Laser or IR beam alarm system

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pesonal alarm

Would it be possible to place one of these 110db personal alarms instead of the buzzer by connecting the two wires that would normally go to and from the buzzer and connecting them to the battery terminals on the personal alarm, or would i have to modify the circut in any way (different resistor hm: , different placement, etc.)
 
can u give me the circuit diagram.i would like to build up one of those.
this my email-id -lurkingdevil@gmail.com .Also please tell me how to keep it on for some time if u fugured it out.thx
 
there is another way to build a circut, just have a battery connected to a photocell holding up a nail with an electromagnet, than, if the laser stops, the nail drops and completes another circut that triggers an alarm
 
what is the part of the circuit that controls how long it stays on? i am hoping to make this circuit with only a capacitor, a transistor, a photocell, and a resistor, but i need to know how to make it stay on for 10 seconds. i dont need the circuit, im just wondering if this will work.
 

can i have the circuit to? heres my email- dak0ta1@hotmail.com
 
Plz Get ThE OpErATioN aND cOnstructiOn Of ThIS cIRCuit.

Hey...this is a gud circuit ... Actually it would be nice if I get the theory, construction and the design of this circuit. Pls get me with the same.
 
NiniPoojaSheeja said:
Hey...this is a gud circuit ... Actually it would be nice if I get the theory, construction and the design of this circuit. Pls get me with the same.
Click to expand...

All I saw was this.

**broken link removed**
 
Hi, does anyone had a schematic for IR sensor? i want to hook it to my game controller so i need IR so that it would be invisible when i struck it. tnx~
 
hay i am trying to make your gadget but i need the codes for the 4 transistors on this design could you tell me the codes
 
hay crumlink i need to make a laser alarm for a school project but the circuit diagram here does not give the code for the trasistors can you give it to me or do you have a new design that i could follow please reply now
 
You can use any small signal transistors. Examples:

NPN: 2N3904, 2N2222, MMBT4401, BC547, BC847
PNP: 2N3906, 2N2907, MMBT4403, BC556, BC557
 
russianbadboylb said:
why dont people just modefy a nightlight?
Click to expand...

Mains voltage isn't required to solve the problem, and night lights use mains voltage. Why mess with it if you don't have to? It's simpler to do using a photodiode or phototransistor, a transistor or two, and a 555, or even a microcontroller. Almost any microcontroller you could name would actually be serious overkill unless you wanted to add some features.

Other problems with using a night light:

  • They're slow. Night lights use LDRs (light-dependent resistors) which have a response time which might be a problem, depending on the speed of the target.
  • Designing your own, i.e. using a 555, lets you control more things, such as how long the alarm signal lasts. With a night light as the trigger, you would have to design a system (possibly using a 555) to control how long the alarm lasts. If you didn't, your buzzer would only buzz while the beam was actually interrupted. Somebody just walking through it would make it go "BZ" for less than a second. Using something like a 555 you could make it buzz for, say, 5 seconds.

While you could probably make a working alarm circuit from a night light, in short, it would be a) dangerous, and b) slow.


Torben
 
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