Epson 1400 - Stylus Photo Color Inkjet Printer, Service Manual, Page: 24 / 168

EPSON Stylus Photo 1390/1400/1410 Revision B
OPERATING PRINCIPLES Printer Mechanism 24
2.2.1.2 Carriage Home Position Detection
As in the previous model, the Carriage Home Position is detected using the drive
current of the CR Motor and the speed/position signal of the CR Linear Encoder.
The basic home position detection sequence is described below.
1. The CR linear encoder pulse counter in the CPU is reset by the initialization
operation performed at power-on.
2. When the CR Motor rotates counterclockwise, the Carriage Unit moves from left
to right. When the following conditions are satisfied, the CPU assumes that the
Carriage Unit made contact with the right frame.
„ The ASIC detects 935/1500 counts or more in the PWM output under CR
Motor load positioning control.
„ P1 (number of output pulses from when the power is switched on till the
Carriage Unit makes contact with the right frame) is 19 steps or less.
3. When the CR Motor rotates clockwise, the Carriage Unit moves from right to left.
When the following conditions are satisfied, the CPU assumes that the Carriage
Unit reached the CR lock confirmation position.
„ The ASIC detects 600/1500 counts or more in the PWM output under CR
Motor load positioning control.
„ A difference between P1 and P2 (number of output pulses from when the
Carriage Unit made contact with the right frame until it reaches the Carriage
lock confirmation position) is 19 steps or less.
4. When the CR Motor rotates counterclockwise to move the Carriage from left to
right and the CPU detects 935/1500 counts or more in the PWM output under CR
Motor load positioning control, the printer judges that the Carriage has moved to
the far right position (in contact with the right frame).
5. When a difference between P1 and P3 (number of output pulses from when the
Carriage Unit reached the Carriage lock confirmation position until it makes
contact with the right frame) is 4 steps or less, the printer judges that the Carriage
Unit is in the home position.
IC9 (CPU-ASIC) sets the drive current value adequate for the Carriage Unit motion
and outputs it to the motor driver.
Based on the signal output from IC9 (CPU-ASIC), IC11 (Motor Driver) outputs the CR
Motor drive current to the CR Motor.
2.2.1.3 Sequence Used for PW Detection
The PW (paper width) Sensor installed on the bottom of the Carriage Unit is used to
control the printer according to various sequences.
The following briefly describes the operating principle of the PW Sensor.
A dark voltage is measured by the PW Sensor in three places at the right flat area (area
without the absorber) on the Front Paper Guide every time the printer is turned on, and
the measurement values are saved into the EEPROM as threshold values.
„ Threshold value detection voltage: Paper present
„ Threshold value detection voltage: Paper absent
The following sequences are performed.
† Detection of Left and Right Edges of Paper Control
„ Before Printing
The printer sets the print range according to the paper-size information from
the Driver and the actual paper-size detected by the PW sensor.
„ During Printing
When executing a borderless printing, the printer sets the off-range margins
by detecting the paper edges with the PW Sensor. When the resolution is 1440
x 1440 (VSD3) or 2880 x 1440 (VSD3) dpi, the printer performs the Off-
Range Thinning Out Control to make a further correction to the off-range
margins.
† Detection of Top Edge of Paper Control
Before starting a print job, the printer detects the top edge of a loaded single sheet
of paper to set the off-range top margin. (Only when not detecting the top edge of
paper with the PW Sensor.)
† Detection of Bottom Edge of Paper Control
After starting a borderless printing, the printer sets the off-range bottom margin.
† Detection of Edges of CD-R Control
(The Stylus Photo 1390 is not equipped with CD/DVD related units.)
Before starting to print, the PW Sensor detects top, bottom, left and right edges of
the CD-R.
See Section 2.2.3.3 CD-R Printing Mechanism on page 29.