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Please help with replacing electromagnetic buzzer

Discussion in 'General Electronics Discussion' started by Juzzac, Mar 1, 2015.

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  1. Juzzac

    Juzzac

    6
    0
    Mar 1, 2015
    Hi,
    I am trying to help a friend out with changing a electromagnetic buzzer from a 2700khz to 400hz or at least a much lower tone as he is hearing impaired and can't hear high frequency at all.
    Basically this is fitted in his new cars reverse parking warning system, it is a factory fitted kit and works very well except he can't hear it.
    I have found it very difficult to find a replacement buzzer in this low voltage with a lower frequency

    The specs on the original buzzer are
    Type  YC-9035S-03
    Rated Voltage  3.6Vp-p
    Operating voltage  2.5~4.5Vp-p
    Rated current  Max 100mA
    Coil resistance  16±3Ω
    Rated Frequency  2731Hz
    Sound output  Min 85dB

    I have tried two different buzzers with the specs below but get no sound from them when connected to this circuit

    Part number MCKPMB-G2603LA-K4111
    Type Mechanical buzzer
    Rated voltage : 3 V dc
    Operating voltage : 2 to 4 V dc
    Maximum rated current : 30 mA / 3 V dc
    Minimum sound pressure level : 75 dB / 20 cm
    Resonant frequency : 400 ±100 Hz
    Response time : 50 ms

    Does anyone have any ideas why i am getting no sound ??

    Any help is greatly appreciated


    Thanks Justin
     
  2. duke37

    duke37

    5,360
    765
    Jan 9, 2011
    The first buzzer looks like a speaker, it takes AC since the voltage is specified p/p.

    The second runs on DC, try this on a 3V battery (two 1.5V cells).

    You may be able to use the DC buzzer if you run the AC supply through a bridge rectifier and smooth with a capacitor but the voltage may be too low.
     
  3. KTW

    KTW

    273
    15
    Feb 22, 2015
    Did you try it from a different 3v power supply to see if it works?
     
  4. Juzzac

    Juzzac

    6
    0
    Mar 1, 2015
    G'Day Duke37 & KTW, Thanks so much for your help, it makes sense now, it seems near impossible to find that voltage and frequency i want in a AC buzzer, How to I connect the Bridge rectifier and capacitor to the buzzer??
    I tested with 3v DC and the buzzers work fine
    Thanks again for all your help mate.
     
  5. KTW

    KTW

    273
    15
    Feb 22, 2015
    Does the connection at the original buzzer have 3vdc when activated?

    3.6 voltage peak to peak should be 7.2 volts.
     
    Last edited: Mar 2, 2015
  6. KTW

    KTW

    273
    15
    Feb 22, 2015
    It would look like this
    [​IMG]
     
  7. duke37

    duke37

    5,360
    765
    Jan 9, 2011
    I think not, 3.6V will be the range of the voltage, peak to peak.

    The diagram in #6 may work but will put DC through the supply. This may or may not cause problems.
    I suggested a bridge rectifier which will not put DC through the supply but has an extra diode voltage drop which also may cause problems at these low voltages.

    Edit You could also try a voltage doubler.
     
  8. Juzzac

    Juzzac

    6
    0
    Mar 1, 2015
    Thanks Duke,
    A voltage doubler might be the best idea, can you please point me in the direction of exactly what i will need?

    Thanks again for your time
     
  9. KTW

    KTW

    273
    15
    Feb 22, 2015
    Juzzac; Did you measure the voltage at the connector?
     
  10. BobK

    BobK

    7,682
    1,685
    Jan 5, 2010
    I would use a rectifier to supply a signal to a transistor to switch a 3VDC supply to the buzzer.

    Bob
     
    duke37 likes this.
  11. duke37

    duke37

    5,360
    765
    Jan 9, 2011
    A voltage doubler is two diodes in series (1N400*) driven at the junction with a capacitor. 10μF should be enough at this frequency and an output capacitor of, say 100μF.
    If you go for the transistor solution, you could use 12V and wake the neighbours !
     
  12. Juzzac

    Juzzac

    6
    0
    Mar 1, 2015
    Thanks Duke37,
    I am back on the project, so can i use two 1n4004 diodes and 10 uf electrolytic capacitor as C1 and 100uf as C2 as per the attached diagram ?
    Thanks again for your help
     

    Attached Files:

  13. duke37

    duke37

    5,360
    765
    Jan 9, 2011
    That would work and is the circuit used for high voltages where the voltage is split between C1 and C2. In your case, replace C1 and C2 by a single 100μF capacitor and drive the junction of the diode with a 10μF capacitor. This could be changed to a smaller foil capacitor if the frequency is high enough.

    Schottky diodes will drop less voltage but use what you have. I bought a pocket full of 1N4007 since they will stand high voltages on other projects.
     
  14. Juzzac

    Juzzac

    6
    0
    Mar 1, 2015
    Thanks Duke, I have tried that circuit on the bench using a 9VAC power and a higher voltage rated buzzer and it works, it doubles the voltage and converts to DC however it doesn't seem to function very well when i pulse the input simulating the parking sensors beeping faster as you get closer to a object, (when i disconnect the power supply it gets quieter slowly, not on/off). I then thought i would test it in the car with the low tone buzzers i have and it didn't work at all, the output voltage was DC 0.5v. I think it must be to much load on the sensor module.
    Do you think that bob's suggestion of using a rectifier to power a transistor might be worth a try ?
    Can you point me in the direction of a circuit I would use ? From what i gather i would have to use a external 5v power supply from the car.

    Thanks again for all your help with this

    Juzza
     
  15. duke37

    duke37

    5,360
    765
    Jan 9, 2011
    If the sound takes too long to die away, then the 100μF capacitor is too large.

    If you are happy to use a separate power supply, then the transistor switch as suggested by Bob is the way to go. You could use 5V but why not use 12V without extra circuitry? Get a siren to suit.

    Measure the voltage output of the doubler with no load.
    Calculate the size of the resistance needed to drive the base of a transistor.
    The transistor will need to be man enough to drive the sounder you chose and may need a diode across the sounder to eliminate high voltage spikes.
     
  16. Martaine2005

    Martaine2005

    2,716
    734
    May 12, 2015
    Hi, I am probably going to get shot down here but......
    Can your friend hear the cars horn/hooter ?
    I don't mean at close range like he presses the button and hears his...
    I have a friend who is totally deaf. I remember drawing a picture of a plane hitting the towers for him..
    I once followed him driving to a job in Brixton (London) and could not believe what I was seeing.
    Cyclists shouting at him, an ambulance with siren and me beeping him to pull over..
    I don't think he should ever have been given a driving license.

    I apoligise if this has offended anybody, but the truth in my own personal experience.
    Martin
     
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