Prev: John Larkin = Criminal LIAR
Next: Ed Hardy women jeans cheap wholesaler (paypal payment)
From: John Fields on 7 Apr 2010 15:22
On Wed, 07 Apr 2010 13:35:49 -0400, Spehro Pefhany
<speffSNIP(a)interlogDOTyou.knowwhat> wrote:

>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 ?

---
Good one! :-)

That'll work well if the bounce lasts for <= about 40ms:

Version 4
SHEET 1 1168 680
WIRE 112 -240 -80 -240
WIRE 384 -240 112 -240
WIRE 704 -240 384 -240
WIRE 1024 -240 704 -240
WIRE 1088 -240 1024 -240
WIRE 112 -208 112 -240
WIRE 384 -192 384 -240
WIRE 1088 -192 1088 -240
WIRE 752 -128 512 -128
WIRE 1024 -128 1024 -240
WIRE 1024 -128 976 -128
WIRE 112 -64 112 -128
WIRE 208 -64 112 -64
WIRE 384 -64 384 -112
WIRE 384 -64 272 -64
WIRE 752 -64 384 -64
WIRE 1088 -64 1088 -112
WIRE 1088 -64 976 -64
WIRE 752 0 592 0
WIRE 1088 0 1088 -64
WIRE 1088 0 976 0
WIRE 432 32 256 32
WIRE 112 64 112 -64
WIRE 592 64 592 0
WIRE 704 64 704 -240
WIRE 752 64 704 64
WIRE 192 80 160 80
WIRE 304 96 256 96
WIRE 1088 96 1088 0
WIRE -80 112 -80 -240
WIRE 304 128 304 96
WIRE 432 128 432 32
WIRE -80 256 -80 192
WIRE 112 256 112 144
WIRE 112 256 -80 256
WIRE 160 256 160 128
WIRE 160 256 112 256
WIRE 304 256 304 208
WIRE 304 256 160 256
WIRE 432 256 432 208
WIRE 432 256 304 256
WIRE 512 256 512 -128
WIRE 512 256 432 256
WIRE 592 256 592 144
WIRE 592 256 512 256
WIRE 1088 256 1088 160
WIRE 1088 256 592 256
WIRE -80 336 -80 256
FLAG -80 336 0
SYMBOL Misc\\NE555 864 -32 R0
SYMATTR InstName U1
SYMBOL voltage -80 96 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value 12
SYMBOL sw 112 160 R180
WINDOW 0 43 40 Left 0
WINDOW 3 40 76 Left 0
SYMATTR InstName S1
SYMBOL res 128 -112 R180
WINDOW 0 36 76 Left 0
WINDOW 3 36 40 Left 0
SYMATTR InstName R1
SYMATTR Value 270k
SYMBOL cap 272 -80 R90
WINDOW 0 -50 34 VBottom 0
WINDOW 3 -42 33 VTop 0
SYMATTR InstName C1
SYMATTR Value 1e-7
SYMBOL res 368 -208 R0
SYMATTR InstName R2
SYMATTR Value 10k
SYMBOL res 576 48 R0
SYMATTR InstName R3
SYMATTR Value 1000
SYMBOL res 1072 -208 R0
SYMATTR InstName R4
SYMATTR Value 910k
SYMBOL cap 1072 96 R0
SYMATTR InstName C2
SYMATTR Value 1e-6
SYMBOL voltage 304 112 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 24 104 Invisible 0
SYMATTR InstName V1
SYMATTR Value PULSE(0 1 1 1e-6 1e-6 1.5 2 1)
SYMBOL Digital\\or 224 128 R180
SYMATTR InstName A1
SYMBOL voltage 432 112 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 24 104 Invisible 0
SYMATTR InstName V3
SYMATTR Value PULSE(0 1 2.5 1e-6 1e-6 1e-5 20e-3 10)
TEXT -72 280 Left 0 !.model SW SW(Ron=1 Roff=10Meg Vt=0.5Vh=0)
TEXT -72 312 Left 0 !.tran 5

1 megohm will take it up to about 140ms.

JF
First  |  Prev  | 
Pages: 1 2 3
Prev: John Larkin = Criminal LIAR
Next: Ed Hardy women jeans cheap wholesaler (paypal payment)