A8 - Electronics Design

Brief

Use an EDA tool to design a development board to interact and communicate with an embedded microcontroller

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https://fabacademy.org/2024/labs/lakemac/week8-group/

All of the tests in the group assignmen are common tests we do in Uni assignments and ones I do for personal projects, 'designing' these tests were relatively easy. But one issue was finding a good way to place the multimeter and oscilloscope probes - using test points would have been a great design inclusion.

Designing a node

My project requires many 'nodes', a device that can get all of the sensor values then turn off. On the node will be soil moisture sensors, and I2C port for more sensors and a nano power timer.

I already have a substantial amount of experience in KiCAD an open source and easy EDA software.

Schematic

On the left are all of the inputs, 4x soil moisture sensors connected to analog pins on the ESP32-S3 Xiao, then an I2C connector for Atmospheric, Light or any other I2C sensors we might want to use.

The Xiao has an additional 2 pads underneath we can use to bypass the onboard diode from USB - isntead using the MOSFET, keeping power consuption lower, a dedicated connector will be made for this.

Then power, we plug the power timers output into the Xiao's battery connector. And can measure the voltage using a high impedance voltage divider.

Node schematic

PCB layout

Footprints were created from datasheets/dimension drawings where necessary.

I havent had a lot of experience designing boards on a single layer and wasnt keen on soldering headers from the top side, instead of underneath.

So I designed the board on the backside and before printing the gerbers, flipping it before milling, now components could go on the top side.

Node layout

Milling

The same process was followed from A4 - PCB Milling, though one suggestion for Mods would be to add a flip option, and adding all 3 files to their respective flows.

... After generating the gcode, I failed to realise there was white-space in each of the images, so the board outline did not match the zero point of the mill.

xxx TODO IMAGE FAILED PCB MILL

I remilled it with an approximated offset and got the desired result.

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PCB Fabrication House

I also got this board produced at PCBgogo, the whole process was simple, quick and cheap.

Both results turned out very well and produced working boards (albiet with different configurations).

xxx TODO IMAGE of blank PCB

xxx TODO IMAGE of side by side soldered

FILES

DOWNLOAD LINKS HERE - Zip with KiCAD project, SVG's, rml and gerbers