Hi, this is Wayne again with a topic “DIY Hacks & How To’s: Laser Tripwire”.
In this project, i’m going to show you how to build a laser tripwire alarm to make it all you need is a simple laser pointer and a few dollars worth of electrical parts. The alarm circuit is built around a 555 timer ic. It uses a photoresistor to detect the light from the laser pointer. The photoresistor is wired in series with a second resistor that together form a voltage divider. The value of the second resistor should be about the same as the photoresistor when the laser is shining on it.
In this case, it was about 100 ohms when the light beam is interrupted. The resistance of the photoresistor increases and the voltage at pin 6 goes above the reference threshold. This causes the output at pin 3 to go low and activates the alarm to turn off the alarm and reset the system. The switch disconnects the speaker and sends the low signal to the trigger at pin 2. flipping. The switch back will reactivate the system.
First assemble. The circuit on a breadboard to test it if everything is working properly solder it all together in a printed circuit board. I mounted the photoresistor so that it sticks out about an inch from the board. That way you can adjust its position after mounting it. The batteries in the switch are mounted to the board with hot glue, then to keep all the loose wires under control.
I wrapped a rubber band around the board. Now it’s time to set up your trip wire, the simplest configuration is a single beam trip wire for this. The laser pointer is mounted to one side of a walkway, and the alarm circuit is mounted to the other first tape. The alarm in place to keep the laser pointer on i use tape to hold the button down. Then i use sticky tack to mount the laser pointer in place carefully, adjust the laser pointer so that the beam is centered on the photoresistor.
Lastly, flip the switch to activate the alarm now whenever someone walks through the beam, the alarm will go off. A single tripwire beam works fine, but with the addition of a few mirrors, you can cover a whole room and a grid of criss-crossing lasers to set up a multi-beam tripwire start by mounting the laser pointer. Then, at the point where the beam hits the opposite wall mount a mirror at a slight angle continue adding as many mirrors as you want. The last mirror should direct the light to the alarm circuit, because the system uses one continuous laser. If any of the beams are interrupted, it will cause the alarm to go off. If you find that the laser pointer’s battery life is too short, you can remove the three button cell batteries and instead power it with the three double a batteries on the alarm circuit, because they both run on 4.5 volts. All you need to do is use some alligator clips to connect the spring inside the laser pointer to the negative terminal of the battery pack and connect the barrel of the laser pointer to the positive terminal of the battery pack. Then mount the laser pointer to the circuit port. The buzzer on the alarm works to alert you if you’re nearby, but you can also connect the trip wire to a larger security system to connect your laser tripwire to another circuit connect the grounds of both circuits together. Then connect the wire that was attached to the negative terminal of the buzzer to the signal input of the second circuit, for example, if you’re using an arduino wire it to a digital input, pin and use the digital read function to monitor the wire when it detects A low signal have it activate the alert system? Well, that’s how to make a laser tripwire alarm thanks for watching and check back next week for more diy hacks and how to’s .