Theory of Operation 7
1100 Series WS MWS Reference Manual 221
Sampling Unit Control
Needle lock, metering device valve and peristaltic pump motors are driven by
controlled pulse-width modulation in the same way as the ST L6506 (see
“Transport Unit Control" on page 220). The motors require fast speed but do
not require precise position control. Therefore, a closed loop servo system is
not required. Commutation is done in FPGA logic. The needle lock, metering
device and valve motors use ST L6203 output drivers to deliver the higher
currents required for fast movement or high torque. The peristaltic pump
drive is built with a ST L6201 circuit.
The movement sensing of the valve motor is done by two microswitches. Two
reflection light sensors are used to detect the end positions of the needle lock
device. One photo sensor is required to detect the home position of the
metering device. All the sensors are mounted on one flex board. The flex
board and motors are connected to the sampling unit distribution board
(SUD). The SUD board is connected to the Microtiter Plate Board (MTP) via a
flat-band cable (64 pin).
Figure 38 Sampling unit control
FPGA
Sensor Circuits
Needle Lock
Drive
Valve Drive
4.5A/Phase
Peristaltic
Pump
Drive 0.15
Metering
Drive
2A/Phase
Needle Lock
End-Position
Sensors (2)
Metering
Home-Positio
n Sensor
Sampling Unit
Distribution Board
Valve
End-Position
Sensors (2)
Microtiter
Plate Board
(MTP)
Via
sampling
unit flex
board
Safety Hall
Sensors (2)
Side Door
Safety Hall
Sensors (2)
Front Door
SLS Board
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