Filter Wheel Drive; Monochromator Grating Limit Switch; Serial Port; Parallel Port - Thermo Scientific GENESYS 20 Service Manual

Electrical Circuit Description and Adjustment

Filter Wheel Drive

The filter wheel stepper motor is driven by open-collector transistors in U37.
When moving the 12 volt unipolar stepper motor, Q2 is turned on to drive the
motor with 12 volts. Once the motor is at rest, Q2 is turned off and the motor is
held by 4.3 volts through D18 to reduce power consumption. The filter wheel
position is initialized by scanning for the odd-shaped orange filter position and
locating the edge of the aperture.

Monochromator Grating Limit Switch

A closure of the limit switch attached to J11 signals a coarse initialization of the
monochromator during instrument power-up.
Cooling Fan
A cooling fan is powered by +12V through J14.
Serial Port (RS232 or Serial Printer)
An RS232C format serial port is available at the DE-9 connector J3. U8
provides voltage level translation from +5 volts and ground to ± 12 volts. Direct
I/O control lines are used for all signals because of the timing critical nature of
the communications protocol. Two data lines (TXD/RXD) are used and two
control lines (RTS/CTS) are available for hardware handshaking if enabled by
the software. Baud rates are software selectable over the range of 300-19200
Baud. A serial printer can also be operated from this port. For further
information refer to the Operator's Manual.
Parallel Port (Centronics Printer Interface)
U6, U7, U9, U10, U11, and U13 provide the logic and latches to control either
an internal or external parallel Centronics printer. The active port is software
selectable by the user. Direct I/O lines are also necessary to control the printers.
The printer controls are accessed through the keyboard. The external parallel
printer attaches to the DB-25 connector J2.
Pump and Thermoelectric Flowcell Accessories
There is no support for these accessories at this time.
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