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9

The CPU inputs each analog voltage and changes the internal data of the program using the AD converted data.

This circuit is used for testing. When the connection indicated by the dotted line in the above diagram is shorted, the
unit is put in time compression mode.

There are two thermistors TH1 and TH2 in the temperature sensor circuit. They are connected in serial with resistors
R14 and R15, and the divided voltage is applied to CPU IC1 analog input pins 62 and 63. CPU IC1 performs AD
conversion on the analog voltages from these two thermistors and performs the most appropriate control.

R31 R33

R35 R37 R39

R30

5V

R32

R34 R36

JP25

R38

CPU (IC1)

Internal fan speed adjustment

Heat exchanger compensation

Outdoor heater rating frequency

Outdoor cooler rating frequency

5V

R13

CPU (IC1) pin 61

+

C11

5V

R15

R14

TH1

TH2

–

+

C12

–

CPU (IC1) pin 63

CPU (IC1) pin 62

10

HIGH (5V) is input to the CPU when switch SW1 is pressed. The CPU begins automatic operation when this is
detected.

The varistor protects the control circuit from a large power surge such as lightning. When the surge is large, the varistor
is shorted and the fuse blows. The varistor will also be broken. When this happens there will be a large crackling nose.
Replace the fuse and varistor.

NR1

FU1

AC 220/240V

R12

5V

SW1

CPU (IC1) pin 37

11

The indoor fan circuit is composed of a drive circuit and a rotation frequency detection circuit.

As shown in the diagram below, phase control is used to control the indoor fan rotation. For each rotation of the motor,
three pulses are input from the rotation frequency detection circuit. The CPU reads these pulses, and computes the fan
rotation frequency, then adjusts the SSR ON timing to attain the target frequency.
IC2 is a transistor array that drive SSR.

AC 220/240V

12V

5V

12V

C1

C21

CNR1

NF1

CPU (IC1) 
pin21

CPU (IC1) pin 49

FAN

MOTOR

SSR1

R1

IC2

R22

R21

R20

C16

SSR ON

CPU (IC1)

 pin 49

AC Power

Supply

Fan motor

InPut

Clock

When CPU IC1 pin 49 is asserted to HIGH, SSR goes ON until the next zero crossing point. The clock is used for the
CPU output timing.

12

This is a circuit to drive the stepping motor for operating the louver. The drive pulse is shown in the diagram below.

IC2 is a transistor array that sends the current flowing to the motor coil.

12V

12V

IC2

CPU (IC1) pin 50

CPU (IC1) pin 51

CPU (IC1) pin 52

CPU (IC1) pin 53

LOUVER MOTOR

Power supply 

clock

CPU (IC1)

 pin 50

CPU (IC1)

 pin 51

CPU (IC1)

 pin 52

CPU (IC1)

 pin 53