Cute Compute Cluster

Kalani Duran, Adam Grobman, Katharine Larsen, Kaveh Pezeshki

Overview:

Using the PCB files given in the Hackaday project terrible cluster, our team built a five-node Raspberry Pi Zero cluster on a custom backplane.

Motivation:

The goal of this project was to provide the team with a simple physical distributed computing platform for education: we wanted experience writing algorithms that can take advantage of multiple cores over a (very) slow interconnect. Additionally, it provided experience with surface-mount soldering, as the board included tight-pitch QFP ICs as well as many 0402 capacitors and resistors.

Assembly Process:

The PCBs were populated on an SMD rework station, complete with a hot air gun, microscope, and solder paste. We began by populating the PCB with 0402 passive components:

pcb-1

We next needed to solder the USB controller IC, via ample solder paste across the pads, hot air reflow, and finally a solder wick to remove bridges across pins. Some images of the assembly can be seen below:

micro-1 micro-2

After all surface mount devices had been added to the board, we then soldered the through-hole components:

pcb-2

The vertical USB headers were particularly difficult. Alignment was crucial in creating an attractive product, but the through-hole header pins were short and fragile. Our solution was to tape the headers in place prior to soldering.

pcb-3

At this point, the PCB was complete, and the Raspberry Pi Zeroes could be added. A Raspberry Pi Zero W serves as the head node, with Wifi as an external interface. The PCB successfully provided power and data communication between the five nodes:

final