Final Design

Design:

PCB and Data Transfer:

The PCB for our design allows us to transfer signal via USB 3.0 from one U-dot plate to another. The plate uses .5mm traces and utilizes two capacitors for removing noise in the power supply. All of our plates have identical mirroring PCB with female USB receptacles. This allows for easy connections to on board flight computers, payloads, or any other objects with data communication requirements aboard a spacecraft. Each conjoined plate will have one of the two mirrored PCB shown below, while its partner plate will have the opposite PCB.

Figure 1: Mirrored PCB A Figure 2: Mirrored PCB B

Each contact pad shown on the PCB is soldered to fuzz buttons which are placed in holes in dots in the U-dot plate and contact target pins in the U's of the opposite plate. Fuzz buttons, shown in figure 3, act as high performance pins, as they are a mesh of highly conductive material that can be shaped to fit your design and can be compressed like a spring.The data flows through the fuzz buttons and target pins allowing for data to be transmitted from one USB to the other. Note: our functional prototype utilizes pogo pins as opposed to fuzz buttons as lead times on fuzz buttons did not allow for the functional prototype to be manufactured on time.

Figure 3: Pogo Pins Soldered on PCB

Locking Mechanism:

For our locking mechanism, we are using a flex joint locking mechanism. This lock works by having a small protrusion in a flexible joint pushed aside by one of the dots and then snapped back into place behind the dot. Once the joint is snapped back into position the panels cannot be pulled apart until a lever is pulled which moves the protrusion out of the way so that the dot can slide past. In order to implement this design we added an extension to the side of one of the U's in order to mount the flex joint. Previous iterations of our locking mechanism were not auto-locking or fully captive, so this design greatly improves on alternative solutions. It also does not require any extra tools to operate.

Figure 4: flex joint locking mechanism

Figure 5: locking mechanism engaged

U-Dot Panel:

The final design for our panel is made out of sand-caste 7075 Aluminum. This is a quick manufacturing process that is relatively inexpensive and produces high quality results. Aluminum 7075 was shown through analysis (see performance section) to be plenty strong enough to withstand the roughest conditions during space travel while still being fairly light. We mounted our PCB to the plate using 2-56 copper screws with threaded inserts. The final CAD of the panel also includes a inset for the placement of the PCB onto the panel. The panel is also anodized using type 3 Anodization. This process electrically isolates the part and adds wear resistance.

Figure 6: full assembly of panel Figure 7: panel without assembly

Performance:

Electrical Performance:

The panel was able to run at USB 2.0 speeds without any issues. However; although we were able to get the panel to run at the maximum possible USB 3.0 speeds, it was not able to maintain the those speeds and often fluctuated to lower speeds. From observation, we were able to determine that this was caused by shearing on the pogo-pins slightly miss aligning them. This should not be a problem with the final aluminum panel, as the recommended fuzz buttons are resistant to shearing forces.

Figure 8: USB 2.0 download speed Figure 9: USB 3.0 download speed

Mechanical Performance:

We had no issues with the panel having strength issues even though we are only using abs plastic for the prototype. Because of this, we do not believe we will have any structural issues with the final aluminum version.

Figure 10: panels fully assembled and mated