Home Alarm Design


Thread Starter

Israel Cabrera G.

Hi all,

i'm designing a home alarm and i want to know
wich is the best solution to make my alarm sound when I push a button or when somebody cuts the siren wire.
I'm using a 8051 uC.

please give some ideas on how to wire the siren,
and what are the best motion sensors to use with
it and how to wire it.
THANK's a lot!


Ramer-1, Carl


If you really insist on inventing the wheel, go for it, but for very little money you can buy a home security panel that has all of the normal security features, works with keypads, sirens, autodialers and all the rest of the devices required to form a system. The button you mention is called a panic switch and several vendors make burglar panels which accept wireless
panic switch signals. Almost every vendor's keypad has a panic and duress feature built in.

If somebody can get to your siren wire to cut it, the siren isn't going to work and the system failed already since it wasn't protecting its own components. A standard design element is self protection and self supervision of the system. The siren and its wiring should be within the protected perimeter.

The best motion sensors are the ones that suit your application, but you didn't describe the situation so it's hard to provide any help. There are high security sensors for areas where nothing is expected to be moving, sensors with pet alleys for people with cats or dogs that move around at night and some with dual technology and "smart" circuitry to reduce false alarms. Lots of choices and prices.

Carl Ramer, Engineer
Controls & Protective Systems Design
Space Gateway Support, Inc.
Kennedy Space Center, Florida
(V) 321-867-1812
(F) 321-867-1495
The place where u put your sensor is the main point that you should put in mind while you choose your sensor

1)i suggest that you use 89c52 up its easier and bigger memory 8kb flash
2)siren is made by 555 ic if you don't have full details contact me
3) you should impement a full monostable circuit for the alarm so its on
when someone goes in never off till u shut it down
4) a 555 based alarm is much more easier and also cheaper i have also full details contact me for more info
best regards
aladdin (aladdin122 @islamway.net)
> 3) you should impement a full monostable circuit for the alarm so its on
> when someone goes in never off till u shut it down

Note that having an alarm like that may be illegal in many places. Check the local laws and regulations, there may be a requirement for an alarm to shut off after 5 minutes, or some other limitation.

As a practical matter, you'll probably find your alarm smashed if it goes on and on and won't shut up.

Jiri Baum <[email protected]> http://www.csse.monash.edu.au/~jirib
MAT LinuxPLC project --- http://mat.sf.net --- Machine Automation Tools

sibasish mahapatro

I sibasish mahapatro as an employer of airpac export which is pharmacitical company. I worked here as a design engineer, I am dip.in electrical, & degree in electronics.
In my point of view, As you are going to design a home alarm so you must use the following step i.e.
1.use 89c51, because it has in built 4k eprom
2.you should design a good detector circuit with having delay circuit & counter.
3. detector circuit detect the object that is at the door,the o/p comes out in terms of vtg then you should compare it with some fix reference reference value,if the o/p is matched , then as per our software the o/p connected relay was no, and the o/p from relay connected to a buzzer,
*with detector you should also take a pushbutton switch to pass the press signal.
with best regards
sibasish mahapatro