Week-10

Fabricating an Arduino Uno Shield

Designing the PCB

The function of the PCB was to multiply the 5V and GND pin outputs for the Arduino UNO Rev3 in the context of our Fab Challenge 4 (full documentation here and on Github). This was necessary to provide an apt amount of available headers for the 12+ control units that will be connected to that single Arduino. After working with Fritzing before in Week 6 (Electronics Design), I gave it another shot but was (again) disappointed by the UX and lack of control over some critical parameters, such as trace width. Then I switched to Illustrator, which is much more bare-bones (because it doesn't offer any kind of presets), but allows an unprecedented control over everything. It's important to note that this is also precisely the reason why it doesn't prevent you from making critical mistakes, such as defining a prohibitively narrow clearance for the 1/64" drill or just simply setting the wrong design ratio overall. Additionally, I designed the board in an inverted way for the female headers to be soldered from the bottom (more on that below), so the design was actually flipped along its horizontal axis. I assume this is could have been another error-prone step in the design process.

Find the design files here

PCB traces PNG (left) and calculating process in Mods (right).

Milling the PCB

Gladly, I managed to avoid all of these pitfalls and quickly managed to finish the design in a short time frame. After exporting the files as PNGs (important: in exactly the same pixel aspect ratio!), I used the Community Edition of MIT's ModsProject to calculate the mill traces from the PNG source and convert them into the proprietary format of the Roland SRM-20 mill. The parameters used in the design and milling process were:

Trace mill: min. 1/64"
Outline mill: 1/32"
Minimal trace width: 0.35mm
Trace clearance: 0.4mm
Hole diameter: 1mm

Find the PCM milling files here

Milling during process (left) and the final milled outcome (right).

Soldering the PCB

Soldering the PCB was an interesting process due to the fact that the board had been intentionally designed in an inverted fashion: Through-holes were milled to receive female header pins to be soldered on the milled side directly on the contact points. This way, the visible side of the PCB is actually the 'back' of the board, showing only the substrate. The lower side (the milled side of the board), featured contact points for male header pins to be soldered directly on top without any through-holes. This way, the whole design was able to be executed with a single-side PCB, even though it features more than 100 headers (102 to be precise) on two sides of the board. Consequently, the soldering took almost two hours to complete. The outcome is nothing spectacular pr fancy, but the certainly our group is proud of.

Soldering during process (left) and the final soldered outcome, showcasing the male headers plugging into the Arduino (right).

Using the PCB

As simple the PCB is in its design, as effective it is in its use. Over the last two days, we managed to reduce the amount of circuitry on the breadboard almost completely and move everything to our Arduino shield. As mentioned above, this is not the most sophisticated design, but its incredibly effective and we were able to manufacture it in less than five hours – including design, milling and soldering.

The next evolutionary step is to redesign the board in order to offer integrated circuits for the potentiometers and buttons (including pull-up resistors) and offering each one of those as a JST or Grove connector style plug. This would effectively be comparable to a custom and enhanced Arduino Grove shield and offer a comparable plug-and-play functionality. For this step to be reached we need to settle on the exact number of connected potentiometers, buttons, pressure sensors and capacitive touch sensors. When or if we get to that point, this post will be updated.

Beginning to use the shield in order to phase out the breadboard circuitry.

Fabricating a Second Arduino Shield

In order to iterate in the proof of concept shown above, we tackled the challenge to introduce a new connector standard between our Arduino shield and the eight control units. After evaluating different solutions, among them MOLEX and Grove connectors, and weighing them agains their availability, price and open-source qualities, we settled on 3-pole 3,5mm standard headphone jacks. This allowed us to quickly purchase the needed quantity of components needed for the PCB fabrication, the controllers and long connecting wires. The drawback was that the sequential nature of the connector presents a constant risk of shorts. This is why the leading credo with this solution was: Never hot plug!

To integrate the connector standard into our project, we redesigned the Arduino shield used in Fab Challenge IV. After using the wrong pins on the eight surface mounted female 3,5mm headphone jacks, we redesigned the PCB a third time to allocate the correct connections. More impressions below.

Second PCB design including eight surface mounted female 3,5mm headphone jacks – unfortunately using the wrong pins...

Correcting the previous mistakes, using the right pins on the headphone jacks SMDs, shown here as black and white traces ready to be milled. Notice the minimal 0,4mm trace width.

Left: Due to the minimal trace width, we pulled off the copper traces off the substrate after soldering two male pins onto it. Right: Mitigating the problem via two cut jumper wires, which short the necessary traces at another point of the PCB.

Left: The final PCB after soldering the headphone jacks. Right: The central unit in its final 3D printed case including an acrylic cover.

Further Links

Output Devices

Input Devices

Week 10 & 13

Output Devices,
Input Devices

March 30 & April 20 2022

Fabricating an Arduino Uno Shield

Designing the PCB

Find the design files here

Milling the PCB

Find the PCM milling files here

Soldering the PCB

Using the PCB

Fabricating a Second Arduino Shield

Further Links

Output Devices

Input Devices

Week 10 & 13

Output Devices, Input Devices

March 30 & April 20 2022

Fabricating an Arduino Uno Shield

Designing the PCB

Find the design files here

Milling the PCB

Find the PCM milling files here

Soldering the PCB

Using the PCB

Fabricating a Second Arduino Shield

Further Links

Output Devices

Input Devices

Output Devices,
Input Devices