D-Series Syringe Pumps - Isco

D Series Syringe Pumps
Section 4 Theory of Operation
The direction signals are output through port 1 of the microprocessor
(P1.0 for pump A). The pump A PWM signal is output on
pin 39 of the microprocessor. The PWM signals for pumps B and
C are generated by sections of an 82C54 counter (U113 for pump
B and U114 for pump C). The pump control signals are inverted
by a 74AC04 which drives the optical isolator LEDs located in
the pump module (see section 4.3, Pump Power Supply and
Motor Drive Power Amplifier).
Sections of the 82C54 also determine the rate of motor
movement. The rate signals return to the microprocessor on pins
24 (pump A), 25 (pump B), and 26 (pump C). If the motor control
appears to be functioning properly (holds position) but the motor
will not turn, the 82C540s (or their connection to the microprocessor)
should be checked.
The motor drive supply voltage is switched between two levels by
output pins 18, 19, and 20 of U128 for pumps A, B, and C, respectively.
Sections of a 2803 (U126) invert the signals and drive the
voltage switching relays. For more information, (See section 4.3)
Pump Power Supply and Motor Drive Power Amplifier.
Front Panel Standby Switch
Serial Port Interface
Accessory Interface
In addition to controlling the microprocessor reset function
described under Microprocessor Reset Circuit, one half of the
front panel ON/STANDBY DPDT switch is wired in series with
the motor enable signal. This signal controls the relay which connects
the motor to the motor drive power amplifier.
When the switch is set to the STANDBY position, the motor
drive is disabled and the electromechanical brake is applied. The
microprocessor can also disable the motor drives of all pumps by
turning off transistor Q102 (which is wired in series with the
standby switch). Q102 is turned off if a failure of the motor
control circuits is detected or if the pump pressure exceeds the
pump specification by 103.4 bar. Such failures are indicated on
the display by the messages FAILURE POSITION or FAILURE
PRESSURE. The front panel switch must be set to STANDBY
and then to ON to reset the system. If the condition was transient,
the pump may then operate correctly. If there is a permanent
failure, the message will repeat.
The hardware interface for the RS-232 serial interface consists of
line driver IC U107, a 14C88; and line receiver IC U110, a
14C89.
A non-serial digital and analog external interface is implemented
on the rear panel ACCESSORY connector. The terminals of this
connector are used for various purposes.
Analog Output The analog output option is described in Section 3.9.
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