Smiths Graseby MS16A, Техническое и сервисное руководство

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Te c h n i c a l S e r v i c e M a n u a l I s s u e 6 ( February 2 0 0 5 ) 3 — 3
S m i t h s M e d i c a l
3
M S 1 6 A S y r i n g e D r i ve r
Chapter 3 - Circuit Descriptions
Refer to Figures 3-1, MS16A Circuit diagram and 3-2, MS16A Printed
circuit board layout .
Logic
The Custom Integrated Circuit IC1 contains a very low power
oscillator, which operates at a fixed frequency. The output of the
master-clock is fed into a divider chain, which includes binary-coded
switches SW4 and SW5, so that rates over a 99:1 range can be
selected.
IC1 also contains the switching electronics which control the Start,
Motor Drive and Guard circuits.
Start
The battery return line (0V) is switched by transistor TR3, which is
controlled from pin 11 of IC1. This control is reset by a negative-going
pulse at IC1, pin 10. Since IC1, pin 10 is biased low through resistor
R2, the negative-going pulse is provided in the transition period
during operation or release of the
START/TEST
button (SW1).
Diode D1 (a low voltage-drop type) protects the circuit components
from damage if the battery polarity is reversed.
Motor drive
In the operation mode, IC1, pin 21 produces a square-wave pulse
train, the frequency of which is determined by the setting of the Set
Rate rotary switches SW4 and SW5. When the output from IC1, pin
21 goes high, transistor TR2 is turned on and TR1 is turned off.
With the cam-operated switch (SW3) in the position shown in Figure
3.1 , the motor circuit is completed via TR2, and the motor runs until
the cam operates the switch S3, (1/6 revolution). Because TR1 is
turned off whilst TR2 is conducting, the motor circuit is broken and
the motor stops (perhaps after some overrun). When the output from
IC1, pin 21 goes low, transistor TR2 is turned off and TR1 is turned
on.
The motor circuit is now completed via TR1 and the motor runs until
the cam-operated switch (SW3) returns to its original position
(another 1/6 revolution). Because TR2 is turned off whilst IC1/21
remains low, the motor circuit is once again broken until the next
high output from IC1, pin 21 restarts the sequence.
Since each motor pulse results in 1/6 of a revolution of the leadscrew,
the actuator advances the syringe plunger by 1/6 of the thread pitch,
that is by 0.117 mm.
SM0105-3-6.PMD 2/23/2005, 2:56 PM 3