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AR-651/810  SCANNING SECTION  6 - 5

The scanner motor is driven by the unipolar transistors as shown below. The current chopper method is

employed by the driver circuit to improve motor torque STK672-080 (IC4).

15

14

13

12

11

10

9

8

6

7

ENABLE

Mol

RESET

M3

CLOCK

CWB

M2

M1

Vcc2

Vref

A

A

B

B

BB

PG

SUB

5

4

3

2

1

Excitation

mode setting

Switching pulse

ON/OFF detection

Excitation

status monitor

CR oscillation

Phase

counter

Generation of

reference clock

PWM control

Generation of phase

excitation signal

Generation

of pseudo

sine wave

Switching

current

fraction ratio

AR-651/810  SCANNING SECTION  6 - 6

SCN-MOT

PWA-F-SLG

1

2

3

4

5

6

6

5

4

3

2

1

IC4

IC9

J8

SCNEN-0

SCNDIR-0

SCNRST

SCNREF-0A

SCNMD3-0

SCNMD2-0

SCNMD1-0

SCNCLK-0

1

2

3

4

J9

+36V

+36V

Scanner CPU

Motor

driver

The motor is rotated by setting the number of pulses.

* The internal circuit of the motor driver works at the rising and falling

edge of the pulse.

The direction of the motor rotation is determined by the setting level

of the signal

“H”…Clockwise direction (as seen from the output shaft)

“L”…Counterclockwise direction (as seen from the output shaft)

Note: When SCNMD3-0 is “L”, do not change the rotation direction

within 6.25µs before and after the rising and falling edge of

the pulse of SCNCLK-0.

“H” …Normal operation (The motor has been excited.)

“L”…Excitation drive output is forcibly shut OFF (the motor has not

been excited).

Motor wire current value is set in the range of 0 to 2.25 (A)/phase by

applying the analog voltage 0 to 5 (V).

Sets the excitation mode.

Note: Do not change the setting 

within

 5µs before and after the

rising  and falling edge of the pulse of SCNCLK-0.

Internal circuit of the driver is initialized by setting the motor to “L”

level (pulse interval: 10µs or more).

The motor drive circuit is automatically reset when the power is

turned ON.

SCNCLK-0

CLK input

Input

SCNDIR-0

Sets the direction

Input

of motor rotation

SCNEN-0

Cuts OFF the

Input

drive output

SCNREF-0A

Voltage to set value

Input

for the motor current

SCNMD1~3-0 Sets the 

excitation

Input

mode (1)–(3)

SCNRST

Reset

Input

Input signals

AR-651/810  SCANNING SECTION  6 - 7

Control circuit of the exposure lamp consists of the following 3 blocks.

(1) Lighting device for the Xenon lamp (Inverter)

Turns the exposure lamp ON/OFF.

(2) CCD sensor circuit

This circuit works to the convert the reflected light amount from the original surface and the shading

correction plate to the electrical signals. The reflected light amount from the shading correction plate is

read to control the exposure amount.

(3) Image processing circuit

The output signals from the CCD are digitized and the image processing such as gamma correction

and shading correction is applied to them.

PWA-CCD

PWA-CCD

Image processing
circuit

A/D

PWA-SLG

Main CPU

IC37

Original

Shading correction plate

Exposure lamp (Xenon lamp)

CCD sensor

Lighting device
for Xenon lamp

(Inverter)

Scanner

CPU

AR-651/810  SCANNING SECTION  6 - 8

External electrode type Xenon fluorescent lamp is used as an exposure lamp in this copier.

(1) Structure

The fluorescer is applied to the in-

side surface of the lamp pipe (ex-

cept for a part which serves as an

opening) which is filled with the Xe-

non gas.

A pair of the external electrodes

covered by film with adhesive agent

is attached around the pipe.

(2) Behavior inside the lamp

The electron inside the pipe is led

to the electric field by applying volt-

age to the pair of the external elec-

trodes, and the discharge is started.

The electrons then flow and clash

with the Xenon atoms inside the pipe

to excite them and allow them to

generate ultraviolet rays. This ultra-

violet rays convert the fluorescer into

visible light.

(1)Electrode (2)Electron (3)Xenon atom (4)Ultraviolet ray (5)Fluorescer
(6)Visible light (irradiated from the opening to outside the pipe)
(7)Opening (8)Harness

PET film

Aluminum tape
electrode

Adhesive agent

Glass valve

Fluorescer

Xenon gas

(1)

(6)

(8)

(7)

(5)

(2)

(4)

(3)