; Fig. A: The alarm siren, straight out of the box.
; Fig. B: Secure the metal mounting bracket in a vise
and apply a hacksaw, using tape to guide your cut.
Don’t let the blade penetrate deeper than this.
; Fig. C: Snip the audio output wires.
; Fig. D: Unscrew the mounting bracket and carefully cut
away sealant around the power input wires. It doesn’t matter
if the wires are damaged. You can replace them later.
; Fig. E: Remove the screw to release the circuit board.
Opening It Up
The siren I chose is made by PUI Audio Inc.
You can find the data sheet at puiaudio.com,
and you can buy it from mouser.com or other
suppliers for $20 to $25. That’s cheaper than
a dog repeller, and the mods shouldn’t add
significantly to the price.
The PUI siren comes in a sealed plastic
case (Figure A). To get inside it, I selected a
fine-toothed hacksaw. The big question was
where to cut. In this situation I always ask
myself: if I designed this thing, where would
I put the components? In this siren I would
probably attach a little circuit board either
directly beneath the transducer or in the
bottom of the case. With this in mind, I started
cutting midway between these extremes.
I used bright green masking tape to guide my
cut, and barely allowed the blade to penetrate
Photography by Charles Platt
I found the electronics in the bottom of the
case, with red and yellow audio output wires
leading to the transducer. I clipped these
wires (Figure C), then unscrewed the metal
mounting bracket from the bottom of the
case and used a utility knife (Figure D) to cut
away sealant where the power cord entered.
Be very careful if you use a knife like this.
Always cut away from you!
After removing just one internal screw
(Figure E), I could pull out the circuit board.
Would it still work? I reconnected it with
patch cords and tested it with a 9V battery
(Figure F, following page). Everything was
still good. Now what?
143 Follow us @make