Assistant Service Manual
OPTIKON 2000
Code 121008S
6-5 Rev. D
6.2 CONTROL BOARD 393200
The 393200 Control board schematics have been logically divided in five
sheets:
1. Sheet 1/5 and 2/5 contain the logic part of the board:
- The main microprocessor 18F6520 with its reset circuitry. The
18F6520 is a powerful single chip processor produced by Microchip. It
includes EEPROM for the control software and for the calibration data,
CMOS static RAM, a TTL RS232 high speed serial interface (used to
interface to the GUI), internal timers and oscillators to generate PWM
analog outputs, 8 analog inputs and over 40 digital I/O lines. This
powerful LSI microprocessor integrates in one chip what would require
a full board of standard electronics.
- The I.V. pole interface: signals enter J3 connector of Control board.
Bottle UP control is connected to RC1 bit, whereas DOWN is
connected to RC2 bit. A potentiometer connected to the pole motor
reads the pole position. Potentiometer is powered by Varef., equal to
approx. 4.1 V. The potentiometer cursor is read by microprocessor at
AN1 analog input.
- An internal timer of the microprocessor is used to generate the variable
frequency sound associated with the vacuum level.
2. Sheet 3/5 contains a series of optocouplers designed to electrically
separate the signal circuitry of the microprocessor from the power
Darlington transistors that drive the various valves of the ASSISTANT.
3.
Sheet 4/5 contains:
- The electronic driver of the peristaltic pump. The pump is driven by a
12Vdc motor connected to J12. Q12 (TIP 122) delivers current to the
motor for pump rotation while Q11 (IRF520) short circuits the motor for an
immediate pump stop. Speed control is implemented by U18A: the resistor
R64 in series to the motor and resistor R52 for positive feedback at non-
inverting input of U18A act in order that if motor current consumption
increases, the motor driving voltage increases as well (motor torque
control). The microprocessor sets the pump speed by Pulse Width
Modulation: a square wave of variable duty cycle is output, the higher is
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