Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Mock burglar system. Infrared.

  1. Nov 24, 2011 #1
    Hello everyone,

    I have a project in science and I am puzzled with something. I want to have and IR emitter and an IR detector to act as a burglar alarm that will activate lights and a speaker-like thing. The only problem is that the IR set that I am using opens the circuit until it gets enough IR light then it will close the circuit and allow the charges to activate. However I want the system to activate when the flow of light is stopped. Is there any way to do this?

    Thank you very much.
     
  2. jcsd
  3. Nov 24, 2011 #2

    Averagesupernova

    User Avatar
    Science Advisor
    Gold Member

    Lets find out a bit more about your project. What kind of alarm/buzzer/indicator/etc. do you plan to use? Are you familiar with relays? This can most certainly be done, just would like to know more about your project in order to determine the best way to go about it.
     
  4. Nov 24, 2011 #3
    Thank you very much for replying.

    To start off I will just say that I only know the very basics although I am very eager to learn.

    For the sound I haven't decided on anything in particular I was just planning on using a simple noise maker. (I'm sorry I can't be more specific.)

    The plan is to have the Ir emitter/detector pair sitting on either side of a door/opening and they would be connected to a battery and the rest of the circuit. The lights and sound maker don't have and restrictions although the maximum amount of voltage I can use is 9v and it has to come from one power source.

    Thanks again for your reply.
     
  5. Nov 24, 2011 #4

    davenn

    User Avatar
    Science Advisor
    Gold Member

    hi Hoogaloo

    show us the circuit you are currently using
    modifications will probably be pretty straight forward.
    I assume you want the indicator/alarm to activate when the IR beam is broken ?
    thats the normal way

    Dave
     
  6. Nov 24, 2011 #5
    How do I show you the circuit? I only have a pencil drawing for the plan.

    And yeah I want the circuit to activate then the beam is broken.

    Thanks.
     
  7. Nov 24, 2011 #6

    davenn

    User Avatar
    Science Advisor
    Gold Member

    I use paintbrush in windows to draw circuits save them as a GIF file then up load them to various forums etc

    here's a drawing I did for another person within the last few weeks
    it will give you the basics on where to start

    attachment.php?attachmentid=41222&stc=1&d=1322189466.gif

    the trimpot can be used to adj the sensitivity

    Using the NC ( Normally Closed ) contacts of a relay means they will be open whilst the relay is energised as the circuit gets an IR beam into the sensor.
    When the beam breaks the relay will de-energise and the contacts will close and whatever alarm / lights you have in the relay circuit will get voltage via the relay contacts and operate

    cheers
    Dave
     

    Attached Files:

  8. Nov 24, 2011 #7

    davenn

    User Avatar
    Science Advisor
    Gold Member

    Now if you wanted the alarm bells / buzzer / lights to run off higher voltage then a minor mod to the relay contacts wiring would cater for that :)

    D
     
  9. Nov 24, 2011 #8

    DaveC426913

    User Avatar
    Gold Member

    I suspect that the OP does not have the level of detail of actual circuit diagrams. He is expressing his project on a much higher conceptual level.
     
  10. Nov 24, 2011 #9
    I'm sorry, I'm kind of confused. I tried to find a way I could draw out the circuit but I couldn't find an easy way it always looked really weird. I'm sorry! Is there any other way I could help explain?
     
  11. Nov 24, 2011 #10

    davenn

    User Avatar
    Science Advisor
    Gold Member

    ok no probs :)

    draw it out neatly on paper and take a sharp/clear photo of it with your phone camera etc :) let us know when you have done that and we can talk you through uploading the pic
    do you know how to resize a pic on your pc ? off the phone it will be huge 1000 or so pixels x 1000 or so pixels you want to get that down to 640 x 480 or similar size

    Dave

    PS DaveC .... Im getting sooo peved off having to relog in every 5 minutes
    I cleared all the cookies even restarted the puter and still its happening
     
    Last edited: Nov 24, 2011
  12. Nov 24, 2011 #11
    640.gif

    There is my drawing sorry if it is not very clear I can try to explain things there if you need.
     
  13. Nov 24, 2011 #12

    davenn

    User Avatar
    Science Advisor
    Gold Member

    thats a good clear drawing well done :)

    unfortunately tho making a system work isnt quite as easy as that
    it does need something along the lines of the circuit I showed you in my other post

    Do you have the electronics background for building a circuit like I showed you ?
    or...
    Do you have an electronics mate that could build it for you and help you get it working ?

    Dave
     
  14. Nov 24, 2011 #13
    Unfortunately I do not have any connections to someone with any electronics skills. I am sorry for my lack of experience. Do you still think you could help?

    Edit: Signing off for tonight Thank you for your interest guys!
     
    Last edited: Nov 24, 2011
  15. Nov 26, 2011 #14
    Still need a way to make this circuit work could anyone point me to an easy solution?

    Edit: What parts will I need?
     
  16. Nov 26, 2011 #15

    dlgoff

    User Avatar
    Science Advisor
    Gold Member

    I think a better approach would be to use a passive infrared sensor (PIR sensor).

    These are typical of intruder alarm systems:

    Front-Fresnel_type.JPG

    Regards
     
  17. Nov 26, 2011 #16
    Where do you think I could find one of those to buy? How to those work? Do they complete the circuit when it senses something in front of it?
     
  18. Nov 27, 2011 #17

    dlgoff

    User Avatar
    Science Advisor
    Gold Member

    You can purchase a variety of types from The Home Depot. This one is for $39. Do a google search on "buying motion sensor" and you'll get lots of hits.

    http://en.wikipedia.org/wiki/Motion_sensors
     
  19. Nov 27, 2011 #18
    Last edited by a moderator: May 5, 2017
  20. Nov 27, 2011 #19

    dlgoff

    User Avatar
    Science Advisor
    Gold Member

    Okay. Then:

     
    Last edited by a moderator: May 5, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Mock burglar system. Infrared.
  1. IR burglar alarm (Replies: 4)

  2. Infrared detection (Replies: 0)

  3. Infrared scopes (Replies: 14)

Loading...