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S3F84B8_ALL-IN-ONE IH COOKER_AN_REV 0.00 2 HARDWARE IMPLEMENTATION
2-13
2.6 OTHER FUNCTIONS
2.6.1 PAN DETECTION
Pan-on detection is executed every 2sec when the system is idle. It is useful when you press the Start key first
and then put the pan on. In principle, even though the IGBT is turned on, there will not be any oscillation before
the pan is put on the panel. In S3F84B8, comparator 0’s output can be set as the clock source of Timer C. After
starting 1-cycle PWM output and waiting for about 3 oscillation cycles, if TCCNT>1, Pan status = on; else Pan
status = off. Pan-remove detection is executed every 1.5s when the system is working. It is useful when you
directly remove the pan from the panel without pressing the Stop key.
Pan-remove detection is done by current measurement, that is, when the sensed current is small, the system
considers the pan as removed and turns idle.
2.6.2 BUZZER AND FAN CONTROL
Figure 2-8
shows the circuit diagram for buzzer and fan control.
+
C24 104M/50V
BUZZER1
Q3
8050
1
2
CN3
FAN
+18V
R26
1K
BUZ/FAN
Figure 2-8 Buzzer and Fan Control
The fan cools down the system while heating. Buzzer indicates error and key actions.
In Figure 2-8
, buzzer and fan share the same I/O. Due to C24, the DC signal controls fans on and off, while
square wave with high frequency determines the buzzer’s beep.
Note that C24 cannot be too large; else it will deteriorate the power of MCU and make the integrated analog
modules work unstably.