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