Wire Loop Alarm

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Author	Views	Views Today	Rank	Comments
Alex Meaden	208,180	5		27

This circuit is a simple wire loop alarm that can be used in doorways, hallways, or any other place the tripwire will be broken by intruders. The circuit has a built in siren, but it can be replaced by a relay to drive an external siren, commercial alarm, etc.

Schematic

Parts

Part	Total Qty.	Description	Substitutions
R1	1	100K 1/2W 1% Resistor
R2, R4	2	10K 1/2W 1% Resistor
R3	1	1 Meg 1/2W 1% Resistor
C1, C3	2	0.1uF Ceramic Disc Capacitor
C2	1	0.01uF Ceramic Disc Capacitor
IC1	1	4001UBE Quad 2-i/p NOR Gate
Q1	1	MPSA14 Low Power NPN Transistor
SIREN	1	Micro piezo siren 12V DC 150mA, 110dB @ 1M
LOOP	1	See "Notes"
MISC	1	Board, Wire, Socket For IC1

Notes

Email Alex Meaden with questions, comments, etc.

The loop can be any type of hookup wire, with a maximum resistance of about 90K. Using very thin wire (40AWG, for example) will make a very sensitive trip wire, but will shorten the distance it can be strung due to the high resistance.

The siren can be replaced with a relay to drive external loads.

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Comments

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anonymous Wire Loop Alarm Sunday, March 22, 2009 10:43:54 PM

hi i need your help, i picked the wire loop alarm as a project for school and i was just wondering if you can help my by answering some questions that kept me awake for some time and i need technical answers if its not too much trouble. why does the siren stay on when you reconnect the loop and second what are the jobs of the 7th and 14th pin and why are they connected in that way i would really appreciate you answer on this .

anonymous Wire Loop Alarm Friday, November 07, 2008 1:21:39 AM

hi, just wanna ask how long wire this circuit will work? if transistor i change, with kind of what transistor?..thx

anonymous Wire Loop Alarm Tuesday, October 07, 2008 4:59:01 AM

can we replace the siren to a buzzer type and what if we use a solid wire could it be work in this kind of circuit.

anonymous Wire Loop Alarm Friday, August 15, 2008 10:50:53 AM

can we use IC 4002 instead???...plz help!!

Eric Wire Loop Alarm Saturday, August 02, 2008 2:10:16 AM

Will this work with a 200m or more length of wire loop??

Dan Wire Loop Alarm Thursday, February 28, 2008 3:48:23 AM

Hey. Thanks for this circuit. I found other loop alarms hard to get working. Can you please send me more information about the alarm. Many Thanks ! Dan

ritesh Wire Loop Alarm Monday, January 14, 2008 10:06:26 AM

which loop should we use is it simple wire loop or which thing is used

kavinilavu Wire Loop Alarm Wednesday, January 02, 2008 7:51:30 AM

what is the use of the circuit & explain how it works

dD Wire Loop Alarm Sunday, November 25, 2007 11:29:51 AM

can u give me the detail?a.s.a.p i think i want to add other circuit.. i want to add autolock circuit.. oh i want to send the signal to my room or other..

anonymous Wire Loop Alarm Wednesday, November 21, 2007 9:19:39 AM

hi there!just wanna ask if you do have the data sheet of each part/material of your wire loop alarm?if so, can you please send it to my e-mail coz i really need those data for our design...hope you can help me...thank you and God bless...

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anonymous	Wire Loop Alarm	Sunday, March 22, 2009 10:43:54 PM
hi i need your help, i picked the wire loop alarm as a project for school and i was just wondering if you can help my by answering some questions that kept me awake for some time and i need technical answers if its not too much trouble. why does the siren stay on when you reconnect the loop and second what are the jobs of the 7th and 14th pin and why are they connected in that way i would really appreciate you answer on this .
anonymous	Wire Loop Alarm	Friday, November 07, 2008 1:21:39 AM
hi, just wanna ask how long wire this circuit will work? if transistor i change, with kind of what transistor?..thx
anonymous	Wire Loop Alarm	Tuesday, October 07, 2008 4:59:01 AM
can we replace the siren to a buzzer type and what if we use a solid wire could it be work in this kind of circuit.
anonymous	Wire Loop Alarm	Friday, August 15, 2008 10:50:53 AM
can we use IC 4002 instead???...plz help!!
Eric	Wire Loop Alarm	Saturday, August 02, 2008 2:10:16 AM
Will this work with a 200m or more length of wire loop??
Dan	Wire Loop Alarm	Thursday, February 28, 2008 3:48:23 AM
Hey. Thanks for this circuit. I found other loop alarms hard to get working. Can you please send me more information about the alarm. Many Thanks ! Dan
ritesh	Wire Loop Alarm	Monday, January 14, 2008 10:06:26 AM
which loop should we use is it simple wire loop or which thing is used
kavinilavu	Wire Loop Alarm	Wednesday, January 02, 2008 7:51:30 AM
what is the use of the circuit & explain how it works
dD	Wire Loop Alarm	Sunday, November 25, 2007 11:29:51 AM
can u give me the detail?a.s.a.p i think i want to add other circuit.. i want to add autolock circuit.. oh i want to send the signal to my room or other..
anonymous	Wire Loop Alarm	Wednesday, November 21, 2007 9:19:39 AM
hi there!just wanna ask if you do have the data sheet of each part/material of your wire loop alarm?if so, can you please send it to my e-mail coz i really need those data for our design...hope you can help me...thank you and God bless...