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From: John Fields on 6 Apr 2010 09:19
On Mon, 5 Apr 2010 19:07:56 -0700 (PDT), mike3 <mike4ty4(a)yahoo.com>
wrote:

>Hi.
>
>How would one make a circuit that has a buzzer that, upon a trigger
>being tripped, produces a buzz lasting, say 1 second, then stops until
>reset? Even with the trigger continuously depressed, the buzz can't
>last more than 1 second.

---
Does the buzzer have an internal oscillator?

JF
From: mike3 on 6 Apr 2010 19:36
On Apr 6, 7:19 am, John Fields <jfie...(a)austininstruments.com> wrote:
> On Mon, 5 Apr 2010 19:07:56 -0700 (PDT), mike3 <mike4...(a)yahoo.com>
> wrote:
>
> >Hi.
>
> >How would one make a circuit that has a buzzer that, upon a trigger
> >being tripped, produces a buzz lasting, say 1 second, then stops until
> >reset? Even with the trigger continuously depressed, the buzz can't
> >last more than 1 second.
>
> ---
> Does the buzzer have an internal oscillator?
>

It's a piezo buzzer powered with DC current.
(If it uses DC, wouldn't that mean it has the internal oscillator?)
From: John Fields on 6 Apr 2010 22:08
On Tue, 6 Apr 2010 16:36:52 -0700 (PDT), mike3 <mike4ty4(a)yahoo.com>
wrote:

>On Apr 6, 7:19�am, John Fields <jfie...(a)austininstruments.com> wrote:
>> On Mon, 5 Apr 2010 19:07:56 -0700 (PDT), mike3 <mike4...(a)yahoo.com>
>> wrote:
>>
>> >Hi.
>>
>> >How would one make a circuit that has a buzzer that, upon a trigger
>> >being tripped, produces a buzz lasting, say 1 second, then stops until
>> >reset? Even with the trigger continuously depressed, the buzz can't
>> >last more than 1 second.
>>
>> ---
>> Does the buzzer have an internal oscillator?
>>
>
>It's a piezo buzzer powered with DC current.
>(If it uses DC, wouldn't that mean it has the internal oscillator?)

---
Yes, in which case you can use this circuit: (View in Courier)


Vcc>-+---------+-----+-------+--------+----+
|R1 |R2 |R3 8| |R4 |
[10k] [10k][910k] +---+---+ [100k] |
| C1 | Rt| 2|_ Vcc _|4 | |C3
+-[100nF]-+-----|--O|T R|O---+ [100nF]
| | 6| | |C4 |
| +---|TH 555| [100nF] |
| | 7|_ |3 | |
| O +--O|D OUT|O---|----|---+
| O S1 +| | GND | | | |
| [1�F] +---+---+ | |[PIEZO]
| Ct|C2 1| | | |
GND>-+---------------+-------+--------+----+---+

C3 should be connected directly across pins 1 and 8 of the package and
as close as possible to the package.

A 555 is a non-retriggerable monostable, so when S1 is made the output
will go high for:

T = 1.1 RtCt

regardless of what is done with S1 during that time.

If your piezo doesn't need much current you can drive it with a 7555 and
delete C3. Check the piezo specs and the 7555 specs to see if it'll
work.

JF
From: John Fields on 6 Apr 2010 22:20
On Tue, 06 Apr 2010 21:08:18 -0500, John Fields
<jfields(a)austininstruments.com> wrote:

>On Tue, 6 Apr 2010 16:36:52 -0700 (PDT), mike3 <mike4ty4(a)yahoo.com>
>wrote:
>
>>On Apr 6, 7:19�am, John Fields <jfie...(a)austininstruments.com> wrote:
>>> On Mon, 5 Apr 2010 19:07:56 -0700 (PDT), mike3 <mike4...(a)yahoo.com>
>>> wrote:
>>>
>>> >Hi.
>>>
>>> >How would one make a circuit that has a buzzer that, upon a trigger
>>> >being tripped, produces a buzz lasting, say 1 second, then stops until
>>> >reset? Even with the trigger continuously depressed, the buzz can't
>>> >last more than 1 second.
>>>
>>> ---
>>> Does the buzzer have an internal oscillator?
>>>
>>
>>It's a piezo buzzer powered with DC current.
>>(If it uses DC, wouldn't that mean it has the internal oscillator?)
>
>---
>Yes, in which case you can use this circuit: (View in Courier)
>
>
>Vcc>-+---------+-----+-------+--------+----+
> |R1 |R2 |R3 8| |R4 |
> [10k] [10k][910k] +---+---+ [100k] |
> | C1 | Rt| 2|_ Vcc _|4 | |C3
> +-[100nF]-+-----|--O|T R|O---+ [100nF]
> | | 6| | |C4 |
> | +---|TH 555| [100nF] |
> | | 7|_ |3 | |
> | O +--O|D OUT|O---|----|---+
> | O S1 +| | GND | | | |
> | [1�F] +---+---+ | |[PIEZO]
> | Ct|C2 1| | | |
>GND>-+---------------+-------+--------+----+---+
>
>C3 should be connected directly across pins 1 and 8 of the package and
>as close as possible to the package.
>
>A 555 is a non-retriggerable monostable, so when S1 is made the output
>will go high for:
>
> T = 1.1 RtCt
>
>regardless of what is done with S1 during that time.
>
>If your piezo doesn't need much current you can drive it with a 7555 and
>delete C3. Check the piezo specs and the 7555 specs to see if it'll
>work.

---
A caveat...

If S1 is made and held down for longer than it takes the 555 to time out
and if there's any switch break bounce in S1, the 555 will be triggered
again and generate another 1 second pulse when S1 is released.

If that's the case, the switch will need to be debounced.

Will you need a circuit for that?

JF
From: Spehro Pefhany on 7 Apr 2010 13:35
On Tue, 06 Apr 2010 21:20:05 -0500, John Fields
<jfields(a)austininstruments.com> wrote:

>On Tue, 06 Apr 2010 21:08:18 -0500, John Fields
><jfields(a)austininstruments.com> wrote:
>
>>On Tue, 6 Apr 2010 16:36:52 -0700 (PDT), mike3 <mike4ty4(a)yahoo.com>
>>wrote:
>>
>>>On Apr 6, 7:19�am, John Fields <jfie...(a)austininstruments.com> wrote:
>>>> On Mon, 5 Apr 2010 19:07:56 -0700 (PDT), mike3 <mike4...(a)yahoo.com>
>>>> wrote:
>>>>
>>>> >Hi.
>>>>
>>>> >How would one make a circuit that has a buzzer that, upon a trigger
>>>> >being tripped, produces a buzz lasting, say 1 second, then stops until
>>>> >reset? Even with the trigger continuously depressed, the buzz can't
>>>> >last more than 1 second.
>>>>
>>>> ---
>>>> Does the buzzer have an internal oscillator?
>>>>
>>>
>>>It's a piezo buzzer powered with DC current.
>>>(If it uses DC, wouldn't that mean it has the internal oscillator?)
>>
>>---
>>Yes, in which case you can use this circuit: (View in Courier)
>>
>>
>>Vcc>-+---------+-----+-------+--------+----+
>> |R1 |R2 |R3 8| |R4 |
>> [10k] [10k][910k] +---+---+ [100k] |
>> | C1 | Rt| 2|_ Vcc _|4 | |C3
>> +-[100nF]-+-----|--O|T R|O---+ [100nF]
>> | | 6| | |C4 |
>> | +---|TH 555| [100nF] |
>> | | 7|_ |3 | |
>> | O +--O|D OUT|O---|----|---+
>> | O S1 +| | GND | | | |
>> | [1�F] +---+---+ | |[PIEZO]
>> | Ct|C2 1| | | |
>>GND>-+---------------+-------+--------+----+---+
>>
>>C3 should be connected directly across pins 1 and 8 of the package and
>>as close as possible to the package.
>>
>>A 555 is a non-retriggerable monostable, so when S1 is made the output
>>will go high for:
>>
>> T = 1.1 RtCt
>>
>>regardless of what is done with S1 during that time.
>>
>>If your piezo doesn't need much current you can drive it with a 7555 and
>>delete C3. Check the piezo specs and the 7555 specs to see if it'll
>>work.
>
>---
>A caveat...
>
>If S1 is made and held down for longer than it takes the 555 to time out
>and if there's any switch break bounce in S1, the 555 will be triggered
>again and generate another 1 second pulse when S1 is released.
>
>If that's the case, the switch will need to be debounced.
>
>Will you need a circuit for that?
>
>JF

Just increase R1 to 270K ?

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