We had a need to prevent any accidental motion of our Dimension 3100's XY translation stage, so I made a simple modification
that allows us to turn off the X axis motion, Y axis motion or both. In addition, (and most important to us), a button on the
trackball must be held down to enable XY motion of the stage. This is similar to holding down the FOCUS or ZOOM button to enable those modes.
This modification is very straight forward, and only requires basic soldering and wiring. Do not attempt these modifications if
you are not qualified. We are not responsible for damage you do to your Dimension.
Overview
The XY translation stage has limit switches which stop the motion of the sample chuck near the edges of the granite.
These switches are normally closed, so when the chuck reaches the edge, the switch is depressed, and a circuit is opened,
which stops the motion. We will be using this feature in our modification by intercepting each of the four limit switches'
circuits and inserting our own switches in series.
The parts you will need for this modification are: large Phillips screwdriver, 10-20 feet of 4 conductor cable (I used
telephone cable), two single pole single throw (SPST) switches, several 2-4 conductor connectors, a soldering iron,
and a drill. The type of connectors
used by DI are similar to Molex 08-50-0114 crimp terminals
(Digikey WM2200-ND) and Molex
10-11-2053 (7880 Series) terminal housing
(Digikey WM2604-ND)
Getting started
The first thing you will need to do is shut down the Nanoscope software, turn off the IIIA controller, and turn off
the pump and illuminator box ("huff n' puff"). It is very important you turn off the controller before disconnecting
the cables. Now you can disconnect the cables from the back of the Dimension. The back cover is held in place with
8 large Phillips screws. I find it easiest to remove all but the top center screw, then remove the top center screw while
holding the back on with my other hand. The back cover on our microscope usually stays in place with all the screws out,
and must be carefully pried off. The back cover has a bunch of cables connected to the inside of it, but they are long enough
so that you can get your hands inside.
Adding your own connector
The next step is to pull off the X axis connector from the circuit board. The X axis connector is on the header labeled "J9".
To remove it, you bend back the wide retaining tab on the left side of the connector with a small screwdriver or your fingernail,
and pull the connector off with your other hand. You then need to remove the two black wires. The wire can be removed from the connector by pushing a jeweler's screwdriver or a thin knife into one of the slots
on the side of the connector. If you've never seen a connector like this, you may have to play with it a while to figure it out.
Once you have the black wires removed, insert it into one of your own connectors (easiest if you use a type compatible with
the one used by DI (see above for link to part numbers). Now do the same for the Y axis connector. You may wish to take note
of the original pin numbers of the black wires you are removing in case you want to restore it back to the original state.
On the each mate for the new connectors, solder one each of your 4 long wires. The other two long wires get crimp terminals
and one each gets inserted into the original DI connector in the location of one of the original black wires. See the
schematic
for details.
Modifying the trackball
The next step is to add the X and Y enable switches, and to modify one of the trackball switches labeled "lock" to be
used as an XY translation enable. Since I use only the left "lock" button on the track ball, I picked the right "lock" button
for my XY enable switch.
Disconnect the track ball from the serial port (COM1, 3F8, IRQ4 for those who know what that means). There are 4 Phillips
screws on the bottom which need to be removed. Take off the top and remove the trackball. Decide which of the two lock
switches you want to convert and find it on the back of the circuit board. I chose the right "lock" switch, so when the
board is flipped over, the switch is on the left. Cut a gap in the two traces going to this switch with a sharp knife. Now
solder on your own wires, two wires to each of the terminals of the switch. It may be helpful in later steps if you use at least
two different colored wires, if not four different colors.
Next, drill two holes in the trackball case for the X and Y disable switches. Put them where ever you want, but keep in mind
how the your switches, the case, circuit board and trackball have to fit together. I found a space in the back of the case
that didn't interfere with anything once assembled. See the pictures for an example.
When I tried to put the circuit board back in the case, I found I couldn't get my wires from the bottom of the circuit
board to the top, where my switches were. My solution was to drill a hole through the circuit board big enough for my wires to fit
through. Be careful to drill through an area that doesn't contain any circuit traces on either side, and that will not damage
any components on the top side.
The two wires from one side of the "lock" switch get connected to each of the axis disable switches. The other two wires from
the "lock" switch go through a hole in the trackball case to be connected to the 4 conductor cable. Two of the wires from the
four conductor cable connect to the other pole of the axis disable switches. See the schematic for details on which wire goes
where.
I wanted to be able to easily disconnect my four wire cable from the track ball, so I put another connector between the
trackball and the cable.
Reassemble the trackball and connect it to the computer. Close up the back of the dimension with your cable coming out the
hole at the top left. Connect all the microscope cables. It may be a good idea to tape the cable to the back of the dimension to prevent accidental pulling of
the cable. Now power up the Nanoscope IIIA controller, the "huff n' puff" and start the Nanoscope software. Go to realtime mode
and go to the stage translation mode. Remember to hold down the correct "lock" button to enable the stage motion. The two axis
disable switches will allow you to turn on or off the X axis, the Y axis or both.
Trouble shooting
Hopefully everything worked as I described, but in case it didn't here's where you can start to figure out what is wrong. Before
you begin checking connections, you should exit the Nanoscope software, turn off the Nanoscope controller and the
illuminator/pump box. It is not worth saving an extra minute by skipping this important step.
- The biggest problem I had was the trackball to cable connections. Make sure you have it wired according to the schematic.
Check your switch "logic" using a multimeter (continuity checker) on the wires leaving the trackball. If the switches are
connected properly and working like you expect, the problem is probably the way the four wire cable is connected.
- Double check the wiring inside the Dimension. Make sure your header is wired exactly as the schematic.
- The crimp terminals on the Dimension wires are pretty fragile. I had one of the limit switch wire connectors break off, and
several of the ones on my phone cable break off. Fortunately I had a bunch of spare crimp terminals to replace them with. This
is one good reason to use the same type of connectors as DI uses for your connectors. You have get some of these connectors
anyway to connect two of your wires to the DI header.
- One problem I had way very erratic
motion of the stage when using the trackball for
translation, and not motion at all when using the stage move
commands ("Motor at axis limit" error). This was caused by a
bad connection or improper connection on J3 and J5 on my
schematic. The two black wire should be connected together
on your connector. (see schematic).
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Here is a view of the XY stage
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With the cover off, you can see the limit switches. You don't need to do this, it's just
shown here for your information
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With the back cover removed you can access the connectors you need for the modification.
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A close up of the X axis and Y axis connectors you need to access
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Click the schematic for a larger (readable) version, or view the pdf.
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Trackball with top removed
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View of the back of the track ball circuit board. Carefully cut these circuit traces going to the "lock" switch". We will be soldering on our
own connections to this switch
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Solder on two of your own wires to each of the switch terminals. Using different wire colors will
help you figure out what wire goes where in later steps.
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Here is the back of the trackball with one of the axis disable switches installed. The switches will
interfere with stuff inside the case if you don't put them in a good location. The region I have marked is safe. Drill the
correct size hole according to the switch instructions.
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Both switches are installed and the two wires from the "lock" switch are connected to the axes
disable switches. We still need to connect the two wires coming from Dimension limit switches (the black wires from the limit
switches). See the schematic for the rest of the switch connections. Notice I drilled two small holes in the circuit board so I could bring
the wires from the bottom of the board to the top. You can drill these holes anywhere there are no traces or components on
either side of the circuit board.
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Finished trackball before assembly. Notice the connector at the top of the trackball to disconnect the
four wire cable from the trackball.
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