Display; Speed, Imbalance And Rotor Detection; Lid Lock System - VWR Mega Star 600R Service Manual

Display

The LCD is attached to the front panel. The connection to the main board is done by a RJ45 cable.
Data transfer as well the low voltage supply of 5VDC is verified. The LED backlight is supplied with
24VDC. The operating keys are managed by an own connection.

Speed, imbalance and rotor detection

The motor cover contains the detection circuits for speed, rotor and imbalance. The LED V37 on the
main board indicates the function of the speed and rotor detection. A measurement of the signal is
not possible.
Rotor detection
4 magnets mounted on each rotors bottom are detected by a
Hall Effect sensor in the motor cover. The magnets are
alternately arranged in polarity on a ring around the rotors
centre. The gap between 2 magnets varies with different rotor
types, but is at least 20°.
The magnets are switching a flip-flop stage by which different
pulse lengths and pulse intermissions are generated during one
rotor rotation. By this signal the CPU is able to detect up to 65
different rotors and the correct direction of rotation, too.
After the rotor has been recognized this signal is used for the
redundant speed measurement.
Speed detection
A Hall Effect sensor in the rotor cover counts the passing by
magnets. As the 4 magnets are arranged alternating in polarity,
2 north and 2 south poles make one revolution.
For safety reasons the speed detection circuit is redundant and
the rotor detection circuit is used to detect the speed, too, after
the rotor has been recognized.
Imbalance detection
After the rotor has been recognized, the depending vibration
curve is loaded from the NV-RAM. If vibration, which is detected
by an accelerometer in the motor cover, exceeds this curve, an
imbalance alarm is triggered by the CPU.

Lid lock system

The lid is closed by pressing the hook into the latch. Two micro switches monitor the correct position
of the hook and the emergency opening during the run. An alarm is triggered if one of these two micro
switches opens, while the rotor is spinning.
The latch is unlocked by a bi-directional stepper motor controlled by a stepper motor driver on the
main board. A micro switch is used for the 0-position finding after each opening and at power on.
For additional safety the motor driver is de-activated by a relay when the speed is above 120rpm.
FUNCTIONAL DESCRIPTION
4
2
0
0 2000 4000
rpm
3-5
6000