You can
pickup a very loud 100db+ siren
from many electronic suppliers as well as Kronos Robotics. The
problem is you cant drive them directly from you microcontroller. In
this application note I will show you how. With just a 1k
resistor and transistor you can drive them from you microcontroller.
By changing how long you supply power you can even change the type and
volume of sound that the siren emits.
Hookup is simple. Just a single
transistor and resistor are needed for creating a direct drive Kronos
Siren. This application can also be applied to just about any siren
as long as it does not pull more than about 600ma.
What I'm going to show you is step by step
instruction on how to modify the inside of the siren shown.
Remove the
2 screws shown
Pull the
little circuit board out of the main case. We are going to remove
the this black wire from the pad shown.
Here you
can see the wire removed
Take the
TPN2222 transistor and solder a 1k resistor to the B lead as shown.
Then
solder a 8" piece of wire to the other end of the transistor as shown.
Place some
1/16" heat shrink over the resisor as shown. Trim the other
two leads as shown. Then tin the leads with solder.
Solder
the C lead to the pad as shown. Note the flat portion of the
transistor is facing up.
Solder
the removed black lead to the E lead on the transistor as shown.
Place some 1/16" heat shrink over the connection.
Replace
the circuit board and pack the transistor in place so the leads exit the
small hole shown. Make sure none of the connections have a
chance of touching. Replace the back and screw in place.
Connect the black lead to Vss.
Connect the red lead to Vcc. Connect the green lead to the IO
port of your microcontroller. When the port is high the alarm
will sound.
I welcome other
observations or remarks. Just contact me at
msimpson@kronosrobotics.com
Parts
list
Siren
NPN Transistor
Heat Shrink
7.5V AC Adapter
9 Pin Cable
Breadboard and
Wire Kit
Breadboard
Regulator
