Epson LQ-2550 Technical Manual page 119

2.3.4.11 Case Open Sensor Circuit
Figure 2-70 shows the case open sensor circuit. This circuit employs an IC including a hall-effect element
that can detect a magnetic field.
CPU
SUB
(7B)
NOTE: The output of the hall-effect IC goes LOW/HIGH when the IC moves close to/away from the
magnet.
Table 2-47 shows the relationship between the printer cover state and the voltage at the AN 1 terminal
of the Sub
CPU.
Closed
Open
R104
AN 1
T
A V
S S
Figure 2-70. Case Open Sensor Circuit
Table 2-47. Printer Cover State and AN1 Voltage
Printer Cover State
5 5 CN21
H a l l - E f f e c t
5
o
2-73
Upper Case
Magnet
Magnetic Field
REV.-A