Burglar Alarm homework help

Discussion in 'Homework Help' started by michael_9, Apr 4, 2015.

  1. michael_9

    Thread Starter New Member

    Apr 4, 2015
    5
    0
    Hello i am new here but i am having a hard time with some questions if you can please help me. And by the way the circuit should be using CMOS 4011 logic gates.
    1. Explain, in general terms, how the burglar alarm works.
    2. Draw a neat circuit diagram for the burglar alarm. (Including a Buzzer & a transistor)
    3. Explain the purpose of the pull down resistors.(connected to the switches)
    4. Explain why unused NAND gates have their inputs connected high.
    5. Explain why the transistor was needed when we switched from an LED to a buzzer.
    6. Explain why we needed to add resistors to the circuit when we added the light dependent resistor (LDR) to detect the laser beam.
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,446
    3,362
    Your query is incomplete.
    What burglar alarm are we referring to?
    Is there a circuit diagram that should accompany your query?
     
  3. michael_9

    Thread Starter New Member

    Apr 4, 2015
    5
    0
    Do you want the breadboard diagram?
     
  4. MrChips

    Moderator

    Oct 2, 2009
    12,446
    3,362
    A circuit schematic.
     
  5. michael_9

    Thread Starter New Member

    Apr 4, 2015
    5
    0
    ok this is what i think it is:
     
  6. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    In your circuit it is not clear how the transistor is connected.
    Also it is not clear how the buzzer is connected.

    You also must give a try to answer the query you gave.
    That way we can see if you understand the query.

    Bertus
     
  7. michael_9

    Thread Starter New Member

    Apr 4, 2015
    5
    0
    how would you draw a burglar alarm. because when you activate the first switch the alarm goes off and if you turn it off i stays on until you use a different switch which is the reset switch.
     
  8. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    It is your assignment.
    The transistor can not be towards the outputs of the gates with the E and C.
    The base should be connected to one of the outputs with a current limiting resistor.

    Bertus
     
  9. michael_9

    Thread Starter New Member

    Apr 4, 2015
    5
    0
    [QUOTE[​IMG]="bertus, post: 841284, member[​IMG]: 20420"]Hello,

    In your circuit it is not clear how the transistor is connected[​IMG].
    Also it is not clear how the buzzer is connected[​IMG]
    You also must give a try to answer[​IMG] the query you gave.
    That way we can see if you understand the query.

    Bertus[/QUOTE[​IMG]]
    how would you make it? i have a clue of how it works: one of the swithces is activated so the alarm goes of (buzzer) the if you switch it off the alarm still goes off, so the only way to reset it is to have a swith that is the reset swith that when you switch it on it resets the swith.
     
  10. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
  11. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,159
    And why does the alarm remain energized when you activate the first switch?

    You might as well send a picture of your breadboard as your schematic no way resembles it.
     
  12. dl324

    Distinguished Member

    Mar 30, 2015
    3,248
    624
    Hi Michael_9,

    You didn't explain how the alarm is supposed to work. You have an LDR (though it's typically a two terminal device) in your circuit and you mention a laser beam in your last bullet; are there multiple schematics for this problem?
     
  13. WBahn

    Moderator

    Mar 31, 2012
    17,754
    4,799
    I'm guessing that they built up an alarm in lab on a breadboard and made some changes to it as part of the lab and then these are questions that were asked regarding that lab. The TS's rendition of the schematic is but a poor attempt at representing the final breadboarded circuit.
     
  14. MrChips

    Moderator

    Oct 2, 2009
    12,446
    3,362
    Well that seems backwards as we all know, putting the carriage before the horse.

    One draws a circuit diagram before building the circuit on a breadboard, like building a house and then drawing the plans afterwards.
     
  15. WBahn

    Moderator

    Mar 31, 2012
    17,754
    4,799
    I'm doing a lot of reading between the lines. I'm guessing that they started with a simple version, probably with a schematic, and then were told to make a few modifications to it, possibly either verbally or in prose, without a new complete schematic. They might have been given an updated portion of a schematic along with instructions like, "Now replace the LED with a buzzer by ...."
     
Loading...