TactionTablet - Tactile Tablet to Feel Images

This is a refreshable display that uses a single actuator instead of one actuator per pin.

• Metric allen wrench set
• Metric wrench set
• Plotter
• Feet
• Corner brackets
• 3 stepper motor kits
• Servo motor
• 8 M3x0.5x10 bolts
• 4 M5x40 bolts
• 9mm drill bit
• 7mm drill bit
• 5mm drill bit
• 3mm drill bit
• PLA
• Needle file
• Battery 
• Motor controller
• Arduino UNO
• Small Phillips head screwdriver
• Small gauge wire (ideally in four different colors)
• Red small gauge wire
• Black small gauge wire
• Red, black, and yellow jumper wires

The plotter kit should include two pieces of 1x1 extruded aluminum that are each 200mm long and three pieces of 2x1 extruded aluminum, one of which is about 200mm long and the other two which are about 300mm long. Take the two long pieces of extruded aluminum from the plotter kit and drill 6.75mm holes for the feet approximately 12.5mm from each end. Tap these holes using an M8 tap. The exact distance is not important.

Slide four of the corner brackets into the channels of the extruded aluminum forming a rectangle with two long sides of 2x1 extruded aluminum and two short sides of 1x1 extruded aluminum. With the holes that were just drilled and tapped pointed towards the table, the brackets should be placed in the upper channel. The brackets should be aligned such that the short pieces are inside the long pieces. Note that the corner brackets are not symmetric. In order for the short pieces to slide fully inside the long pieces, the side of the corner bracket with a longer flange must be inserted into the channel of the long piece. Once all the pieces are lined up, put eight of the set screws that came with the corner brackets into the threaded holes and tighten them down with an M2.5 allen wrench.

Screw one of the feet into each of the holes drilled in step 1

Slide two more corner brackets into the lower channels of each of the long pieces of 2x1 extruded aluminum. They will only slide all the way in if you correctly orient the side with the longer flange to be inserted into the aluminum. Furthermore, you want each of the L’s to be pointing towards the outside of the rectangle. Insert eight of the set screws that came with the brackets and begin to screw them in with an M2.5 allen wrench, but don’t tighten them all the way down yet. We want to maintain the ability to adjust the distance between them for now.

3D print two of “Overhang V3.STL”

These 3D printed supports should be bolted to the frame using the corner brackets inserted in step 4 using M4x22 button head cap screws. Make sure both the supports and the heads of the bolts are on the inside of the corner brackets. Put M4 nuts on the other side and tighten. The M4x22 screws we used came with the stepper motors. 

In the plotter kit, there should be two acrylic plates with pre-drilled holes for mounting a stepper motor. Even though the plotter kit comes with different stepper motors, the bolt size and distance between mounting bolts is the same, so these can be repurposed for our use. Mount one stepper motor to each of these plates using M3x0.5x10 socket head cap screws and tightening them down with an M2.5 allen wrench. Ensure that the white ports that the wires plug into are pointed upwards.

A special note about drop in t-nuts: in order for these to work properly, you always need the wide part to go into the channel first and the narrow part to stick up between the two sides of the aluminum.

Next we will attach the bearings for each of these stepper motors to the frame. Each bearing should go on a corner of the rectangle parallel with the short side. Put one M4x22 button head cap screws through each hole and put an M4 t-nut on each. Align one hole over the top-face channel of the 2x1 and the other over the top-face channel of the 1x1. Tighten down the bolts with an M2.5 allen wrench. Be careful to ensure that the bearing doesn’t twist while you tighten it and that it remains parallel with the short side of the rectangle.

Take two of the shaft couplers (from the stepper motor kits). Insert lead screws into the wider end of the shaft couplers and use an M2.5 allen wrench to tighten the set screws down. These screws must be tightened very well to prevent the shaft from slipping.

Insert the shafts of the two stepper motors you affixed to the acrylic mounting plates into the smaller diameter ends of the shaft coupler and tighten down well with an M2.5 allen wrench.

Take one of the motor/lead screw assemblies and slide the lead screw along the long side and through the bearing. Hold the motor and mounting plate assembly against the frame such that the lead screw is level. Use a marker to mark three places: the center of the hole aligned with the upper channel of the 2x1 extruded aluminum, the center of the hole aligned with the lower channel of the 2x1 extruded aluminum, and somewhere along the centerline of the channel of the 1x1 extruded aluminum approximately 25mm from the end of the 1x1.

Remove the motor and lead screw assembly from the bearing, unscrew the motor from the acrylic mounting plate, and set them aside. Drill holes where you made the marks on the acrylic mounting plates. The two holes aligned with the 2x1 aluminum should be drilled using a 7mm drill bit and the hole aligned with the 1x1 aluminum should be drilled using a 5mm drill bit.

Reattach the stepper motors to the acrylic mounting plates and slide the lead screw back through the bearing. Put an M4x12 socket head cap screw through the smaller hole and put an M4 drop in t-nut on the other side (keeping in mind the note in step 8). Press the plate against the base structure with the t-nut going into the channel of the 1x1. Tighten down this bolt with an M3 allen wrench. Then put M6x11 bolts in the other two holes and thread them into the holes in the end of the 2x1. Tighten them down with an M5 allen wrench. The M4 bolts and t-nuts will have come with the stepper motor kits. The M6 bolts come with the plotter kit.

Take the lead screw nuts out of two of the roughly triangular plates that came with the stepper motors and set them aside for now. Be very careful not to lose any of the hardware when you do so.

Mark the triangular brackets with two parallel lines such that they make a rectangle, but with one short side at an angle.

Cut each bracket along those lines. We used a bandsaw for this task, but this could also be done with an angle grinder or hacksaw. Set aside the cut off pieces of metal for use later.

Take the third, shorter piece of extruded aluminum (the “crossbar”) and lay the freshly cut brackets across it. Make a line on each bracket where the centerline of each channel of the 2x1.

Make a line down the center of the short side of the rectangle of each bracket. 

Use a 5mm drill bit to drill holes at each place where the lines cross.

Put the lead screw nuts back onto the brackets. The side of the nut that sticks out further should be on the outside and the “sandwich” on the bolt, starting from the head, should go split washer, bracket, split washer, nut. The best way to do this is to get the top bolt in the right order, tighten it down just a few turns to make it stay, get the bottom one set up and tightened just a few turns, then alternate tightening each one a few turns at a time until both are screwed in all the way.

Put an M4x8 button head cap screw through each of the freshly drilled holes such that the button head is on the side closer to the lead screw nut. Put an M4 drop in t-nut on the other end of teach bolt (but don’t tighten it down). Be sure to pay attention to the orientation of the t-nut as described in step 8. The cap screws and t-nuts should both have come in the stepper motor kits.

Unscrew the lead screw side of  each of the shaft couplers and slide the lead screws out a little ways. Thread the brackets onto the lead screws through the lead screw nuts.

Slide the crossbar on top of the brackets such that the t-nuts slide into the channels. Tighten down the bolts with an M2.5 allen wrench.

Laser cut “(2022-11-07) X Axis Motor Mount.DXF” from ⅛” acrylic. Upload the file to your laser cutter and use the following settings: Power: 100%, Speed: 6%, PPI: 5000. Cut one copy.

Bolt the third stepper motor to this plate using the M3 bolts that came with the plotter kit. It’s important to use these rather than the other ones because the other ones are longer and will bottom out against the motor. Another solution would be to use a spacer in between the bolt and the acrylic plate. You might need to use a needle file to widen some of the holes in order to put all four bolts in. Make sure the port for the wires to connect is pointed downward.

Bolt the plate with the motor mounted to it to the end of the crossbar using M6x11 bolts from the plotter kit and tighten them down the an M5 allen wrench.

Laser cut “(2022-11-07) X Axis Bearing Mount” from ⅛” acrylic. Upload the file to your laser cutter and use the following settings: Power: 100%, Speed: 6%, PPI: 5000. Cut one copy.

The piece you’ve just laser cut is the mounting plate for the x-axis bearing. Put two M5x10 bolts through the bigger holes and put an M5 t-nut on the other end (paying attention to the orientation as described in step 8). Slide the t-nuts into the opposite side of the crossbar from the motor. Slide the plate just far enough in that the t-nuts are completely inside the channels, then tighten them down with an M4 allen wrench.

Put M3x24 bolts through the holes in the plastic bearing casing and the smaller holes in the mounting plate and secure with M3 nuts on the other side using an M2.5 allen wrench.

Put the last shaft coupler on the third lead screw and tighten down firmly using an M2.5 allen wrench.

Slide the screw through the bearing and put the other end of the shaft coupler on the motor shaft. Tighten down firmly using an M2.5 allen wrench.

3D print four of “(2022-11-24) Small Wheel Spacer.STL”, one of “(2022-11-24) X Axis Carriage.STL”, and one of “Servo Bracket.STL”

Take the lead screw nut off the bracket from the third stepper motor kit and screw it into the inside pillar of the x-axis carriage. Which direction the lead screw nut is inserted in is not important, but make sure the bolt goes through the objects such that the order is split washer, plastic, split washer, lead screw nut. You may need to use a needle file to enlarge the bolt holes slightly depending on the precision of your 3D printer.

Slide the servo bracket over the servo such that it sits in between the shoulder of the servo and where the wires come out. It should be quite snug. Use M5x18 socket head cap screws to attach the servo bracket to the x-axis carriage. Tighten it down with an M5 nut and an M4 allen wrench. You can either get M5x18 bolts, or, if you have access to an angle grinder, you can use the M5x30 bolts that come with the plotter kit and cut them down with an angle grinder.

Put a bolt through one of the holes at the base of the carriage and stack things onto it in the following order: 

• Small Wheel Spacer
• Wheel from the plotter kit
• Nylon spacer from the plotter kit (diameter: 9mm; length: 12mm)
• Wheel from the plotter kit
• Small Wheel Spacer

Then put it through the hole on the other side and secure it with a nut. Repeat for the other set of holes in the carriage. The size of this bolt is relatively arbitrary as long as it has a small diameter. We used one we happened to have on hand (6-32x3in that we cut down to about 2in), but you could also get some specifically for this. M3x50 would be a good metric option. 

Loosen the set screw on the x axis shaft coupler and slide the lead screw out a little. Thread the x-axis carriage onto the lead screw through the lead screw nut such that the arm of the servo is pointing away from the y-axis motors. Then reattach the lead screw by tightening the set screw on the shaft coupler.

Use M4x8 button headed cap screws and M4 t-nuts to attach two of the plastic angles from the stepper motor kits to the upper channel of the long aluminum pieces of the base on the side further away from the x-axis motor and one of the plastic angles on the opposite side. These should be the plastic angles that have one hole in each side, not the ones that have two. The narrow half of the angle should be against the aluminum and the wide half should be parallel with your working surface. The smooth side should be facing down. Tighten the bolts a little bit using an M2.5 allen wrench, but not all the way such that you can still adjust the distance between them. It may be useful to temporarily take the entire crossbar assembly off.

Cut out a 150mmx200mm piece of MDF (either by laser cutting or whatever other method you prefer). Lay out two motor controllers, the Arduino UNO, and the battery on this panel. The battery should have its long side aligned with the 150mm side of the panel and be far off to the right side. To the left of the battery, there should be two motor controllers next to each other in the top half and the Arduino UNO in the bottom half. The motor controllers should have the terminals towards the Arduino and the heat sink towards the edge of the panel. The Arduino should be oriented with the port for loading code facing towards the outside of the panel. Once you have everything laid out, take a marker or pen and draw marks where all of the holes in the motor controllers and Arduino are. Also mark two large circles on either side of the battery such that the four marks form a rectangle.

Drill holes on all of the marks you just made. The marks from the motor controllers and Arduino should be drilled as 3mm holes. The holes on either side of the battery should be 9mm.

Bolt down the motor controllers using four M3x12 button head cap screws on each controller. Tighten them down using an M2.5 allen wrench and M3 nut. The Arduino has slightly smaller holes, so you will need to use four M2.5x16 button head cap screws and tighten them down with an M2 allen wrench and M2.5 nut. Use zip ties run through the larger holes drilled to secure the battery to the panel.

Flip the entire structure upside down and gently let it rest on the plastic supports. Place the electronics panel on top of the brackets that were affixed to the base structure in step 38 such that the electronic components are facing downwards. Adjust the positioning of the brackets such that the hole of the bracket on the side with only one is approximately centered on the panel and the holes of the brackets on the other side are relatively evenly spaced. Tighten down the bolts to fix the brackets in those positions. Use a marker to trace those holes onto the MDF.

Drill 4mm holes centered on each of those marks. 

Affix the panel to the brackets with three M4x12 countersunk Phillips head screws, which come in the stepper motor kits. Tighten them down with a Phillips head screwdriver (also in the stepper motor kit) and M4 nuts.

The next few steps walk through the wiring step by step. On the last wiring step, there is a table summarizing.

Using a 4 wire wide female to male ribbon cable, connect the In1, In2, In3, and In4 pins of the motor controller closer to the battery to pins 2, 3, 4, and 5 on the Arduino. Repeat this with another ribbon cable on the other motor controller connecting the In pins to pins 8, 9, 10, and 11 on the Arduino.

Cut eight wires, about 100mm long. We recommend using four different colors to distinguish between the different pins. Strip both ends of each wire. Insert one of each color into the Out screw terminals and use a small Phillips head screwdriver to screw in the terminal and fasten the wire down.

If you are using stranded wire, you will need to solder either a small length of solid core wire (as we have done here) or some sort of header pin to each wire to allow them to interface with the stepper motor cords. We recommend covering the joints with heatshrink.

Connect the wires from the motor controller closer to the battery to one of the stepper motor wires such that Out 1 and Out 2 are next to each other and Out 3 and Out 4 are next to each other. Then connect the two other ends of the cord to both of the y-axis motors.

Connect the wires from the other motor controller to a second stepper motor cord similarly to step 48 and connect the other end of the cord to the x-axis motor. 

Cut two lengths of wire (preferably red) that are each about 150mm long. Strip both ends of both wires and screw them into the +12V terminals on the motor controllers. Solder together the end of each of the two wires to create a single point of voltage in.

Take a red jumper wire and connect the +5V terminal of one motor controller (it doesn’t matter which one) to the VIn pin of the Arduino.

Cut two lengths of wire (preferably black) that are each about 150mm long. Screw them into the GND terminals of each of the motor controllers. Connect a black jumper wire to a GND pin of the Arduino and cut off the header pin on the other end. Strip the wire to expose the bare wire and solder all three of these wires together to create a single point of ground.

Put the crossbar back on if you removed it while working on the electronics panel. 

Plug in the servo. Plug a black jumper wire into the brown servo wire and one of the GND pins of the Arduino. Plug a yellow jumper wire into the yellow servo wire and pin 6 of the Arduino. Plug a red jumper wire into the red servo wire and the +5v pin of the Arduino.

Arduino Pin Connected To 2 In1 of motor controller 1 3 In2 of motor controller 1 4 In3 of motor controller 1 5 In4 of motor controller 1 6 Signal of Servo 7 NONE 8 In1 of motor controller 2 9 In2 of motor controller 2 10 In3 of motor controller 2 11 In4 of motor controller 2 GND GND of servo and ground bundle VIN 12V bundle 5V VIN of Servo

Plug the Arduino into your computer with the Arduino software and upload the code Proof_of_Concept to the Arduino. Use alligator clips to connect the bundle of ground wires to the ground of the battery and the bundle of 12V wires to the positive of the battery. This will cause the code to start and allow you to verify if everything is hooked up correctly.

Laser cut the following parts out of ⅛” acrylic 

Upload the file “(2022-11-30) Reset Panel v2.DXF” and “(2022-11-30) Reset Panel Slot.DXF” to your laser cutter.  Set the controls to the following: Power - 100%, Speed - 5.6%, PPI- 1000 (Note: See READ ME file)  Laser cut one (1)  copy of the Reset Panel and four (4) copies of the Reset Panel Slot. 

And the following parts out of MDF

Upload the file “(2022-11-30) MDF Grid  v2.DXF” to your laser cutter. Set the controls to the following: Power - 100%, Speed - 4.7%, PPI- 1000 (Note: See READ ME file) Laser cut two (2) copies of the file on the ¼” of MDF.

3D print the following files

4x “(2022-11-30) Lower Pin Grid Spacer”

4x “(2022-11-30) Upper Pin Grid Spacer”

2x “(2022-11-30) Reset Panel Guard Rail”

1x “(2022-12-07) Grid Backing”

Bolt one of the MDF grids to the supports with the bolt pointed up. One side should use the offcuts from the brackets in step 17 as spacers, so the layers go support, spacer, MDF. The other side should have support, backstop, MDF. Use four M5x40 bolts and M5 nuts to attach those layers.

Build up the layers of the pin grid affixing them together with an M5x44 bolt at each corner. The easiest way to do this is to put a bolt through each corner and put a nut on each to hold it in place. One corner at a time, remove the nut, add the next layer, and replace the nut. Continue this process until you’ve put all the layers together. The order of the layers (from bottom to top) is: 

• MDF Grid
• Large Grid Spacer
• Reset Panel Slot
• Reset Panel Guard Rail
• Reset Panel Slot
• Small Grid Spacer
• MDF Grid

Using the same lasercutter specifications as the previous step, cut out about 1100 pins on the remainder of the ⅛” acrylic.  (The pin board only has 930 holes but there is a chance you will get some defective pins so it's safer to just cut out extra)

Place one pin in each square hole with the flexible clip part facing away from the back stop