Assembling the Eyewriter 2.1 hardware platform (rev B)
This Instructable will guide you through the assembly of a hardware platform (rev B) to support the new Eyewriter 2.1 open-source eye-tracking system.

For more information about the Eyewriter project in general, visit the official site at http://eyewriter.org/

For more information abut the Eyewriter 2.1 update that I am working on, check out all of my blog posts related to it: http://jason-webb.info/tag/eyewriter-2-1/

I am also maintaining a condensed wiki page for the project here: http://jason-webb.info/wiki/index.php?title=Eyewriter_2.1

If you'd rather watch a video showing the assembly process, one is available on Vimeo here: https://vimeo.com/77366693

This Instructable got Featured, which earned me three free months of Pro membership! This means that I can now embed the actual assembly video here for you :)


Step 1: Gather all of the parts

Assembling the Eyewriter 2.1 hardware platform (rev B)
Assembling the Eyewriter 2.1 hardware platform (rev B)
The hardware platform consists of two types of parts: 3D-printed parts and hardware.

All of the printed parts are available at this Thingiverse page. Printing instructions are also available on that page.

Printed parts
- 2 x end blocks
- 3 x platform clips
- 3 x extension arms
- 2 x glint modules
- 1 x main board mount

Look for these hardware items at your local hardware store. But if you live in a place that does not have many metric parts, I've included McMaster part numbers so you can buy them online.

Hardware
- M8x~20" threaded rod (McMaster: 99055A125, cut to size)
- 4 x M8 nuts (McMaster: 90592A022)
- 2 x M8 lock washers (McMaster: 97985A590)
- 8 x M3x14 machine screws (McMaster: 91420A517)
- 6 x M3 lock washers (McMaster: 91120A120)
- 6 x M3 wing nuts (Grainger: 26L006)
- 2 x M3 nuts (McMaster: 90592A009)
- 1-3 x M3x20+ bolt (McMaster: 92005A128)

Making the threaded rod
You can make your threaded rod any length you want, but I find that ~20" works well for clamping onto laptops and 17" or 19" LCD screens. If you are not able to directly buy an M8 threaded rod at the size you need, you can easily make your own (if you have access to the right tools).

Measure your rod to the length you want, then cut it to length using a chop saw. This will result in a rough edge, which is not only dangerous, but impossible to thread a nut onto.

Use a bench grinder to smooth the end of the rod out and give it a little bit of a taper. Make sure to test out both ends (cut and uncut) by threading an M8 nut to see if you need to do any more work.

Step 2: Add M8 nuts to threaded rod for end blocks

Assembling the Eyewriter 2.1 hardware platform (rev B)
Thread one M8 nut onto each end of the threaded rod, and thread them until they are about 2-3" from the end.

Step 3: Add end blocks, M8 lock washers and out M8 nuts

Assembling the Eyewriter 2.1 hardware platform (rev B)
Add end block to each end, with captive M8 nut hole facing inward.

Add M8 lock washer and thread another M8 nut to hold the end blocks in place.

Step 4: Tighten outer M8 nuts to prevent twisting

Assembling the Eyewriter 2.1 hardware platform (rev B)
Tighten the outer M8 nuts nice and tight to hold the end blocks in place and prevent twisting.

If you ever experience twisting of the platform in the future, just tighten these outer nuts again!

Step 5: Both end blocks added.

Assembling the Eyewriter 2.1 hardware platform (rev B)
Make sure your end blocks and threaded rod look like the picture attached to this step.

Step 6: Snap on three platform clips

Assembling the Eyewriter 2.1 hardware platform (rev B)
Snap on three platform clips. This will take some force, which is good!

If any of the platform clips spin too easily around the rod, you may want to add a longer M3 bolt and nut through the small hole on the flange of the clip. You can tighten the nut to add more pressure on the clip, causing it to grip the threaded rod better.

Reverse one of the outer platform clips so that the glint module mount will face the right way!

Step 7: Attach extension arm to one of the platform clips

Assembling the Eyewriter 2.1 hardware platform (rev B)
Assembling the Eyewriter 2.1 hardware platform (rev B)
Add a M3 lock washer to an M3x14 machine screw, then thread it through an extension arm and one of the platform clip holes. Hold it in place using an M3 wing nut.

Refer to the photos to see how it all fits together.

Step 8: Attach the rest of the extension arms

Assembling the Eyewriter 2.1 hardware platform (rev B)
Repeat what was shown in Step 7 to attach extension arms to the remaining two platform clips.

Step 9: Attach left glint module mount to left-most extension arm

Assembling the Eyewriter 2.1 hardware platform (rev B)
Attach one of the glint mounts to the left-most extension arm. Make sure that it is angled towards the center of the threaded rod (see later pictures to see what I mean).

Attach the mount the same way the extension arms were attached to the platform clips. That is, with an M3x14 machine screw, lock washer and wing nut.

Step 10: Attach right glint module mount to right-most extension arm

Assembling the Eyewriter 2.1 hardware platform (rev B)
Attach one of the glint mounts to the right-most extension arm. Make sure that it is angled towards the center of the threaded rod (see later pictures to see what I mean).

Attach the mount the same way the extension arms were attached to the platform clips. That is, with an M3x14 machine screw, lock washer and wing nut.

Step 11: Attach the main board mount to the center extension arm

Assembling the Eyewriter 2.1 hardware platform (rev B)
Attach the main board mount to the center extension arm. Make sure that the mount is facing towards the converging point of the two glint module mounts. Refer to pictures in later steps for more clarification.

Attach the mount the same way the extension arms were attached to the platform clips. That is, with an M3x14 machine screw, lock washer and wing nut.

Step 12: Add M3 machine screw and wing nut to add pressure to platform clip

Assembling the Eyewriter 2.1 hardware platform (rev B)
I noticed that my main board (with the camera) is heavy enough to cause the center platform clip to spin around the threaded rod. Use a longer M3 machine screw (maybe about 20mm) through the holes in the flanges of the center platform clip, then tighten a wing nut to apply more pressure onto the rod.

Step 13: Insert and attach main board

Assembling the Eyewriter 2.1 hardware platform (rev B)
Assembling the Eyewriter 2.1 hardware platform (rev B)
Insert the main board into the main board mount (LED's face forward), then use two M3x14 machine screws with nuts to hold it in place.

?Prototype rev A electronics shown!

Step 14: Snap in the glint modules

Assembling the Eyewriter 2.1 hardware platform (rev B)
Assembling the Eyewriter 2.1 hardware platform (rev B)
Attach the glint modules into their mounts by gently snapping them into place.

Make sure that the interconnect jack is on the right side!

Prototype rev A electronics shown!

Step 15: Add interconnects to all boards

Assembling the Eyewriter 2.1 hardware platform (rev B)
Assembling the Eyewriter 2.1 hardware platform (rev B)
Connect each of the boards together using the interconnects.

Prototype rev A electronics system shown.

Step 16: Finished!

Assembling the Eyewriter 2.1 hardware platform (rev B)
Your hardware platform is now complete! You should be ready to install the camera and start working with the software!

If the threaded rod ever starts to spin freely (causing everything to fall over), just tighten the outer M8 nuts on the rod to apply more pressure to the end blocks!
 
 

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