Laser Tripwire

When I first started trying to figure out how to build a tripwire i was able to find a lot of different ways to do it but they each had their flaws. Some were too complex, requiring ICs or Arduino. Some were simple but only stayed on while the beam was broken. Finally after experimenting with a variety of methods I came up with a simple laser tripwire that stayed on when the beam was broken.

Step 1 Materials

What You need:
4 100 ohm resistors
1 switching diode
3 transistors. I used 2n2222 but anything similar will work
1 photoresistor (LDR)
1 buzzer. you can also substitute an LED or anything else you want the Tripwire to set off

You will also need a breadboard, jumpers and a laser pointer for assembly

Sorry for the poor quality picture

Comments

[evilgenius32]

DUDE!!! Awesome 'ible Made one myself but I had some problems. I put it together and it only stayed onn when the beam was broken. I was wondering what transistors you used and if you used different ones for each switch. Thanks for the ible again!

[phantomboy]

I used 2n2222 transistors for all the parts. You can use other NPN bipolar transistors instead as long as the power ratings are similar.

[bakinkoljach]

Why is so important to all transistor have similar power rating?
i used BC107A 240hfe ,BC107B 400hfe and BF182B 240hfe it does not work at all no Volts at buzzer at any time,and can i use cutted 2N3055 as solar cell instead of photo resistors?

[evilgenius32]

Thanks, thats what I'm using. But do you have any ideas on why it won't stay on?

[phantomboy]

I have had this problem before but am still not 100 percent sure why it hapens. I would double check to make sure that the transistors are connected correctly with the emitters conected to ground. Sorry I cant be of more help.

[evilgenius32]

Thanks anyway. Awesome Ible still, too bad I couldn't get it to work. :(

[vishalapr]

Absolute brilliant!Rated 5*!Really cool!
Have a look at my ibles as well!