index.md

How to assemble the bracelet

This section describes how the slim bracelet is put together.

Making the enclosure parts

There are two ways to make the parts for the bracelet.

First, using a home 3d printer. I used Prusa i3 MK3S printer with pretty good results. I printed the parts with PETG (Polyethylene terephthalate glycol). The disadvantage of this method is that it requires postprocessing: sanding and removal of support material.

Second, ordering the parts online with a Selective Laser Sintering (SLS) printer. The parts can be conveniently ordered on Shapeways or from other companies. It provides a much better result as it did not need any postprocessing.

The zip of for the parts can be downloaded here.

Adding the brass inserts

The next step is to add the brass inserts to the parts. The brass inserts hold the screws in place. Screwing could have been done without them, but they allow a reusable and robust screw interface. This requires the following things:

1. Soldering iron. I used the common Hakko FX888D-23BY with a special tip for heat inserts.

2. M2 x 3mm brass inserts. I got them on Amazon.

I heated up the soldering iron to 650 degrees Celsius. Then, I pushed the brass insert with the soldering iron tip into the holes.

Making the strap

I used a 1x12 inch velcro strap from Amazon.

First, cut off the buckle with scissors.

Place the strap end with the cut off buckle into the small hoop in the 3d-printed case. Make sure that the text (ENVISIONED) on the velcro end is facing the top.

Put a line of hot glue on the end of the strap. Pinch the strap end down to glue the two pieces of strap. This should be done right after applying the glue, before it gets cold.

Once glue cools down, cut a hole in the strap with utility knife.

The next step is to place the end of the flex PCB with the connector into the cut hole in the buckle.

Attach the actuators

Solder the individual linear resonant actuators (LRAs) to the flex PCB.

Add the pill-shaped actuator enclosures. The actuators come with the sticky back, which is exposed after removing the white cover paper.

After soldering and adding enclosures, flip the bracelet.

Screw on the actuator top. I used the M2 5mm hex screws.

The spacing between the actuators should be 0.25 inch.

Repeat for all 7 actuators. The finished actuators should look like this.

Assembling the main enclosure

Add the top cover to the enclosure. The cover is screwed with M2x5mm phillips screw.

Add the battery by pushing it into the enclosure. We used 100 mAh LiPo.

Solder and glue the enclosure LRA. We used additional tape to attach it, since the original one is not strong enough to hold LRA in place.

Connect the flex PCB connector and battery connector to the main PCB.

Screw the board with two screws using M2 5mm Phillips screws. Add a rubber washer between the screw and the PCB.

Attach the lid with two M2 5mm Phillips screws.