How to create your own laser home alarm system for under $20


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Here’s a short video tutorial that will teach you how to build a cheap laser alarm system. Total cost of the project: $20. This thing may not warn the cops when burglars break into your home, but it will probably set their heart pumping and make them run away in panic from your den when its siren starts screaming into their ears.







61 Responses to How to create your own laser home alarm system for under $20

  1. Can anyone give me the complete list of the products?

    Beacuse in the video he says that we need 2 projects boxes, 1 fotocell, a transistor and so on. But he nver says what kind of fotocell, transistor, resistance, capacitor…

    Well I hope anyone can help me…

    Carlos Balanzario

    • Here is the list for you Carlos:

      -2 small project boxes

      -1 1000uF 35v Capacitor

      -1 5K Variable Resistor

      -Photocell

      -IC Board

      -9v battery and clip

      -1 N3904 Transistor

      -Toggle switch

      -Small mirrors

      -HandiTak

      -12v DC Piezo Siren – 102dB

      -Aixiz 650nm 5mw 12X30mm laser

      -Aixiz 3.2v AC Adapter

  2. Can anyone give me the complete list of the products?
    Beacuse in the video he says that we need 2 projects boxes, 1 fotocell, a transistor and so on. But he nver says what kind of fotocell, transistor, resistance, capacitor…

    Well I hope anyone can help me…

    Carlos Balanzario

    • Here is the list for you Carlos:

      -2 small project boxes
      -1 1000uF 35v Capacitor
      -1 5K Variable Resistor
      -Photocell
      -IC Board
      -9v battery and clip
      -1 N3904 Transistor
      -Toggle switch
      -Small mirrors
      -HandiTak
      -12v DC Piezo Siren – 102dB
      -Aixiz 650nm 5mw 12X30mm laser
      -Aixiz 3.2v AC Adapter

      • how is it all hooked up I don’t have a lot of knowledge in this area. does the 2n3904 have to be a certain way ? and so on. I could use some help in this area.

      • I found all of this at radioshack. Any idea what are the catalog numbers i need? Also, I’m not very good at reading the sketch or skematic, any extra help?

  3. Does anyone know how to make a counter so that whenever th beam is broken, the counter counts it once?

  4. Does anyone know how to make a counter so that whenever th beam is broken, the counter counts it once?

  5. yea don't ask at radio shack. they got the goods, but nobody in there knows a damn thing. if somebody from hackaday.com was on their staff, i'd be in that store much more frequently

  6. yea don’t ask at radio shack. they got the goods, but nobody in there knows a damn thing. if somebody from hackaday.com was on their staff, i’d be in that store much more frequently

  7. hey i guys was looking for this laser alarm to set up when i go camping . I like to know when bears are in the area. The alarm i seen a few months back is a little easier than the one above. IT used a personal alarm, laser, and night-light with the photo sensor. ( all can be found at my local dollar store )…

    THE problem with this is, its plug into the wall for a power supply. I need it portable.

    someone with a little electronc experance could figure out to step down the power for the night light it should work … any ideal emailmail me thanks alexjr8888@hotmail.com

  8. hey i guys was looking for this laser alarm to set up when i go camping . I like to know when bears are in the area. The alarm i seen a few months back is a little easier than the one above. IT used a personal alarm, laser, and night-light with the photo sensor. ( all can be found at my local dollar store )…

    THE problem with this is, its plug into the wall for a power supply. I need it portable.

    someone with a little electronc experance could figure out to step down the power for the night light it should work … any ideal emailmail me thanks alexjr8888@hotmail.com

  9. I would like to use this in my friends store to welcome and alert of customers but i just want it to go off once and with my own greeting.

  10. I would like to use this in my friends store to welcome and alert of customers but i just want it to go off once and with my own greeting.

  11. I would like to ask, if u cut the laser beam, the alarm rang rite, if u remove your hand, does it still rang?

  12. Yea, this is cool, but I need something you can find in your household for some components. I live in Serbia so I cant find all this stuff in stores. This is what I got:

    - Red Laser
    - 1 Project box

    can someone suggest stuff you can find in your house? plz?

  13. Yea, this is cool, but I need something you can find in your household for some components. I live in Serbia so I cant find all this stuff in stores. This is what I got:

    - Red Laser

    - 1 Project box

    can someone suggest stuff you can find in your house? plz?

  14. it is a very nice little project and i would like to make one like this and from this momment i will try this brilliant idea :D:D

  15. it is a very nice little project and i would like to make one like this and from this momment i will try this brilliant idea :D:D

  16. i need help hooking up the circuit i followed the schematic, but still can't get it to work. Could someone explain why the transistor is needed specifically in this circuit?

  17. i need help hooking up the circuit i followed the schematic, but still can’t get it to work. Could someone explain why the transistor is needed specifically in this circuit?

  18. Yeah, can anyone answer my questions. I have the circuit wired all up but doesn't work. Once I connected it to the 9V battery, the alarm immediate went off. To my understanding, it should go off when the laser light is broken. My questions are listed below?

    1. where the base of transistor is wired to? To the positive of 9V battery and 5k variable resistor?

    2.There are three leads(legs) on variable resistor, which two are wired to the positive of 9v battery(which is the same point as wired to the base of transistor)?

    3. where the collector of transistor is wired to? To the negative of 12V DC Sire and the negative of 1000uF capacitor?

    4. What type of photocell is the right kind? Can it be different kind or it has to be exact the same as it is shown in the video? If it is so, where to order one?

    5. How about the value of the variable resistor? I have 100K variable resistor that I used, is it a problem?

  19. Yeah, can anyone answer my questions. I have the circuit wired all up but doesn’t work. Once I connected it to the 9V battery, the alarm immediate went off. To my understanding, it should go off when the laser light is broken. My questions are listed below?

    1. where the base of transistor is wired to? To the positive of 9V battery and 5k variable resistor?
    2.There are three leads(legs) on variable resistor, which two are wired to the positive of 9v battery(which is the same point as wired to the base of transistor)?
    3. where the collector of transistor is wired to? To the negative of 12V DC Sire and the negative of 1000uF capacitor?
    4. What type of photocell is the right kind? Can it be different kind or it has to be exact the same as it is shown in the video? If it is so, where to order one?
    5. How about the value of the variable resistor? I have 100K variable resistor that I used, is it a problem?

  20. Is anybody able to answer my questions which I have posted them on 6/13? I really would appreciate. I'm having troubles to get it working.

    • 1. where the base of transistor is wired to? To the positive of 9V battery and 5k variable resistor?

      Looks like the base of the transistor is wired to the positive +9V. The negative terminal of the battery is ground. the 5k variable is connected on one end to the +9V and the photocell on the other end. The middle lead (the wiper) is connected to the +9V as well.

      2.There are three leads(legs) on variable resistor, which two are wired to the positive of 9v battery(which is the same point as wired to the base of transistor)?

      See above.

      3. where the collector of transistor is wired to? To the negative of 12V DC Sire and the negative of 1000uF capacitor?

      Yes. The capacitor and siren are in parallel.

      4. What type of photocell is the right kind? Can it be different kind or it has to be exact the same as it is shown in the video? If it is so, where to order one?

      Not sure what kind of photocell in the video. It looks pretty small. Ask for a mini photocell (1k light resistance/10k dark resistance).

      5. How about the value of the variable resistor? I have 100K variable resistor that I used, is it a problem?

      Yes. Use a 5k. Remember to vary the resistor if the alarm goes off. You can try varying the 100k but it might be too sensitive.

  21. Is anybody able to answer my questions which I have posted them on 6/13? I really would appreciate. I’m having troubles to get it working.

    • 1. where the base of transistor is wired to? To the positive of 9V battery and 5k variable resistor?

      Looks like the base of the transistor is wired to the positive +9V. The negative terminal of the battery is ground. the 5k variable is connected on one end to the +9V and the photocell on the other end. The middle lead (the wiper) is connected to the +9V as well.

      2.There are three leads(legs) on variable resistor, which two are wired to the positive of 9v battery(which is the same point as wired to the base of transistor)?

      See above.

      3. where the collector of transistor is wired to? To the negative of 12V DC Sire and the negative of 1000uF capacitor?

      Yes. The capacitor and siren are in parallel.

      4. What type of photocell is the right kind? Can it be different kind or it has to be exact the same as it is shown in the video? If it is so, where to order one?

      Not sure what kind of photocell in the video. It looks pretty small. Ask for a mini photocell (1k light resistance/10k dark resistance).

      5. How about the value of the variable resistor? I have 100K variable resistor that I used, is it a problem?

      Yes. Use a 5k. Remember to vary the resistor if the alarm goes off. You can try varying the 100k but it might be too sensitive.

  22. ROFLMAO…………um…………I will never be able to make that. Can you just send the site to me of where I can buy that? lol

  23. ROFLMAO…………um…………I will never be able to make that. Can you just send the site to me of where I can buy that? lol

  24. I’m going to make a laser base security system.but the problem is it must work all ina day.so i must find good laser source and photodiode or phototransistor or LDR for that.cost is not mention. i just need good quality parts. laser beam must go 40 feet without reducing its intensity and using sensor i want to get a pulse when laser beam cut.can you help me to find these laser source and sensor.

  25. I'm going to make a laser base security system.but the problem is it must work all ina day.so i must find good laser source and photodiode or phototransistor or LDR for that.cost is not mention. i just need good quality parts. laser beam must go 40 feet without reducing its intensity and using sensor i want to get a pulse when laser beam cut.can you help me to find these laser source and sensor.

  26. i would like to build a computerized alarm system that sends an sms where there is an intruder but i have no idea, help guys