Mreadinger
New Member
Ok so i saw this video on Youtube (YouTube - Protect Your Home with Lasers!) on how to build a laser trip-wire alarm system. A simple project where if you cross the path of the laser an alarm will sound.
The parts it requires are:
1- 5kΩ Variable Resistor
1- 9V Battery Connector and battery
1- 2N3904 Transistor
1- 12V Siren
1- Photocell
Here is the schematic that is given in the video (sorry these are hand drawn and scanned onto my computer)
<a href="http://s126.photobucket.com/albums/p117/greenchix/?action=view¤t=origional.jpg" target="_blank"><img src="http://i126.photobucket.com/albums/p117/greenchix/origional.jpg" border="0" alt="Schematic"></a>
Here is the schematic i made from this (i think it is the same as the top)
<a href="http://s126.photobucket.com/albums/p117/greenchix/?action=view¤t=untitled.jpg" target="_blank"><img src="http://i126.photobucket.com/albums/p117/greenchix/untitled.jpg" border="0" alt="other"></a>
When i breadboard this though the siren ends up sounding no matter what. I have a few questions about this circuit
1. How exactly does this circuit work?
2. If the Resistance is lower on the photocell with the laser on , why is it that the siren sounds when the laser is off
3. Any ideas to fixing my problem
I will be very grateful to any ideas to help me fix my problem. Thanks!
The parts it requires are:
1- 5kΩ Variable Resistor
1- 9V Battery Connector and battery
1- 2N3904 Transistor
1- 12V Siren
1- Photocell
Here is the schematic that is given in the video (sorry these are hand drawn and scanned onto my computer)
<a href="http://s126.photobucket.com/albums/p117/greenchix/?action=view¤t=origional.jpg" target="_blank"><img src="http://i126.photobucket.com/albums/p117/greenchix/origional.jpg" border="0" alt="Schematic"></a>
Here is the schematic i made from this (i think it is the same as the top)
<a href="http://s126.photobucket.com/albums/p117/greenchix/?action=view¤t=untitled.jpg" target="_blank"><img src="http://i126.photobucket.com/albums/p117/greenchix/untitled.jpg" border="0" alt="other"></a>
When i breadboard this though the siren ends up sounding no matter what. I have a few questions about this circuit
1. How exactly does this circuit work?
2. If the Resistance is lower on the photocell with the laser on , why is it that the siren sounds when the laser is off
3. Any ideas to fixing my problem
I will be very grateful to any ideas to help me fix my problem. Thanks!