Define_HW_limits

Define hardware limits in Pannoramic scanners

This chapter summarizes the knowledge and procedures to define hardware limits for stepper motor driven moveable parts in Pannoramic scanners in global and detailed aspects; used with the PCON, P250, SCAN, MIDI and DESK!

Contents

General

Movement ranges and limits

Sensor “Home1” and hardware limits

The file “MicroscopeConfiguration.ini”

Techniques to define hardware limits

Units and their hardware limits

Requirements

· Service program “SlideScannerService.exe”

· Diverse hex key bolt drivers (only for some units, where the bumper position can be adjusted)

General

The Pannoramic scanner includes hardware units with a stepper motor driven moveable part.

The moveable part, except it can move endless, needs a start point and an end point as well, so its movement is limited by the use of a hardware limiter and a bumper surface.

Because lost steps occur, if the bumper surface bumps against the limiter, the limit positions have to be defined before the bumper surface reaches the limiter; these are named as lower and upper hardware limit, negative and positive hardware limit or as hardware limit “min” and “max”. These defined limit positions are used by the software to limit the movement of the unit.

Because lost steps are unwanted during the scan procedure and normal work, the “Hardware limit” position has to be defined before the bumper surface will reach the hardware limiter; the hardware limit position itself is a part of the real movement range.

· Usually we can say, the start point of the unit is the negative limit and the endpoint of the possible movement range is the positive limit.

Accuracy of the defined limit

The accuracy of the defined hardware limit position depends on the unit; in the X-Y-stage unit for example, the accuracy is 0.1mm (100µ-steps) during in other units, like the camera changer or the focus unit, the accuracy of the limit is 10µ-steps.

This means, the distance of the bumper surface to the limiter is 0.1mm or less, but the bumper surface never bumps against the limiter; lost steps must not occur.

· The step number of the hardware limit is always defined before steps are lost!

· All the used hardware limit positions for the units are collected in the section “[HardwareLimits]” of the file “MicroscopeConfiguration.ini”.

On the other side, to find the correct hardware limit, we are creating lost steps first (with the service program), and then we reducing the number of steps by the allowed accuracy (100steps or 10steps) until lost steps do not occur during the movement of the unit.

· Check the found hardware limit by moving the unit more (3) times from the position Home1,2 to the found limit position and return to Home1,2. During these movements, lost steps should not be experienced (not more then +-2steps).

· Move also the mechanical drive against the limiter until lost steps are produced. With the service program, the unit should be able to leave the jammed position if the unit is moved some 100 steps in direction to Home1,2. If jamming occurred and the unit can not be moved away from the limiter, the unit is faulty (or adjusted wrong). During this check please do not use the button “Home1” because the timing and control of the motor steps is often different between normal move and searching for Home1.

The values, where the limit positions of the appropriate unit can be found are different from unit to unit of the same type also, so an interval is defined.

Each unit of the same type has its limit “min” and “max” in the defined range (the limiter position range, LPR), outside the guaranteed movement range.

Movement ranges and limits

Maximal movement range

The maximal movement range is defined by the behavior of the sensor “Home1” and is always larger than the real movement range.

· If the moving part of the unit can be moved behind the specified value of the maximal movement range (the limit “Home1”), the unit is faulty.

Guaranteed movement range

· The guaranteed movement range is defined by the requirements of the moveable unit to fulfill its task; it may be 1revolution, several 10 revolutions until over 200 revolutions of the motor axle.

· The guaranteed movement range is defined by the number of revolutions of the stepper motor axle.

· In exceptions, it is prolonged by some 100 steps in any direction by shortening the limiter position range (LPR).

· In exceptions the upper limit may be shortened if collision of components would occur.

P250 hardware limit Y-max and SCAN hardware limit Y-max

Position Home1,2

The home position of the entire mechanical drive, the start position for counting motor steps, is defined inside the guaranteed movement range. Starting from this position, the rotor steps are counted in positive or negative direction.

Real movement range

· The real movement range is always larger then the guaranteed movement range, it is limited by the found hardware limiter positions; before the bumper surface contacts the limiter; except the camera changer unit and the focus unit.

· The absolute value of the negative limit of the real movement range is less than or equal to the negative limit of the maximal movement range (the limit “Home1”).

· The positive limit of the real movement range is less than or equal to the positive limit of the maximal movement range (the limit “Home1”).

Limiter position range (LPR)

The hardware limiters for the positive and the negative limit of the unit are physically found in this range.

The physical position of the limiters and the bumper surfaces are always exactly on the same place in the unit, therefore, if the negative limit is found correctly, the positive limit will always fulfill the requirement of the limit “Home1”; but because the mounting position of the spindle in relation to the rotor axle is variable (X- and Y-drive unit) and the found thread starting position of the transport nut is defined with an accuracy of 800steps, the real hardware limit value may be anywhere in this range.

· The found hardware limit values define the real movement range.

“Exchange the Y-drive of the X-Y-stage unit” and “Before we can mount the drive unit”

In the focus unit

In the focus unit the hardware limit values depending highly on the found ex-center position on the motor axle.

in the P250: “Adjust the ex-center position”

SCAN, MIDI, DESK: “Adjust the ex-center position”

· In the SCAN, the MIDI and the DESK the shown position is exact 1600steps.

In the camera changer unit

In the camera changer unit the “Variable position” of the guaranteed movement range depends on the found clutch mounting position on the motor axle; so the pin connection may be in different positions in relation to the home position of the rotor. Therefore, the home position Home1,2 will be only in exceptions in the center of the guaranteed movement range.

Sensor “Home1” and hardware limits

This chapter describes the role of the sensor “Home1” during the definition of the hardware limits.

· If the mechanical drive is moved in direction to the “max” (positive) limit, the rotor of the stepper motor rotates forward (CCW); the step number of the step counter will be increased.

· If the mechanical drive is moved in direction to the “min” (negative) limit, the rotor of the stepper motor rotates backward (CW); the step number of the step counter will be decreased.

Important remark

The hardware limits are always defined as a number of steps, done in the positive or negative direction, counted from Home1,2.

During stepping in positive direction, the “Rotor position” is identical with the “Number of steps” gone!

· If we are doing steps in negative direction, the “Number of steps” gone is different from the “Rotor position”!

· The service program shows always the step counter content, not the rotor position

· The value of the appropriate hardware limit is always the “Number of steps”; in “our” step counter example above the lowest value would be -1599! And not 1601!

Home sensor “Home1”

The implementation of the sensor “Home1” defines the main restriction in question of all the hardware limits.

Depending on the actual step number of the step counter, the rotor rotates forward (CCW) or backward (CW) respectively to find the position “Home1”.

· If the step number of the step counter is in the range from +0001 to +1600 (or a multiple number of +3200steps) and the command “Home1” is issued, the rotor is moved backward (CW) to find the position “Home1”.

· If the step number of the step counter is in the range from -1 (rotor position 3199) to -1599 (rotor position 1601) (or a multiple number of +3200steps) and the command “Home1” is issued, the rotor is moved forward (CCW) to find the position “Home1”.

· If the step number of the step counter stays in the position “0000” (identical with “3200”) or a multiple number of revolutions, the rotor is moved only about 10 steps backward and forward again until the correct transition of the sensor “Home1” is found, practically a movement of the rotor axle is not experienced.

· Because we allowing a maximal tolerance of +-2steps in the found home position, and the position 1600steps of the rotor is critical for the sensor “Home 1”, this position should be clearly in distance to the found hardware limit!

Remark

The explanation above is true if we assume that the revolution of the rotor is done in 3200steps; the position of 1600steps defines exact a half revolution. If the revolution is done in 6400steps, the number of steps for a half revolution is also twice, 3200steps. The sensor “Home1” works always with a half revolution!

“Sensors Home1,2”; and “Sensors”.

Negative limit

The rotor rotates in backward direction (CW), seen from the state “Home1,2” (the steps are counted in backward direction also; the step number in the step counter will be decreased) until the rotor position “1601” is reached (1599 steps are done in negative direction; backward). If we are issuing the command “Home1” in these rotor positions (between the rotor positions 3199 and 1601), the rotor will move in forward direction (CCW) to find the home position “Home1”; the rotor moves the mechanics away from the limiter.

If we would allow more steps to go in backward direction, the construction would overstep the border of the rotor position of “1600” (the step counter content would be less than or equal to 1600 steps) and, if we issuing the command “Home1” the rotor would move more backward to find the position “Home1” and mechanical jamming of the construction would occur; the moving part would be moved against the limiter and lost steps would occur.

· The absolute negative limit (defined by the limiter) is always less than 1600steps in negative direction, counted from Home1,2 (lost steps have to be generated before the rotor position of 1600steps is reached); otherwise the unit is faulty (or adjusted wrong; please refer to the chapter “Limiter position range”)..

Positive limit

The mechanics moves in direction to the positive limit, (the rotor moves forward, CCW).

The number of steps in the step counter will be increased and, if the guaranteed movement range is passed, the sensor “Home1” defines also the possible number of steps to go; this number is also less than 1600steps.

The rotor rotates in forward direction, seen from the state “Home1,2” until the step number “1600” is reached after the specified number of revolutions is executed. If we are issuing the command “Home1” in these positions (between 0001 and 1600 after the guaranteed movement range), the rotor will move in backward direction (CW) to find the home position “Home1”; the rotor moves the mechanics away from the limiter.

If we would allow more steps to go in forward direction, we would overstep the border of 1600 steps (the rotor position would be higher than 1600 steps) and, if we issuing the command “Home1” the rotor would move forward to find the position “Home1”, mechanical jamming of the construction would occur; the moving part would be moved against the limiter and lost steps occur.

· The absolute positive limit (defined by the sensor “Home1”) is always less than 1600steps in positive direction after the guaranteed movement range is passed, counted from Home1,2 (lost steps have to be generated before the rotor position of 1600steps is reached); otherwise the unit is faulty (or adjusted wrong; please refer to the chapter “Limiter position range”).

Remark

Because we are allowing a tolerance of 2steps, the hardware limit in the position 1600steps of the sensor “Home1” is critical and should never be used. In other words, the found hardware limit position should be always clearly less then 1600steps.

If the resolution of the motor is 6400 steps, the border value of 1600 steps is also changed to the value of 3200steps. In other words, we using always exact a half revolution of the rotor to define the limit of the sensor “Home1”.

“Sensors Home1,2”; and “Sensors”.

File “MicroscopeConfiguration.ini”

· Please make a security backup of the file “Microscope Configuration.ini” before modifying values!

The file “MicroscopeConfiguration.ini” will be found in the folder:

In the software version 1.14 (Windows XP): C:\DocumentsAndSettings\AllUsers\ApplicationData\3DHISTECH\SlideScanner\

In the software version 1.15 or higher (Windows 7): C:\ProgramData\3DHISTECH\SlideScanner\

In earlier software versions: The file “MicroscopeConfiguration.ini” or “Config.ini” is situated in the same folder as the scan program; the filename of the scan program was “Mscan.exe”. Please use the file search option of Windows and search for the file MicroscopeConfiguration.ini or “Config.ini”.

SlideScannerSercie.exe and Paths and locations

· To edit the parameter values of the file “MicroscopeConfiguration.ini” the program “WordPad” or “Notepad” should be used.

· Save the file “MicroscopeConfiguration.ini” without any formatting information, as a *.txt-type file (text only)!

Section [HardwareLimits]

All the used hardware limit positions for the units are collected in the section “HardwareLimits” of the file “MicroscopeConfiguration.ini”.

· Depending on the scanner type and the configuration, not all the parameter values are used.

· Other sections of the file “MicroscopeConfiguration.ini” may also be affected by the found hardware limit; please see the appropriate unit.

Techniques to define hardware limits

Using lost steps

Start the service program and set the appropriate unit to its home position.

To find the hardware limit of the unit in question, we always producing lost steps first, then we decreasing the absolute number of steps to go by the number of steps with the limit accuracy until lost steps do not occur.

· The first number of steps that do not produce lost steps is used as hardware limit.

· Always check and define the negative limit first, then the positive limit.

· Limit adjustments are always done with the negative limit position!

1. Set the appropriate unit to its Home1,2 position.

2. Start with a step number outside the guaranteed movement range.

3. Move the unit to the start position and go backward the same number of steps.

4. Press Home1 only.

5. If there are not more than 2 steps difference to Home1, increase the number of steps by the accuracy of the limit (100 or 10steps) and repeat from step 1. In the step 2 use the actual absolute number of steps (because lost steps are not experienced, the possible movement range is larger than we assumed)!

6. If there are more than 2 steps difference to Home1, decrease the number of steps by the accuracy of the limit (100 or 10steps) and repeat from step 1. In the step 2 use the actual absolute number of steps (because lost steps occurred, the possible movement range is smaller than we assumed)!

Remark

· The starting number of steps to find the negative limit is outside of the guaranteed movement range, I prefer the use of 1300steps (X- or Y-stage).

· The starting number of steps to find the positive limit is also outside of the guaranteed movement range, it should be higher by some 100steps.

· In all cases, even if the found limit number is in the near of the maximal movement range, the correct working of the home sensor “Home1” should be checked painstakingly.

Example to find the negative limit in -X-direction

1. With the service program set the Y-carriage to Home1,2.

2. Set the X-carriage to Home1,2.

3. With the service program go forward to the X-motor position -1300 steps.

4. Go backward +1300 steps.

5. Press Home1 (only). There should be not more than +-2 steps difference to Home1. If there are more steps lost, decrease the actual absolute number of steps by 100 and repeat from step 2. In the steps 3 and 4 use the actual absolute number of steps!

6. If there are not more than 2 steps difference to Home1, increase the number of steps by 100 and repeat from step 2. In the steps 3 and 4 use the actual absolute number of steps!

7. The negative limit is found correctly if the motor movement has no steps lost and the actual absolute number of steps, increased by 100 would produce lost steps.

8. Update the value of the parameter “ObjectGuideXMin” in the file “MicroscopeConfiguration.ini” section [HardwareLimits] with the found number of the actual steps and save the file.

Remark

The found negative limit can differ by more 100steps from unit to unit. The reason is the spindle fixing position on the motor axle and the found thread starting position of the spindle in relation to the transport nut.

Example to find the positive limit in +X-direction

9. With the service program set the X-carriage unit to Home1,2.

10. Go forward to the X-motor position +29700 steps.

11. Go backward 29700 steps.

12. Press Home1 (only). There should be not more than +-2 steps difference to Home1. If there are more steps lost, decrease the actual number of steps by 100 and repeat from step 9. In the steps 10 and 11 use the actual number of steps!

13. If there are not more than 2 steps difference to Home1, increase the number of steps by 100 and repeat from step 9. In the steps 10 and 11 use the actual number of steps!

14. The positive limit is found correctly if the motor movement has no steps lost (max. 2 steps) and the actual number of steps, increased by 100 would produce lost steps.

15. Update the value of the parameter “ObjectGuideXMax” in the file “MicroscopeConfiguration.ini” section [HardwareLimits] with the found value and save the file.

16. Check the found limits by using the number of steps, used as parameter value in the file “MicroscopeConfiguration.ini” section [HardwareLimits]. Lost steps have not to occur.

Remark

The found positive limit can differ by more 100steps from unit to unit. The reason is the spindle fixing position on the motor axle and the found thread starting position of the spindle in relation to the transport nut.

Units and their hardware limits

X-direction; PCON

Parameters: [HardwareLimits] “ObjectGuideXMin”; “ObjectGuideXMax”

· The accuracy= 100steps (0.1mm)

Negative limit

-1500steps ≤ “ObjectGuideXMin” < Home1,2

Positive limit

28800steps < “ObjectGuideXMax” ≤ 30300

Other related or affected sections and parameters: none

“X-Y-stage unit” and “Find the hardware limits”

Y-direction; PCON

Parameters: [HardwareLimits] “ObjectGuideYMin”; “ObjectGuideYMax”

· The accuracy= 100steps (0.1mm)

Negative limit

-1500steps ≤ “ObjectGuideYMin” < -500steps

Positive limit

89600steps < “ObjectGuideYMax” ≤ 91100steps

Other related or affected sections and parameters: none

“X-Y-stage unit” and “Find the hardware limits”

X-direction; P250

Parameters: [HardwareLimits] “ObjectGuideXMin”; “ObjectGuideXMax”

· The accuracy= 100steps (0.1mm)

Negative limit

-1500steps ≤ “ObjectGuideXMin” < Home1,2

Positive limit

28800steps < “ObjectGuideXMax” ≤ 30300

Other related or affected sections and parameters: none

“X-Y-stage unit” and “Find the hardware limits”

Y-direction; P250

Parameters: [HardwareLimits] “ObjectGuideYMin”; “ObjectGuideYMax”

· The accuracy= 100steps (0.1mm)

Negative limit

-1500steps ≤ “ObjectGuideYMin” < -500steps

Positive limit

89600steps < “ObjectGuideYMax” ≤ 91100steps

Other related or affected sections and parameters: none

Important restriction!

To avoid collision of the slide clamp with the focus pin holder, the possible upper limit of the Y-carriage can not be used as hardware limit!

· Move the Y-carriage in direction to the limit “Y-max” until a gap of 0.1mm (= 100 steps) exists between the focus pin holder and the slide clamp (mounting)!

The value is found in the near of 89000 steps

Other related or affected sections and parameters: none

“X-Y-stage unit” and “Find the hardware limits”

Focus unit; P250

Parameters: [HardwareLimits] “FocusDeviceMin”; “FocusDeviceMax”

· The accuracy= 10steps

· The hardware limit’s values depending highly on the found ex-center position on the motor axle.

Negative limit

-3190steps ≤ “FocusDeviceMin” < -300steps

Other related or affected sections and parameters:

[Focus]; CondenserCoverOff

Positive limit

1300steps < “FocusDeviceMax” ≤ 3190steps

Other related or affected sections and parameters:

[Focus]; CondenserCoverOn

“Adjust the ex-center position” and “Find the hardware limits for the focus unit”

Remarks

The focus motor has a resolution of 6400steps / revolution; so the limit of “Home1” is defined by 3200steps.

The hardware limit is defined by the shutter wire and the shutter arm.

The real limit position depends on the adjusted ex-center position and may vary by some 10steps.

Camera changer unit; P250

Parameters: [HardwareLimits] “CameraChangerVT_Min”; “CameraChangerVT_Max”

· The accuracy = 10steps

· The hardware limit’s values depending highly on the found clutch-pin position on the motor axle; see “Variable position”.

Negative limit

-1590steps ≤ “CameraChangerVT_Min”;

“Movement limiters” and “Find the hardware limits”

Other related or affected sections and parameters:

[CameraChangerVT]; Position1=

“Define the mirror disc working position”

Positive limit

“CameraChangerVT_Max” ≤ 1590steps;

“Movement limiters” and “Find the hardware limits”

Other related or affected sections and parameters:

[CameraChangerVT]; Position2=

“Define the mirror disc working position”

Remarks

The “Variable position” means, the position Home1,2 is only in exceptions in the center of the guaranteed movement range.

On the other side, the construction must be fit always between the limits Home1!

· The positions “C”, the last position without lost steps, must not exceed the limits “Home1”; otherwise, the adjustment is faulty!

Reflector turret unit; P250 (belt driven)

Parameters: none

“Principle of the belt drive”

Other related or affected sections and parameters:

[ReflectorTurret]; StartingMotorPosition= see: “Find the first filter position”

Remark

Parameters: [HardwareLimits] “ReflectorTurretMin”; “ReflectorTurretMax” are not interpreted if the “ReflectorTurretType” in the section [Microscope] is set to “RT_3DH_10Pos_Belt”

ReflectorTurretType= RT_3DH_10Pos_Belt; see: “Configure the belt driven reflector turret unit”

“Find the Home position of the filter wheel” and “Check or adjust the external sensor acting range”

X-stage unit; SCAN, MIDI, DESK

Parameters: [HardwareLimits] “ObjectGuideXMin”; “ObjectGuideXMax”

· The accuracy= 100steps (0.1mm)

Negative limit

-1500steps ≤ “ObjectGuideXMin” < Home1,2

Positive limit

28800steps < “ObjectGuideXMax” ≤ 30300

Other related or affected sections and parameters: none

“X-Y-stage unit” and “Find the hardware limits”

Y-stage unit; SCAN, MIDI, DESK

Parameters: [HardwareLimits] “ObjectGuideYMin”; “ObjectGuideYMax”

· The accuracy= 100steps (0.1mm)

Negative limit

-1500steps ≤ “ObjectGuideYMin” < Home1,2

Positive limit

73600steps < “ObjectGuideYMax” ≤ 75100

Pannoramic SCAN

Important restriction!

To avoid collision of the slide clamp with the focus pin holder, the possible upper limit of the Y-carriage can not be used as hardware limit!

· Move the Y-carriage in direction to the limit “Y-max” until a gap of 0.1mm (= 100 steps) exists between the focus pin holder and the slide clamp (mounting)!

The value is found in the near of 73000 steps

· Use the found value as hardware limit Y-max!

Other related or affected sections and parameters: none

“X-Y-stage unit” and “Find the hardware limits”

Focus unit; DESK, MIDI, SCAN

Parameters: [HardwareLimits] “FocusDeviceMin”; “FocusDeviceMax”