D-Series Syringe Pumps - Isco

D Series Syringe Pumps
Section 4 Theory of Operation
4.5 Automatic Pump Type
Indication
4.6 Optical Indicators
Piston Travel Limit
Sensors
Quadrature Motor Angular
Position Sensors
U108 automatically indicates to the microprocessor which pump
type is connected to a given port. In addition, when the pressure
transducer is connected, the signal labeled PC-1 (pump code 1) is
grounded at the pressure amplifier circuit board. This indicates
its presence to the controller. The pump will not operate without
the pressure transducer connected.
An optically coupled interruptible sensor is mounted at each
limit of piston travel. A mechanical flag blocks the light path of a
sensor when the piston is at the cylinder full or cylinder empty
position. The optotransistors are connected to pull the limit
signals high when the light path is open (transistor on). When
the light is blocked, resistors R125 or R126 pull the signal low.
Additional pull down resistors are located in parallel on the
control circuit board. With this connection, the most common
failures of the optodevice (such as a failed LED or a nonconducting
transistor) will stop the pump with an indication of cylinder
full or empty. The LEDs are wired in series so that an open
circuit of either will stop the pump.
The limit sensors also disable the motor drive through opto-couplers
U105 and U106 when a limit is reached. The circuit
remains enabled, to drive the piston away from the limit.
Motor position feedback to the microprocessor is generated by
two optically interrupted sensors which span a rotating etched
metal disk. This sensor is an enclosed sensor: HEDS-5500 II A06
(500 line) for the 1000D and 65D; HEDS-5500 II E06 (200 line)
for all other pump types. Two rows of slots in the disk are
arranged in quadrature (or 90 electrical degrees out of phase)
with respect to each other. When the motor is rotating in the
direction which moves the piston up, the TACHA signal leads the
TACHB signal. The order reverses in the opposite direction of
rotation. The light sensors are integrated circuits which use a
photodiode, followed by amplification circuitry which drives the
output high when light from the LED passes through the disk
slots, and low when the light is interrupted.
The +5-volt power supply for all optical sensors originates at the
pump, but is first passed to the controller and back to the pump
to insure that the sensors do not apply input signals to the controller
logic without the logic +5-volt supply present. This is necessary
because when multiple pump modules are connected to
the same controller; the B and C pumps (which do not power the
controller) may be connected to mains power without the A pump
powered. Therefore, all optical sensors in a multiple pump
system are powered from the pump A power supply.
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