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Electronics GCSE Alarm Circuit.

Discussion in 'Modding' started by Mr_Meeker, 5 Jan 2005.

  1. Mr_Meeker

    Mr_Meeker What's a Dremel?

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    Hihi,

    I would appreciate it if somebody could design me a simple door alarm circuit for my GCSE alarm project.
    I'm useless at it and could do with the help, it is mainly to incorporate a reed switch/555 timer.

    -Cheers.

    (I'll be back home later for more info)

    PS- I also need to be able to design it on crocodile clips, unless someone else fancies having a go for me ofcourse ;)
     
    Last edited: 5 Jan 2005
  2. Murdoc

    Murdoc Gas Mask..ZOMG

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    Ya know why they give you this coursework to do? It counts towards your grade, your meant to do it, not bit-tech members, I don't mind helping in fact I enjoy it.

    'doc
     
  3. bigal

    bigal Fetch n Execute

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    well the complexaty of this could vary alot. reedwsitchs are NC yeah?

    555 timer would be used on output stage to produce a pulsating beep from a buzzer. you could use an inverter via the reed switch to do this. Incorpirate a "Thrysistor" to make it latching. (i used them in year 9 at my school..)

    all sorts of possibilities. :)
     
  4. Mr_Meeker

    Mr_Meeker What's a Dremel?

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    Right that was a bit brief as i was doing it towards the end of my lesson.

    reply #1:

    It does not matter where you get the circuit from, afaik only one or two people in my year have designed their own circuit, as long as you have something to start with your fine to get it from where you want.

    Reply #2:

    It basically needs to be an alarm thats stuck onto a door or whatever, and whenever its opened the reed switch opens and the alarm is triggered.

    This is just about as far as i know, anything simple that could work would be highly appreciated, i can always get help at school but im just not interested in electronics myself and its a subject which i didnt choose in the first place so i just need a push to get going :/

    Anything that people could suggest would be great.
     
  5. Murdoc

    Murdoc Gas Mask..ZOMG

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    When I did GCSE electronics 3 years ago, we had to research what we were going to do, find multiple circuits or start from scratch then modify it to our needs. Asking someone to design the circuit is not something they aproved of and when we handed the coursework in we had to sign to say we had not done so. Maybe it has changed?
    Anyway I don't wish to screw your thread up so I will shut-up now.

    'doc

    EDIT: Big al has the idea most people used, you should have some form of notes on thyristors, iirc you need 3 stages for it to qualify, or is this also different?
     
  6. bigal

    bigal Fetch n Execute

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    Just to add a bit more, a thrysistor is a TO92 package device (looks just like a transistor) with three legs, Collector, emmitor and base. It works in the same way as a transistor BUT..... it is not a transistor :duh: It latches.

    thus when the reed opens, you somehow invert the state, so a line goes high, activating the thrysistor, activiating a Transistor (cant remember how much a thrysistor can sink - we just used them for a shakey hand game to lock the LED on till you pushed reset (which basically cycled the power to reset the thrysistor (turns power off then on again)) then into a relay working a banging loud bell :D sorted...


    EDIT...
    or the line from the transistor goes to a dead simple 555 osc circuit working at about 1hz to buzz a hell loud buzzer. :D

    either way it has gotta be defaning... 1st rule of alarms..
     
  7. Murdoc

    Murdoc Gas Mask..ZOMG

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    Ooooh set a speaker up with an Astable at the frequency of brown noise, make em p00 themselves

    /child

    'doc
     
  8. Hazchem

    Hazchem Minimodder

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    only one or two people designed their own circuits? I'm doing gcse electronics now and everyone doing it has designed their own circuit using crocodile clips and pcb wizard.
     
  9. cpemma

    cpemma Ecky thump

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    Is that measured in Fartz? :hehe: :hehe: :hehe: :blush:
     
  10. c.cam108

    c.cam108 Minimodder

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    Groan @ Acrim!

    What is the frequency of brown noise anyway? I have alwas wanted to know. :evilgrin:

    _C
     
  11. c.cam108

    c.cam108 Minimodder

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    Doesn't matter, I found out. It's between 10.5 and 16 Hz. :naughty:

    /me thinks of uses.....

    _C
     
  12. ChromeX

    ChromeX Minimodder

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    They did this on brainiac: science abuse didnt they they found it to be the frequency at which the sphincter muscles contract, so find that and build a circuit that emmits that frequency and leave it some where :thumb:
     
  13. Murdoc

    Murdoc Gas Mask..ZOMG

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    No need when I have just got my hands on a nice Gould function generator, their will be a thread up soon, as not to trash this one on my progress, yes cpemma that will be the unit of measurment...

    'doc

    EDIT : http://forums.bit-tech.net/showthread.php?p=841651#post841651
     
    Last edited: 6 Jan 2005
  14. Mr_Meeker

    Mr_Meeker What's a Dremel?

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    Yup, we dont have to do any designing as far as weve been told as my teachers just said get it off a GCSE website or whatever, but being the useless fecker i am i can neither design nor find this extremely simple circuit ;)

    We do however have to build/print it in crocodile clips but it doesnt matter where you get it from...
     
  15. Snood

    Snood What's a Dremel?

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    you do realise that asking for this sort of help is completely against the eam board rules and would be classed as cheating...... and really.... if you are doing GCSE electronics, you really should know how do to an alarm... i mean really..... how basic.. just bare in mind that if any exam board catches sight of this you could get grades for all your courses through that board canceled.

    Snood
     
  16. Springs

    Springs Boing boing

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    i did my GCSE's about 1 or 2 years ago and we had to research similar devices and then design/build one our selves me and a couple of friends used crocodile clips to design ours.. and at the end of it all we had to sign the coursework to say that it was all our own work and didnt steal anything...etc etc...

    its not hard to make an alarm that triggers when a connection is broken..
     
  17. bigal

    bigal Fetch n Execute

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    you could just wire up a DPDT relay so it latches and the latch is broken when the wire is cut, but that is probaly too simple, more electrical than electronic. :eyebrow:
     

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