Loud Piezo Buzzer for Timer
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Posted by RobZ on November 15, 2006, 6:28 am
Please log in for more thread options Hi all, as the result of a dare, I am trying to build a shooting Timer. ( a timer that responds to the sound of a firearm being fired and records the times thereof). The timing is done by an ATMEL micro. the Start signal (from the Atmel) is a .5sec pulse. I have been using this to switch on a transitor to connect the 9V battery directy to the Piezo buzzer. this works fine except the volume/db of the buzzer is far to low. the Buzzer is rated 85Db with a supply voltage of 24V, another problem is that a buzzer of less than .25 Sec is too quick can any one assist in pointing me in the right direction re the following: a) Will a voltage doubler circuit (diode/capacitor network) work in this instance? b) must this "increased voltage" be stored in a capacitor before being able to be used ? c) if so, how do i connect it up to "release" the stored voltage - similiar to flash trigger , connecting to ground? d) given a 9v supply and a 5v trigger, could someone supply me a rough schematic ? e) the circuits i have been looking at (via google) typically use a 555 as an oscilator but they produce 200-300Volts! am i on the right track here? any Response is appreciated | ||||||||||||||||
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Posted by Chris on November 15, 2006, 9:16 am
Please log in for more thread options RobZ wrote: Hi, Rob. One at a time: a) Using a 555 as a voltage doubler will pump your 9V battery supply up to 18V, It should definitely work to increase your piezo beeper volume. b) Any voltage doubler uses an output cap to store the energy. The bigger the output cap, the more energy is stored. Your piezo isn't a high current load (probably less than 20mA DC), though, so an enormous storage cap shouldn't be much of a consideration. c-e) The basic 555 voltage doubler circuit is at this link: http://www.reconnsworld.com/power_voltdoubler.html It should work exactly as shown in the link (555 driving 1N4002s and 220uF caps). Your hookup diagram should look soomething like this (view in fixed font or M$ Notepad): | | BZ1 | |.-.| +18V | || || | | .-|| ||---' | | || || | | |'-'| | | | From ___ |/ | uC >-|___|-o-| 2N3904
| .-. |
| 2.2K | |> | 2.2K| | | | | | === | '-' GND | | | === | GND (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) With the higher voltage and full voltage turn on, your beeper should start up right away -- .25 seconds is plenty long for the beeper's internal oscillator to start up and give you a good tone. I hope this has been of use. Feel free to post again with more questions. Good luck Chris | ||||||||||||||||
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Posted by John Popelish on November 15, 2006, 10:04 am
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Chris wrote: > Hi, Rob. One at a time:
> > a) Using a 555 as a voltage doubler will pump your 9V battery supply > up to 18V, It should definitely work to increase your piezo beeper > volume. > > b) Any voltage doubler uses an output cap to store the energy. The > bigger the output cap, the more energy is stored. Your piezo isn't a > high current load (probably less than 20mA DC), though, so an enormous > storage cap shouldn't be much of a consideration. > > c-e) The basic 555 voltage doubler circuit is at this link: > > http://www.reconnsworld.com/power_voltdoubler.html > > It should work exactly as shown in the link (555 driving 1N4002s and > 220uF caps). Your hookup diagram should look soomething like this > (view in fixed font or M$ Notepad): > > | > | BZ1 > | |.-.| +18V > | || || | > | .-|| ||---' > | | || || > | | |'-'| > | | > | From ___ |/ > | uC >-|___|-o-| 2N3904 > | 2.2K | |> > | .-. | > | 2.2K| | | > | | | === > | '-' GND > | | > | === > | GND > (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) > > With the higher voltage and full voltage turn on, your beeper should > start up right away -- .25 seconds is plenty long for the beeper's > internal oscillator to start up and give you a good tone. > > I hope this has been of use. Feel free to post again with more > questions. This concept has a problem. The piezo buzzer is essentially a capacitor that looses energy into mechanical distortion when its state of charge changes. Replace it with a capacitor, in the above circuit, and it becomes pretty clear that there is no path for current (after the first pulse) through the transistor's collector. This circuit will produce a single tick when activated. It is not even a good idea to apply pulsating DC to a piezo. They last longest with AC, only. | ||||||||||||||||
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Posted by RobZ on November 22, 2006, 7:13 am
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Thanks Chris, Will give it a go! ps. sorry about the delay, somehow google did not inform me of a reply to topic? | ||||||||||||||||
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> as the result of a dare, I am trying to build a shooting Timer. ( a
> timer that responds to the sound of a firearm being fired and records
> the times thereof).
>
> The timing is done by an ATMEL micro.
> the Start signal (from the Atmel) is a .5sec pulse.
> I have been using this to switch on a transitor to connect the 9V
> battery directy to the Piezo buzzer.
> this works fine except the volume/db of the buzzer is far to low. the
> Buzzer is rated 85Db with a supply voltage of 24V,
> another problem is that a buzzer of less than .25 Sec is too quick
> can any one assist in pointing me in the right direction re the
> following:
> a) Will a voltage doubler circuit (diode/capacitor network) work in
> this instance?
> b) must this "increased voltage" be stored in a capacitor before being
> able to be used ?
> c) if so, how do i connect it up to "release" the stored voltage -
> similiar to flash trigger , connecting to ground?
> d) given a 9v supply and a 5v trigger, could someone supply me a rough
> schematic ?
> e) the circuits i have been looking at (via google) typically use a 555
> as an oscilator but they produce 200-300Volts!
> am i on the right track here?
> any Response is appreciated