, I've got only one RON so first come first served. Alternatively if it helps I can point to suitable components on ebay if that's OK with the mod's.

Note there are two basic types of piezo squawkers, one makes a continuous noise, the edgier the better, the other needs an oscillating signal to drive it as it is intended as a low cost speaker. Only the first type is compatible with this simple cct.

I've seen something along these lines with the loop made of sections of coax TV connectors. That way you can have as many sections as you wish. The lengths of cable sold for ear phone extensions with 3.5 mm jack connectors would also suffice. You need something that shouts to the scum bags that there ain't no way you're going to =get away with anything while not becoming the focus of the exhibit.

That's pretty much what mine is, but I think I remember using a thyristor instead of a transistor so once triggered it keeps on blaring away until you disconnect the battery. having a little local difficulty retrieving it from the ex club member who has it at his house, will send in the heavy mob soon!

I put a few banana plug/sockets in the loop to keep lengths manageable, you need a surprisingly long bit to go through a lot of models

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Thanks for your candid response, Howard … I was probably reading too much into your statement that the wire carried no current.

MichaelG.

Edited By Michael Gilligan on 03/10/2023 17:10:24

Hopefully the battery would only be required to deliver current when the circuit is broken and the alarm activated..

I didn't phrase it very well.

Howard

Thanks again, Howard … I am happy to accept the spirit of what you wrote

I had no intention of nit-picking … just part of my ongoing quest for understanding.

MichaelG.

Extraordinary what risks a brainless thief will take. Many years ago, when ArcEuro and Maidstone Engineering had stands, along with other tool stands, there was a crowd gathered around another toolstand and I was at the back of the group. Someone on my left asked the stand holder a question, distracting him and someone on my right grabbed a handful of wooden file handles and disappeared. Probably only about 50p each then. I have seen small cheap items lifted a large chemist's and the culprit marched out fast. Also seen man and woman pushing small child in buggy around Debenhams, picking very expensive, at that time, £50 shirts, casually fold them up and place them on the shelf under the buggy. I had them stopped by Security. All very well having Alarm cables but only suitable for models on club stands. Potential trade stand customers want to pick up and examine items before purchasing. I think the kind of cctv screens used by supermarkets at their self checkouts would probably drive prospects away. Cost would likely be prohibitive for that purpose. I think you will find that the cheapest items are nearest the front on traders stands. I often buy eggs from a market stall in Brighton run by Steve Ovett's family. After he won an Olympic gold medal, it was put on display right at the back of the stand! Perhaps large Perspex type screens could be used for model and small tool displays.

Edited By DMB on 03/10/2023 22:17:19