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8.2 Sensor circuit
This circuit detects the temperature by dividing voltage
with resistance and sensor and bringing the voltage value
into CPU, using the characteristics of the sensor that
resistance varies with different temperatures. TA and TC
have the same circuit composition.
8.3 12V power source circuit
Full-wave rectification by diode bridge (DB01) of alternate
current supplied from power transformer followed by the
provision of transistor (Q01) gives DC12V power source
( H ).
When TA and TC are at 25
°
C approximately, the voltage level is some 2V both at points F and G .
If F / G are at GND or 5V, abnormal condition prevails such as opening or short-circuit of the sensor.
Built-in IC (TA8000S) is used to produce 5V power source
( J ). Also, it sends signals to reset port ( L ) of
microcomputer which is in stand-by at 0V and starts its
operation with the signal of 5V.
Watchdog timer output gives the signal from
microcomputer as illustrated below. This indicates that
the microcomputer is working in normal routine. For
example if the microcomputer is straying due to noise
and so on, this waveform is not produced. In case there
is no waveform, it plays the role of restoring normal
condition by inputting the resetting "0V" to the
microcomputer.
8.4 5V watchdog timer circuit
This circuit makes indoor microcomputer reset by way of
hardware when you keep on pressing the check key of
remote controller for longer than a predetermined period.
It plays the role of resetting microcomputer from the
remote controller when it strays. The point ( M ), which
is normally at the level of 5V, drops down to the GND
level in the rest operation.
8.5 Reset circuit
TC Sensor
To Microprocessor
Reset input
Watchdog output
K
L
Serial input from
remote controller
Watchdog
timer
output OV
WHI
TA Sensor
F
G
M
C
Heronhill - for all your Toshiba requirements
Tel: 01823 665660
www.heronhill.co.uk
Fax: 01823 665807
