Description microscope M695

Service manual M695

09/93 3077-HWE

Doc code 636 718

 

 

 

Motorized focusing

The control signals (0V/5V) for A/B FOCUS UP and A/B FOCUS DOWN

 

pass through the swingarm cable and the Lamp Servo to reach Zoom Servo

 

at the microscope. ZOOM UP/DOWN activates the end-stage transistors in

 

the zoom servo board. The end-stage consists of a bridging circuit of transi-

 

stors, and so the motor can drive the focusing mechanism in both senses of

 

rotation.

Recognizing end of range

Presetting the focus displacment speedTravelling to the mid-position

Reflexive light barriers sense 2 encoder tracks at the circumference of the focus gear: UP/DOWN+CENTER and LIMIT.

With the light barrier UP/DOWN, through gate 2 or 5, the direction of the arrived limit position is decoded. Through gate 2 or 5 LIMIT blocks FOCUS UP or DOWN at the following NAND-gate. The final stage is then blocked for that direction.

The displacement speed is altered with the supply voltage for the focus motors. The final stage only has a switching function. The FOCUS SPEED level is the reference for the voltage regulator on the focus servo board.

The current through the final stage is limited to about 140mA.

Triggered by:

•Pressing key “Center Position” at the focusing unit

•Switching on the microscope.

•30ms-pulse to FOCUS SPEED from control unit. The comparator recog- nizes when FOCUS SPEED is at GND potential.

The following functions are activated as a result:

1.The selflock circuit is triggered. Gate 2 and 5 block FOCUS UP and DOWN to the final stage. The voltage supply for the focusing motor is switched to maximal speed.

2.Lightbarrier UP/DOWN+CENTER senses, at which side from mid-posi- tion the focus gear is staying. Through gate 3 or 4 the final stage is controlled - the motor drives the focus gear toward mid-position...

3. ...until the light barrier on the sensor board detects the crossing from dark to bright at mid-position. The selflock cicuit is reset (Clr) - the motor stops.

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