How to Wire a Buzzer to a Motion Detector

Unplug the stand-alone motion detector's power cord from the wall outlet. If there is a battery compartment lid on the back of the detector, open the compartment lid and remove the battery backup inside. Close the lid.

Place the detector on a work surface with the back facing you. Remove the screws from the four corners on the back of the detector with a Phillips jeweler's screwdriver or a Torx screwdriver, depending on the make. Remove any screws from the bottom back edge as well.

Grip the sides of the detector and pull the outer case straight up or, if there are rails on the sides of the detector, toward you instead. Remove the outer case from the detector and place it aside.

Heat up the soldering iron for five minutes. Locate the built-in horn that is inside the detector; it is flare-shaped and unlike any other component so it is easy to find.

Touch the tip of the soldering iron to the "+" labeled contact at one end of the horn. Remove the tip after five seconds have passed. Pull the wire that was soldered to the "+" labeled contact off with a tweezers. Snip the wire with wire snippers to prevent it from being able to touch the contact. Dispose of the cut wire in the trash.

Repeat this procedure with the soldering iron and the "-" labeled contact on the horn.

Solder the exposed end of one of the two electric wires to the "+" labeled contact. Let the solder cool for a minute. Make a dot on the insulation at the other end of the wire with a grease pencil. Solder an exposed end of the other electric wire to the "-" labeled contact. Let the solder cool for two minutes before continuing.

Grip a section of the left side of the outer case with the jaws of the pliers. Twist the pliers to distend the section of the case the jaws are clamped to.

Place the outer case back on the detector; run the wires from inside the detector out of the distended edge on the case's side. Reattach the screws to the outer case.

Solder the exposed end of the wire that has a dot on it to the "+" labeled contact on the buzzer. Let the solder cool for a minute. Solder the exposed end of the other wire to the "-" labeled contact on the buzzer. Let the solder cool for a minute. Unplug the soldering iron.

Reinsert the battery into the battery compartment, if one is present. The stand-alone motion detector can now be plugged in and used as before, only now the buzzer will sound instead of the built-in horn.