Beckman Couler ALLEGRA X-12/R, Service Manual, Page: 56 / 83

Section 4: Schematics
4.1 ALLEGRA X-12/R, X-15R CIRCUIT DESCRIPTION
Control Driver Board
General
The Control Driver Board (CDB) is a Motorola 68332 based board providing all
instrument control.
Power Supply
A single power supply generates 3 voltages; +24V (LD62), +5V (LD63), and +3.3V
(LD65). The +24V supply is not regulated, however the +5V U34 and +3.3V U35
supplies are regulated. The output of the+5V supply feeds the +3.3V regulator. A 2A
fuse is in series with the primary winding of the transformer for protection.
VREF is the 5 VDC reference. VREF is generated from +24VDC via ZR1,
LM4040 a precision voltage reference. This voltage is used for the A/D Converter U25,
the Imbalance Circuit, and the Motor Driver Board.
The Power Fail circuit sends a fault signal to the microprocessor if the supply falls below
20V DC.
Driver Board Control
Via J21
The microprocessor generates PWM signals that are fed to the Driver Board. Other
control and status signals such as Drive Enable, Brake and, Fault detection are interfaced
to the Driver Board through this connector.
A/D Circuit
The Analog to Digital Conversion is achieved by using a MCP 3208, 12 bit 8 channel SPI
Serial Interface, A/D Converter U25. The A/D converter is referenced to VREF and
converts the following signals: DC-Link, Current, Thermistor and Imbalance.
Thermistor
Via J7
Termistor is buffered through Op Amp U36A to the A/D Converter U25.
Tach Input
Via J10
The Tach signal is fed into the microprocessor via TPU6.
Door Interlock Circuit
The Door Interlock is controlled by LM2917 U106, a Frequency to Voltage Converter,
using the TACH Signal as its input.
Allegra X-12/R, X-15R Service Manual 7/04 4-1