Connect with us

how to make buzzer only beep once.

Discussion in 'General Electronics Discussion' started by dougy.b, Nov 6, 2011.

Scroll to continue with content
  1. dougy.b

    dougy.b

    17
    0
    Nov 6, 2011
    Hi all, this is my first post and hoping to get some advice from you knowledgeable people.

    basically i have what is known as a bite alarm (for fishing). normally bite alarms beep as the fishing line passes over a wheel which usually has notches in it to allow some sort of optical switching making it go beep-beep-beep until the wheel stops.
    however i have been given some particularly cheap alarms which quite often get stuck with the buzzer constantly on and i have to physically move the wheel to silence the buzzer.

    I have discovered that this alarm uses a reed switch with magnets on the wheel, so if the magnet gets stuck next to the reed switch the buzzer sounds constantly.

    I am hoping someone can advise me how to modify this circuit so that if the magnet does hold the reed switch closed the buzzer will only beep once.

    This is the existing circuit
    [​IMG]
    sorry for the bad drawing

    Thanks in advance.

    Doug
     
  2. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    Hi, welcome to this forum!

    You can use a so called one-shot circuit to achieve that.

    See my little sketch.


    The datasheet ot the used componant is here:

    http://www.bucek.name/pdf/4528.pdf

    The unused monostable pin's are to connected as on fig10

    I keep the "odd" connection of you led + buzzer at the transistor collector.

    The bip duration is defined by the 1Mohms/100nF cell, to be adjusted to your needs.

    Olivier
     

    Attached Files:

  3. dougy.b

    dougy.b

    17
    0
    Nov 6, 2011
    Hi Olivier, thanks for the warm welcome.

    I shall check my box of goodies and see if i have the components.

    Thanks for your help.

    Doug
     
  4. dougy.b

    dougy.b

    17
    0
    Nov 6, 2011
    Hi again,

    I was just wondering if it would be at all possible to use a 7412 (sn74121n) in place of the 4528? (as i have one of those in my component box)
    please feel free to give me a slap if I'm completely off the mark here (my electronics knowledge is very limited)

    sorry
    Doug
     
  5. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    Hi Doug,

    The 74121 is indeed functionally equivalent to the 4528 (no slap so :) ) . But he is not a CMOS type, mean he will draw more current from your batteries, better to go for a cd4528 or 4538 so!

    Olivier
     
  6. sheldonstv

    sheldonstv

    68
    0
    Jul 17, 2007
    Heres a schematic you can use

    [​IMG]

    [​IMG]
     

    Attached Files:

  7. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    Dear sheldonstv,

    The first schematic is useless as the OP as drawed a reed switch as trigering element, no inverting function for the set/reset available so, moreover it's just a flip-flop, no temporisation available.

    The second schematic is also useless as he is 12 volts powerd where only 4.5 volts are availables (3 button cells). Even redesigned for 4,5V (knowing this is the lower limit of the 555 supply) it' s overkill for such simple function. Also the FET is 4.5 Amp rated where the supply is build around tinies button cells...

    Olivier
     
    Last edited: Nov 8, 2011
  8. sheldonstv

    sheldonstv

    68
    0
    Jul 17, 2007
    errrrrmmm yes thatt is quite right......i need a fresh pair of glasses
     
  9. dougy.b

    dougy.b

    17
    0
    Nov 6, 2011
    thanks for the input anyway sheldon.

    i shall go for the 4528/4538 circuit.

    thanks very much everyone.
     
  10. KMoffett

    KMoffett

    723
    75
    Jan 21, 2009
    A relative simple solution with passive components. The buzzer will beep and the LED will flash momentarily as the magnet passes the reed switch. If the magnet stops with the reed switch closed the buzzer will beep once and the LED will stay on.

    Ken
     

    Attached Files:

  11. dougy.b

    dougy.b

    17
    0
    Nov 6, 2011
    Hi, I've been away for a while. but i now have a couple of 4528 chips to hand.

    Olivier, you mention the unused monostable pins above. any chance you could spell it out for me please? i don't really understand the fig 10 diagram on the datasheet, sorry.:eek:
     
  12. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    Hi Doug,

    The figure10 apply for any of the 2 monostable. As we (arbitrarily) use the first one when mapped with the pinout, the second one connections becomes:

    PIN

    9 leave unconnected
    10 leave unconnected
    11 Go to +
    12 Grounded
    13 Go to +
    14 leave unconnected
    15 Grounded

    The pin 1 must also be grounded, what is missing on my schematic!

    Olivier
     
  13. dougy.b

    dougy.b

    17
    0
    Nov 6, 2011
    thanks so much.
    I'll let you know how I get on.
     
  14. dougy.b

    dougy.b

    17
    0
    Nov 6, 2011
    Hi again Olivier.

    I have just tried making this circuit on a bread board with no luck I'm afraid.

    please can you confirm a few things for me?
    pin 6 is NC. I've taken this to be Not Connected. am i right?
    pins 3, 5, 11, 13 go to +
    pin 1 to ground and to the capacitor
    pins 8, 12,15 and the emitter of the transistor and the 10k resistor from pin 4 to ground.

    also, am I OK to substitute the bc547 for a bc548?

    I have connected everything as it is on the diagram and with the added notes in your last post to no avail, the only difference being that i am using a bc548.

    Many thanks
    Doug
     
  15. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    Hi Doug,

    Yes I confirm the pin's connection and add pin 16 go to +
    please post sharp pictures of top and bottom of your bread board.
    BC548 is fine.

    Olivier
     
  16. dougy.b

    dougy.b

    17
    0
    Nov 6, 2011
    Hi Olivier,

    Thanks for getting back to me.
    I've taken two photos of the top for good measure,
    you can find them here: http://i135.photobucket.com/albums/q124/flatline-uk/DSCF1590.jpg
    http://i135.photobucket.com/albums/q124/flatline-uk/DSCF1589.jpg

    The bottom is not visible on these breadboards, but here's an image of how they're connected internally: http://i135.photobucket.com/albums/q124/flatline-uk/Elec_primer-breadboard2.jpg

    The two yellow wires going off to the left are for the reed switch. top left red wire = (+)positive. top right black wire = (-)negative.

    I have also left out the LED for the moment.

    Thanks for helping, i've probably messed up somewhere.
     
  17. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    Hi Doug,

    The pin 16 is not connected, must be +

    I will check the rest.

    Olivier
     
  18. dougy.b

    dougy.b

    17
    0
    Nov 6, 2011

    I think it is, row 54, 3rd hole to the right of pin 16 going up to row 51/pin 13 then to pin 11 and to +. sorry if the picture isn't very clear.

    also i'm getting 4v across the speaker as soon as the batt is connected, but it does not sound. however if i connect if straight to the 4v batt it sounds. if i connect the switch the speaker will 'click' faintly.


    Thank you so much.
     
  19. dougy.b

    dougy.b

    17
    0
    Nov 6, 2011
    Nevermind......

    I've been a complete dumbass.
    I've got the entire right hand side of the chip backwards. i've assumed pin 9 to 16 is top to bottom. but it's bottom to top.
    man i'm rusty...

    Sorry
     
  20. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    Yep that's it , few rewiring needed :eek:

    be strong !
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-