ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
Linear Power Supply Quits Under Load
by JoeTestingEngr. 10/18/18 08:47 PM
220/230/240V 60Hz Systems
by dsk. 10/17/18 01:25 PM
PLC/HMI Enclosure C2, D1
by ghost307. 10/16/18 03:31 PM
Tingle off the water spigot
by dsk. 10/15/18 02:36 PM
New in the Gallery:
What is this for?
Plug terminals
Who's Online Now
1 registered members (JoeTestingEngr), 18 guests, and 35 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Theft deterrent alarm #218839
11/04/17 06:15 PM
11/04/17 06:15 PM
M
Merlin  Offline OP
Member
Joined: Jan 2004
Posts: 171
NW Indiana
I have a request to build a theft deterrent alarm for a customer to protect a product display. I have seen similar situations at implement dealers. This systems needs to comprise of a cord that is weaved through the display. Once connected, an alarm will be activated. If this cord gets unplugged or cut, it will sound an alarm and light up the display.

I am looking for some ideas on how to make this work flawlessly.

Work Gear for Electricians and the Trades
Re: Theft deterrent alarm [Re: Merlin] #218840
11/05/17 02:41 AM
11/05/17 02:41 AM
G
gfretwell  Online Content

Member
Joined: Jul 2004
Posts: 9,298
Estero,Fl,usa
The easiest way I have seen is to use a SCR with a pull up resistor from the +vcc to the gate and the alarm trigger wire is grounded. As long as that circuit is completed the gate is held low but if the wire is cut, switch opened or whatever else in the circuit opens the resistor pulls the gate high and triggers the alarm. You need to drop power, restore the circuit and power it back on to reset the alarm. Simply reconnecting the wire will not shut off the SCR.


Greg Fretwell
Re: Theft deterrent alarm [Re: Merlin] #218845
11/10/17 05:09 PM
11/10/17 05:09 PM
Potseal  Offline
Member
Joined: Feb 2013
Posts: 264
Saskatchewan


A malfunction at the junction
--------------------------------------
Dwayne
Re: Theft deterrent alarm [Re: Merlin] #218849
11/12/17 04:08 AM
11/12/17 04:08 AM
G
geoff in UK  Offline
Member
Joined: Dec 2002
Posts: 193
UK
This is a commercial one I've seen used here. I imagine similar are available on your side of the water. Be hard to make something cheaper. https://www.insight-security.com/retail-display-alarms-and-loop-alarms

Re: Theft deterrent alarm [Re: Merlin] #218850
11/12/17 02:39 PM
11/12/17 02:39 PM
G
gfretwell  Online Content

Member
Joined: Jul 2004
Posts: 9,298
Estero,Fl,usa
The one I described could be made pretty cheap, with the relay or SSR being the most expensive part.
Any DC source, wall wart or battery would work and if your noise maker was also low voltage DC, you could eliminate the relay/SSR and put your alarm device there. This design turned on 120v flood lights and a claxon via the relay.

[Linked Image]


Greg Fretwell

Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
Niko
Niko
Campbell, CA
Posts: 356
Joined: August 2006
Show All Member Profiles 
Top Posters(30 Days)
sparky 11
Popular Topics(Views)
250,521 Are you busy
188,080 Re: Forum
177,717 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.019s Queries: 15 (0.004s) Memory: 0.9695 MB (Peak: 1.1120 MB) Zlib enabled. Server Time: 2018-10-21 04:53:49 UTC