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This is one of the common projects made using lasers .its cheap ,reliable ,safe and most important of them all handy to protect all your things.

Step 1: Materials

according to the image
1 photocell or LSR or LDR (as you call it) x1
2 5k variable resister x1
3 2n3904 transistor x1
4 1000uf 35v capacitor x3
5 speaker
6 9v battery x1
7 button cells x4
8  9v battery clip x1
9 most important of them all laser diode
10 vero board or circuit board

Step 2: Solder It Up

solder all components and ensure that all the capacitors are arranged in series and not in parallel and this is how it should look like
 The 9v supply is for the circuit and  4 button cells  for the laser diode
you could use duct tape to secure the switch of your laser diode




have loads of fun!!!!!!!!!!!!!!!!!!!
This has to be one of the worst explained instructables i have ever seen. it makes it very difficult for new people to electronics who dont have a great knowledge of reading schematics .and for those who do it lacks detail <br>
U say variable resistor but i cant see it on your image of alarm
<p>what is the exact specification of :</p><p>2n3904 transistor</p><p>button cells</p><p>laser diode</p>
<p>Can i use more than one laser diode and LDR in this circuit for more security?</p>
<p>hey can it be done by 2 capcitors</p>
i haven't tried that but i think it should work<br>
how to switch it on ??
can u give me the place to purchase the materials ? <br>i want cash on delivery
If I use a 12v lead-acid rechargeable battery on that (for renewable power), which components should I change? And what are the specs of the new components? Many thanks in advance.
12v battery gives large ampereage which will easily damage your transistor <br>
I just want to know that you have asked for 3 capacitors and had mentioned only one in schematic diagram.Do all the capacitors share same legs and if yes why didn't you used a single equivalent capacitor.
well i could not find a cap of that rating so i used this ,all of them have not been attached since it worked well with 1 <br>
I was thinkin abt making an instructable of the same thing, but mine has a latching circuit that latches the alarm so it will keep on ringing until it is reseted. Haha good job!
Please send me the circuit diagram of your circuit to me : abdu.mastermind@gmail.com . <br> <br>It would be of great help...thanks in advance
I will as soon as I can
good job dude happy to know that someone improved it
Did anyone try it and did it work<br>
did you see the LASER DIODE any where? <br>did you also see the Silver Oxide battery, for the Laser diode?

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