Carriage Home Position Detection; Sequence Used For Pw Detection - Epson Stylus Photo R1800 Service Manual

EPSON Stylus Photo R1800/R2400

2.2.1.2 Carriage Home Position Detection

As in the conventional 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 as 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 1158/1500 counts or more in the PWM output under
CR Motor load positioning control.
P1 (number of output pulses from when power is switched on until 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 575/1500 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 1158/1500 counts or more in the PWM
output under CR Motor load positioning control, the printer judges that the
Carriage moved to the far right position (is 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.
The IC14 (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 the IC14 (ASIC), the IC5 (Motor Driver)
outputs the CR Motor drive current to the CR Motor.
Operating Principles

2.2.1.3 Sequence Used for PW Detection

The PW (paper width detection) Sensor installed on the Carriage Unit bottom is
used to control the printer according to various sequences.
The following briefly describes the PW Sensor operating principle.
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
Threshold value
The following sequences are performed.
Detection of Left and Right Edges of Paper and Control
Before Printing
The printer detects that paper has been loaded. And it 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. And 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 and Control
Before starting a print job, the printer detects the top edge of a loaded
single sheet of paper, roll paper, or board 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 and Control
After starting a borderless printing, the printer sets the off-range bottom
margin.
Detection of Edges of CD-R and Control
Before starting to print, the PW Sensor detects top, bottom, left and right
edges of the CD-R.
page 24.
Printer Mechanism
detection voltage: Paper present
detection voltage: Paper absent
See Section 2.2.3.4 CD-R Printing Mechanism on
Revision B
18