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.
|
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 |
|
1. Email Alex Meaden with questions,
comments, etc.
2. 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.
3. The siren can be replaced with a
relay to drive external loads.
