DIYbanter - View Single Post - Derive low voltages signal/output from PIR floodlight?

formulated the question :
I would like to derive an audio alert from a PIR floodlight. To be more
specific: let's say I have the floodlight above a back window and
driven from a three-pin plug from inside. I would be happy to bring
additional cabling from the PIR.

Or maybe forget that floodlight (I have another outside fed from the
garage) and use an external low voltage PIR to feed an audio alert
and/or switch on a light (even low voltage). I doesn't have to be DIY;
off the shelf solutions welcome!

Just thinking ... I suppose there is nothing to stop me feeding 240V
back from the switched supply to the floodlight.

Rationale: I'm interested in being alerted about potential burglaries
/before/ they enter; a few nights ago I heard was awoken by burglars
attempting to force a window. I assume also, that an audion alert just
loud enough to be heard outside might be a deterrent.

I'm sort of reluctant to fit a proper alarm; many reasons, but the main
one is that they tend to elart you only after the burgulars have gained
entry.

TIA,

Jon C.

I have 3x hard wired 500w PIR's and was faced with the same problem. My
solution was to find a small tranformer with room to wind a few turns
of one of the mains supplies around the core (around 5 turns). I then
used the original windings of the transformer to supply a bridge
rectifier with a small capacitor across the DC output, to which I then
connected a 12v piezo sounder via a switch so it could be disabled.
This will need to be the type with a built in oscillator.

The mains cable I chose fed all three lights, so if one PIR is
triggered the piezo will sound, more lights trigered equals more noise.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.org