Beginner Laser or IR beam alarm system - Page 6 - Electronic Circuits Projects Diagrams Free

henhen0412 · 15th April 2008, 04:27 AM

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

mneary · 15th April 2008, 11:26 PM

You can use any small signal transistors. Examples:

NPN: 2N3904, 2N2222, MMBT4401, BC547, BC847
PNP: 2N3906, 2N2907, MMBT4403, BC556, BC557

russianbadboylb · 28th April 2008, 09:26 AM

why dont people just modefy a nightlight?

Torben · 28th April 2008, 10:08 AM

Quote:

Originally Posted by russianbadboylb

why dont people just modefy a nightlight?

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

Gayan Soyza · 28th April 2008, 11:26 AM

Quote:

Originally Posted by russianbadboylb

why dont people just modefy a nightlight?

If you look this thread you will get an idea about a LED night light.

http://www.electro-tech-online.com/e...ght-light.html

mrkedar_kyk · 31st May 2008, 09:57 AM

your project was really amazing
i like it very much.

Amarr · 23rd August 2008, 05:48 AM

http://www.freewebs.com/tentt/
this site contains some tent oriented ideas view it

tmurali · 10th September 2008, 02:03 PM

Quote:

Originally Posted by zachtheterrible

This is a cool little circuit that i made for a school project. It can be used as one of those things that is usually seen on the door of small shops so that when someone walks in it goes "ding dong". It could also be used as a burglar alarm (just need to get a loud enuf siren).

A light has to be pointed at the LDR. It can be anything, just as long as its bright enough. Im pretty sure that an infrared LED would work, a regular light, or my personal favorite: a laser pointer, just like in the movies 8) . You could encircle your house w/ a laser so wen someone crosses the beam you know.

R1 can be adjusted for sensitivity of the circuit to light. The lower R1, the more sensitive, and vica versa. The value of R1 will not allow the circuit to work in direct or indirect sunlight. R1 would have to be increased to make the circuit less sensitive to light (even then i doubt it would work in direct sunlight). An alternative to this is putting a tube on the LDR that is a couple centimeters long so that only light from the light source could get in.

R4 can be adjusted for how long the buzzer stays on. 100k makes it stay on for about 9 seconds. Or the value of C1 could be adjusted.

Someday i plan on putting a transmitter on the circuit so that it could be put out in the yard, and a receiver inside would go off. HAVE FUN :lol:

could you give the values of pnp and npn's

henok · 14th October 2008, 11:12 AM

what is the value of the transistors

henok · 14th October 2008, 11:21 AM

hi how are you i am from ethiopia & i am electronics student .
i really need to know the values of the transistors.

slamslam123 · 15th October 2008, 09:10 PM

hi guys . if any person has information about the voice over power line, please give it to me

blueroomelectronics · 15th October 2008, 10:17 PM

Quote:

Originally Posted by henok

hi how are you i am from ethiopia & i am electronics student .
i really need to know the values of the transistors.

Page 2 of the thread.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Title	Starter	Forum	Replies	Latest
laser beam-break detector	Darth Bagel	Electronic Projects Design/Ideas/Reviews	9	15th November 2008 04:33 AM
Beam alarm system	zachtheterrible	Electronic Projects Design/Ideas/Reviews	31	25th September 2008 11:32 AM
Building IR BEAM Break alarm system	damenace	Electronic Projects Design/Ideas/Reviews	3	31st May 2008 09:44 PM
laser alarm system	ira thakur	Electronic Projects Design/Ideas/Reviews	8	9th January 2008 03:11 AM
Laser Beam Tachometer With Pic	iftikhar ahmed	Micro Controllers	7	10th February 2007 02:38 PM

15th April 2008, 04:27 AM	(permalink)
henhen0412	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

15th April 2008, 11:26 PM	(permalink)
mneary	You can use any small signal transistors. Examples: NPN: 2N3904, 2N2222, MMBT4401, BC547, BC847 PNP: 2N3906, 2N2907, MMBT4403, BC556, BC557

28th April 2008, 09:26 AM	(permalink)
russianbadboylb	why dont people just modefy a nightlight?

31st May 2008, 09:57 AM	(permalink)
mrkedar_kyk	as..... ordinary your project was really amazing i like it very much.

23rd August 2008, 05:48 AM	(permalink)
Amarr	http://www.freewebs.com/tentt/ this site contains some tent oriented ideas view it

14th October 2008, 11:12 AM	(permalink)
henok	what is the value of the transistors

14th October 2008, 11:21 AM	(permalink)
henok	hello hi how are you i am from ethiopia & i am electronics student . i really need to know the values of the transistors.

15th October 2008, 09:10 PM	(permalink)
slamslam123	power line communication hi guys . if any person has information about the voice over power line, please give it to me