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PCB & Hardware Design

pmolver — Sat, 24 Jan 2026 14:12:34 +0000

PCB & Hardware Design

In University

University gave the a wide range of experiences in PCB and Hardware design. Several projects required custom PCBs and KiCad was the tool of choice in early years for licensing reasons. Many of my early projects were simple Arduino hats with only a couple features such as an ADC on board.

Personal Project

In later years, in Embedded Systems 2 I got to create the PCB which would control the racer body, and this included placing and soldering the individual components on the PCB.

In my free time, I worked on a project called GrowSimple, this device was a simple watering device but due to feature creep, it’s resulted in a device that does more than simply turn on and off a 12V water pump. This has had several challenges, such as how would I assemble and enclose the PCB? How can I create something somewhat modular as different micro gardens require different features, and how do I provide value for a product that will be expensive due to it’s low volume nature?

Features and Challenges

The Grow Simple project was interesting to work on due to the various challenges I had to overcome;

User Control – The beauty of the ESP32 is the cost and feature set, having BLE available meant I could create a web based user interface to interact with the device, without any server cost, or app store fees. The problem is feature creep and development time to implement all the features required such as file transfer and OTA updates.

Device Status – I picked a side mount RGB component and have a small acrylic tube that sits in a custom 3d printed wire grommet, this acts as a light tunnel and allows for the device status to be seen by the user while ensuring that the water tightness of the device remains.

External Modules – The D-C pins at the top of the PCB are for data and clock, I use I2C to allow for devices to be plugged into the device, and the device can scan for connected devices on boot and then display the relevant BLE characteristics. This was challenging as I was not able to find a low cost, consumer friendly plug for this application. I instead used a 4 pole 2.5mm audio jack as this is intuitive and easy to source for a low cost.

Power and PCB – The small enclosure I picked meant that I had limited space to work with but I still managed to implement a buck converter to 5V for external modules, and another 3V3 LDO regulator for the ESP32. The 5V module power was picked to allow for more variety of external modules, more power availability to them, and a better Signal-Noise ratio.

Industry Experience

Working at OnFarm Data gave me many opportunities to both work with different software, and learn from the best. Working here I learnt how to better implement power planes, share and discuss ideas for the hardware I was developing, testing and test strategies, and document both the PCB details and assembly instructions.

Pictured is a small project I worked on that was essentially a solar charger for a Li-ion 18650 battery which was common in our products. This allowed for two different panel types to be selected for the MPPT and charging chip.

In addition to smaller modules just mentioned, I also worked on large projects that were core to the company focus such as an exclusion Input/Output PCB. This project featured an Input IO expansion module, and a second for output, and using I2C and an I2C range extension module, a series of up to 4 PCB could be placed on a pivot controlled by a single micro controller allowing for 64 additional inputs and outputs available to the micro controller.

This PCB had to allow for 12V or 24V input, and the input logic had to account for 2 possible logic levels being returned. Additionally, due to the 16 channels on the PCB, this was a tight design that tested my routing and component placement abilities.

For safety, each output had a surface mount resettable fuse to ensure that in the case where the output wire was damaged, that the rest of the installation was capable of performing it’s job until the cable was fixed. There was also reverse polarity protection and an RGB led to indicate the address of the PCB to allow for easy confirmation that the DIP switch was correct.

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STM32 Embedded Development

pmolver — Thu, 22 Jan 2026 09:27:04 +0000

STM32 Embedded Development

Development during internship

During my internship at OnFarm Data, I worked on integrating the Swarm satellite communication module into the existing data-logger. This was to provide a method of communication in areas where there was no cell coverage, or internet available.

In order to integrate the swarm module, I had to modify the software interface which selected the communication method, from this point, I would have to create the standard interface functions such as ‘send’, in addition to swarm specific communication functions.

Due to the small packet size and message quotas, I also developed a packing function where the packet could contain multiple logs. This had to be flexible as the log size was dynamic based on the sensors attached.

Challenges

The hardest part about developing this software was dealing with debugging brownouts and not being able to trigger satellite transmissions whilst working in the office. This was resolved with hardware modifications.

It was also challenging working within a large project for the first time where features required changes to multiple systems within the code and having to understand the logic flow.

After my internship

Whilst embedded development duties slowed after my internship, I still had the opportunity to occasionally work on embedded software. One of the features I implemented was the SD card logger. This code essentially hooked into the console output code and wrote the console message to an SD card. It also included the timestamp into the folder structure, filename, and prepended to the new text. This allowed for console output to be pinpointed and allowed for additional debug information for instances where a console couldn’t be used.

Challenges

The SD card filename wasn’t long enough to include the entire length of the timestamp, so I had to remove the least significant digits in the file name. Additionally, I had to solve how to figure out the current time, and roll over the file when a new day occured.

Creating drivers for hardware projects

Later in my tenure I used embedded development for creating drivers for the hardware I was developing.

In the exclusion project I coded the ability to set and receive states of the IO expander. Additionally, I created similar software to collect data from a Davis weather station which used a mix of I2C, ADC, and pulses to capture weather data.

In the case of the exclusion project, the a custom version of the code was made to set the STM32 to output a sequence of output states to the exclusion hardware which could be used to test devices during manufacture.

Challenges

When working with the exclusion project, a pin of the I2C connector was dedicated for indicating when a state change had occurred. However, writing to the device would induct into this wire, triggering the interrupt to cause another read event.

This information was used to inform my senior to implement a RC filter onto the main control board to prevent communication based induction from falsely triggering the interrupt pin.

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Aquaflex Manufacturing

pmolver — Thu, 22 Jan 2026 09:18:19 +0000

Aquaflex Manufacturing

What is Aquaflex?

Aquaflex is a novel solution for capturing the soil moisture for use in Agriculture. Multiple can be used to provide additional information about how deep the water is. Unlike the majority of sensors on the market which are cylindrical and installed into a deep round hole, the Aquaflex is installed into a trench.

The advantages of the Aquaflex are that there is more soil measured and therefore you are more likely to get a realistic representation in your recorded data.

Manufacturing Excellence

When tasked with manufacturing the Aquaflex, I was given an outdated procedure, and a blank slate for how I set up the work space. Whilst I was given a manufacturing document, it detailed the steps, but now how best to perform them.

PCB testing using sound

The Aquaflex test jig is an old piece of software and hardware. It uses a 12 position dial with each dial performing another test. Some tests were seconds long, whilst some were up to 30 seconds long. Using Python I created a simple beeper script that would await the pop up messages that the test software generated, by using short and long beeps to indicate different testing stages I could perform tests without looking. This method required less attention to the pop ups that showed on the screen, and reduced fatigue when PCB testing, and increasing speed.

Cutting 10 meter cables made quick.

The 10 meter cable is a digital signal cable to connect the sensor PCB to the datalogger. Drums came in 100M lengths and length didn’t have to be exact. By reframing the problem as trying to get 10 equal lengths from the data cable I could significantly reduce the amount of physical labor required, and time required. I did this by 3D printing a span of 10 U shaped groves that could be glued to the original cable drum. By wrapping the cable around the cable drum, and using the grooves to count the wraps I could simply spin the drum to a certain point, cut, release tension, and zip tie. Another advantage is that by wrapping the cable around a drum the cable was already coiled up which is the state it needed to be in for final packaging.

3D printed solutions

I leveraged my ability to create 3d models heavily in the manufacture process.

• Slots and guides for the cutting of the sensor cable. This had to be as exact as possible and the slots and guides ensured the cable was as straight as possible.

• Potting jig, the potting jig had to be reconstructed but I was able to create an O shaped slot for potting cups to sit into and a router cut guide. I could use a router to rough cut the holes needed, and then glue in place the slots to perfectly seat the potting cups.

• The Aquaflex has software to measure the sensor in certain states and from this information it can create a trimming profile. I found that the orientation of the sensor in the water bath could dramatically effect the sensor readings. By creating a U shaped slot that would sit in the water bath, I was able to fix the sensor block in place for all sensors and create more accurate readings for the trimming process.

Recording results, reducing recalls

I improved the process of the final quality assurance step. By recording the sensor in a variety of states I was able to enter this into a google spreadsheet which allowed us to track the average performance of each individual sensor, it’s serial number, as well as identify outliers. This information is key as it acts as another resource when trying to diagnose data issues as this spreadsheet can referenced against a customers serial number. It also allowed for the creation of metrics to evaluate batch results between batches.

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Stainless Steel Enclosure

pmolver — Thu, 22 Jan 2026 09:17:08 +0000

S.S enclosure for PCB

The Task

This enclosure is designed to be mounted on a variety of different pipe sizes, providing a water proof solution to housing both power supplies and PCBs to be mounted onto an irrigation pivot for individual dripper control.

Considerations

– Finding box dimensions that would best accommodate PCB’s and power supplies with dimensions that could not be changed.

– Ensuring that there were enough cable for a variety of configurations, and that they were positioned with space for tool access.

– Branding, how was the device going to carry the company image?

– How would it mount to the pipes? Was the bracket strong enough? Could it clamp without rotation in high winds?

– Assembly, how were the contents to be installed and assembled, and finally the complete unit installed?

The manufacturer of this unit was a specialist box manufacturer which helped simplify the design as I didn’t have to design the door. However, depth turned out to be a key dimension. DIN mounted power supplies were narrow but very tall. Additionally, height needed careful consideration for cable entry as routing over 30 DC pairs into the box required space for the cables to flex.

Features

The enclosure features two holes on top, weather sealed and required for the solar panel and GPS antenna.

On the bottom are cut outs for large glands for the many DC pairs required, and smaller glands for power, antenna and communications wiring.

Inside are 4 posts allowing for the use of a gear try, allowing for assembly and testing outside of the box. Once all the gear is assembled on the tray, it can be tested before final installation.

The Result

With careful planning, this design ended up as a robust piece of gear that could house a variety of components and be mounted anywhere on the irrigation pivot. Correct manufacturing procedures resulted in complete water tightness even with cut outs at the top of the box. The stainless steel material ensures that the gear inside is protected through all seasons and for many years to come.

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