Display Board
Principles of Operation
Force EZ-C Series Service Manual
5-13
RF Indicator Lamps
The RF indicator lamps illuminate during RF activation to indicate the presence
of RF power. Four incandescent bulbs (LP1–LP12) illuminate each of the three
indicator bars (bipolar, cut, and coag) on the front panel:
•
LP1–LP4 illuminate the bipolar bar, changing its color from white to blue to
indicate bipolar activation.
•
LP5–LP8 illuminate the yellow bar, indicating cut activation.
•
LP9–LP12 illuminate the blue bar, indicating coag activation.
Field effect transistors (FETs) Q1, Q4, and Q5 turn the RF indicator lamps on and
off. Resistors R2, R3, R4, R10, R39, R40, R42, R44, R49, R50, R52, and R54 set
the amount of current flowing through the lamps when they are turned on. The
value of these resistors varies for each indicator bar, depending on the color of the
bar, to make the different colors of the bars illuminate with equal intensities. Pull-
down resistors R1, R47, and R48 attach to gates Q1, Q4, and Q5 to reduce the
input impedance of Q1, Q4, and Q5 as seen by the main microcontroller on the
Control board. This rounds off the edges of these digital signals, reducing high
frequency emissions. The lowered impedance also reduces the susceptibility of
the circuit to noise from other circuits.
LED and Seven-Segment Display Drivers
This circuit contains two display drivers: the LEDs and the seven-segment
displays The LEDs indicate modes of operation, REM condition, and the selected
footswitch mode. The seven-segment displays indicate bipolar, cut, and coag
power settings.
Each display driver (U5 and U6) can drive up to eight banks of eight LEDs by
multiplexing the time that it turns each bank on. Wiring the banks together
increases the time that a group of LEDs can remain on, effectively increasing the
brightness of that group.
U6 drives the discrete LEDs. These include green indicators for several displays:
•
cut modes (pure and blend)
•
coag modes (low and high)
•
bipolar and accessory footswitch arrow indicators
•
eight red/green bicolor LEDs for the REM indicator
The anode of the mode and footswitch selection LEDs (D1–D6) connect to driver
U6, pin 16 (digit 2) and pin 23 (digit 3). Using pairs of the driver digit lines makes
the effective duty ratio for these LEDs 1/4:
•
The red anodes of the REM LEDs connect to U6, pins 17 and 20 (digits 4 and
5) for a 1/4 duty cycle.
•
The green anodes of the REM LEDs connect to U6, pins 18, 21, and 22 (digits
6-8) for a 3/8 duty cycle.
Содержание Force EZ - C Series
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