DIYbanter - View Single Post - Intruder alarms

Andrew Gabriel

In article ,
(A.Lee) writes:
I've been asked to fit an alarm for a customer.
They currently have a wired one that is 20 years old, so needs replacing
as it is falling apart, especially the door sensors.

Fitting a wireless one would be far easier for me, but are they reliable
enough?

What are you protecting it against?
A clueless stoned druggie looking for something to sell quick,
or a professional thief targeting something specific?

Wired systems can be more secure against the latter and they tend
to be better, with a wider range of options, but there's an overlap
and the best wireless systems will be better than a low end wired
system.

Wireless systems should be regarded as non-extendible and non-
repairable, as the chances of finding compatible parts a few years
on will be very low. Conversely, additional and replacement wired
sensors will always be available, and you will likely be able to
add new sensors at a later date which haven't been invented yet.

If not/so, then could someone recommend an alarm for a bungalow, 3
doors, plus maybe 2 movement sensors in the conservatory and garage?

Both conservatory and garage can be liable to false triggering from
PIR sensors, due to significant sources of heat causing movement of
hot air - conservatory from the sun, and garage from a parked car
with hot exhaust/engine. In these cases, a dual tech sensor (PIR
and microwave) may be necessary, although in a conservatory, careful
adjustment of microwave power will be needed to avoid sensitivity
from outside the glass.

You probably want a PIR somewhere in the body of the house, such as
the main room or hallway, as door sensors are only perimeter detection
and don't cover the volume of the house accessed via other routes such
as broken window access.

I suggest that, particularly if you are not familiar with designing
sensor layouts, you initially leave the external sounder disconnected.
Wait for at least a month or more of no false alarms before connecting
it up, and all false alarms in this period are explained and the cause
fixed. Otherwise, the good will of the neighbours will be lost before
the alarm is working, and they'll take no notice of a real alarm later.

--
Andrew Gabriel
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