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LC Oscillator
VAD (+5V)
r - - - - - - 1
c P U . . , ,
pPD78c11
ANO
Reference
Voltage
Generator
o
BREATH SENSOR BLOCK
Weak breath
- - ; , - .
I = lll9ll
;
v = l o w
@ Rectifier
:
A . " i -
, . ' . .
8),'Relerence Vottage
i Generator
@ comparator
VAD (+5V)
,1 Q5t
''le5
. . An oscillator which is composed of a coil and capacltors.
As the core in the coil moves by the breath, inductance of the coil varies by
the blowing strength.
Variation of the induclance changes the frequency and peak to peak voltage
of the oscillation signal.
Namety, when the breath is weak, osoillation trcque.hcy is high and peak to
peak voltage is low.
,,',i
On the contrary, strong blow lowers the frequenry dnd heighten the voitage.
Strong breath
f = l o w . . ,
v; nbfr,
Atterthe oscillation signalinto a DC voltage.*Strongerthe
breath, higherthe
output voltage.
. . . Compares the Rectifier and Rbftlience Voltage Generator outputs.
i
When thb instrument is not blown, the output vbltrage-olOlixparatorls,zAro
volt. The output voltage riscs in accordance with the breath strength.
, 4
" * t -
- ' 1 3 -
i i
ji"
ffr;
ff
ff
iiil:i
'ri'.,ji
I_ ,r-,.-
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