Posts on Charlie Howlett

Automating Backing Tracks

Sat, 22 Aug 2026 00:00:00 +0000

When rehearsing, alone or with others, I sometimes like to play along to backing tracks with a few of the original instrument parts removed. My hybrid drumming rig works well for this, but preparing the backing tracks can be a pain. Typically, I’d download an MP3 of the song, manually upload it to a stem-separation service, then re-export it in the TM-2’s expected format: stereo 44.1 kHz PCM WAV. This works, but preparing a couple of songs for a rehearsal can take quite a bit of time.

Managing My Homelab with Ansible

Tue, 18 Aug 2026 00:00:00 +0000

In previous posts, I described how I set up my repurposed laptop server and Raspberry Pi server rack. Together, they have grown into a useful little homelab.

The top-level topology is simple, but the deployed services and their configuration complicate things quickly.

It can be tricky to keep track of:

Automating LinkedIn Cross-Posting

Wed, 05 Aug 2026 00:00:00 +0000

I’ve been writing posts here for quite a while, and during that time the site has grown to cover a fairly wide mix of topics. I felt it would be nice to share that work with a larger audience, so I decided to implement a CI/CD pipeline for automatically cross-posting to LinkedIn.

Implementation

I originally considered using Zapier for this, but the free tier did not offer the functionality I needed, so I built a small publishing pipeline myself using GitHub Actions.

Jar Light Display

Tue, 28 Jul 2026 00:00:00 +0000

Almost every night I light a candle before going to bed as part of my nighttime routine, so I have heaps of leftover glass jars that seem too nice to throw away. Last weekend my girlfriend and I had the idea to turn one into a nice-looking enclosure for an interactive LED light project.

The first step was cleaning out the old wax and wick.

Next, we made a display that exactly fits the unique shape of the jar. We bought a strip of individually addressable LEDs, cut it into shorter sections, and wired them together into a flexible circular matrix.

Rebuilding a Small Garden

Fri, 10 Jul 2026 00:00:00 +0000

When I moved into my new flat earlier this year, I immediately noticed that the patio had not been looked after for a while. It had been left untidy and unclean, with unused furniture pushed around the space, weeds growing through the planters, green moss down the sides of the wood, and a surprising number of snails living in the corners. With summer coming up, I decided to turn it into somewhere I could actually sit outside and enjoy.

Mobile Dev Setup

Fri, 03 Jul 2026 00:00:00 +0000

I’ve always felt quite restless once I start working on a project. If I’m sitting in a park, on a train, or away from my desk with an idea in my head, I often want to make a quick change or keep a thread of work moving. But without my laptop I’ve always had to settle for doing something else. Still, I have always been curious about what options were available so years ago I looked into Termux, an app that provides a terminal on your phone. I wanted to try coding on the go, but writing productive code from such a small screen and keyboard felt impractical. However, when AI agents came along the idea started to seem much more realistic so I decide to try again.

Optimizing Hugo Image Loading Time

Wed, 24 Jun 2026 00:00:00 +0000

As I’ve added more posts to charliehowlett.co.uk, the site has gradually accumulated lots of screenshots, photos, and short animations. I usually upload whatever media files I have available without first optimising them for web, which can increase site size and negatively impact page load times. At first I thought to simply enable the img-bot GitHub action to automatically optimise images, but unfortunately the service’s free tier does not extend to private repositories. So I spent some time implementing my own automatic image optimisation process.

Reverse Engineering Roland TM-2

Fri, 19 Jun 2026 00:00:00 +0000

While building my compact hybrid drumming rig, I became very familiar with the Roland TM-2. The module has an enormous number of settings and even lets users save configurations to an SD card as .TM0 files. One day, I opened one of these files on my computer to see what was inside. I found mostly unreadable raw binary data, with a short string of plain English text at the top: the name of my save file. This led me to wonder whether I could reverse engineer the format and display all the information in a web-based user interface.

Monitoring My Homelab with Grafana

Wed, 17 Jun 2026 00:00:00 +0000

Once I had several processes running continuously in my homelab, I needed a single place to inspect what they were doing. Connecting to a machine via SSH and reading logs directly is useful, but hardly convenient, so I set up an observability platform. I use Grafana for querying and visualising logs, Loki for storing and querying logs, and Grafana Alloy for collecting and forwarding logs. The components run as Docker containers on a Raspberry Pi with an attached SSD for persistent storage.

Hugo Teletext

Mon, 15 Jun 2026 00:00:00 +0000

Earlier this year, I decided to revamp my personal site’s style and introduce a blog. I chose the static site generator Hugo because it keeps post content, written in raw Markdown, cleanly separated from site styling. Which should help reduce maintenance time and make cross-posting easier.

I originally planned to use a third-party Hugo theme, but after stumbling across the Teletext font at galax.xyz, I was inspired to design my own reusable teletext-inspired theme.

Git Auto Sync

Sun, 14 Jun 2026 00:00:00 +0000

After setting up my Raspberry Pi home lab, I deployed a small project onto one of the Pis and immediately wanted a cleaner method for continuous deployment. The app lived in a Git repository, and I wanted the running copy on the Pi to update automatically whenever the repo changed.

The obvious approach would have been a webhook: GitHub sends a request, a local service receives it, and the Pi pulls the latest code. I decided against that for security reasons. I did not want to expose a service on my home network just so GitHub could tell it that a commit had landed, and I did not want to build a tunnel or webhook receiver for something that could be solved more simply.

Monitoring Devices on My Home Network

Sat, 13 Jun 2026 00:00:00 +0000

My router gives me a basic view of the devices currently connected to my network, but it does not expose historical information. I started this project to fill that gap: a small Raspberry Pi service that scans the LAN, records which devices it sees, and shows that data in a dashboard.

Implementation

The service periodically runs arp-scan to discover devices on the local network, then stores the results in a database with both the current device state and a history of online/offline events. That split lets the system track when a device first appeared, when it was last seen, and how its presence changed across a day or week.

Building a Raspberry Pi Server Rack

Fri, 12 Jun 2026 00:00:00 +0000

I had three old Raspberry Pis and an SSD sitting unused in a cupboard, so I decided to turn them into a small cluster of home servers. I wanted the finished setup to be compact and tidy enough to live on a little shelf in my television stand, rather than becoming another loose collection of boards, cables, and power adapters tucked away in some cupboard.

For the chassis, I joined two 12-inch server rack trays using a pair of small rack-mounting posts. This was cheaper than buying a premade desktop rack and gave me a reusable foundation: if I later expand the cluster or move it into a larger rack, the trays and mounting hardware can become part of the new setup.

Repurposing a Laptop as a Home Server

Fri, 22 May 2026 00:00:00 +0000

I was recently given an old laptop that had been retired by my company. Despite no longer being needed for work, it still had quite capable hardware, so I decided to repurpose it as a compact, general-purpose home server rather than let it go unused.

Because the server will remain plugged in, I removed the battery to reduce unnecessary heat and avoid leaving an ageing battery permanently charging. I also removed the display, which improved airflow, made the machine easier to fit into tight spaces, and left the power button accessible without needing to open and close a lid. I saved the screen so it can be reused in a future project.

Repurposing a Drum Key

Wed, 13 May 2026 00:00:00 +0000

A drum key is a small tool used to turn the square-headed tension rods that hold a drum head in place and control its tuning. Using a drum key by hand works well for occasional adjustments, but an attachable drill bit can be very handy for more frequent use. However, commercial drum key drill bits seemed a little pricey for such a simple tool, so I decided to try making one myself.

GitHub Action to Automate Screenshots

Wed, 06 May 2026 00:00:00 +0000

Screenshots can make project documentation much clearer, but they quickly become misleading when they fall out of date. I built update-screenshots-action to automate that maintenance: capture a web page, save the image in the repository, and update a known section of a Markdown file.

Implementation

The action takes a URL, opens it in Chromium through Playwright, and captures either a PNG or an animated GIF at a repository-relative path. It then rewrites a marked block in a Markdown file so the reference remains in sync with the generated asset. Optional commit-and-push support allows the action to run on a schedule or after changes to a site without requiring additional workflow steps. Even within that narrow scope, running reliably in CI required handling several operational details. Navigation is retried while local preview servers start, and commits are only created when one of the managed files has actually changed.

Upgrading a Seiko DM-20 Audio Jack

Sun, 12 Apr 2026 00:00:00 +0000

Recently, I found a Seiko DM-20 digital metronome in a nearby second-hand electronics shop. I really like its compact, thin design and retro appearance, and thought it would be useful during band rehearsals where I often have to bring a much larger metronome.

The only problem was its 2.5mm headphone socket. Most modern headphones and audio cables use a 3.5mm connector, and although an adapter would have worked, it would also have added another small component that could be lost or fail during a rehearsal. I decided to replace the socket so the metronome could connect directly to the equipment I already use.

Framing Six Years at MindLink

Fri, 04 Jul 2025 00:00:00 +0000

For software engineers, the ethereal nature of our work often means we’re left without many physical reminders that it ever happened. That can make it surprisingly hard to look back and celebrate what we’ve actually done, especially after constantly moving from one project to the next. I’ve certainly felt that myself, so I’ve made a point of holding on to a few keepsakes over the years. After finding several of them during a recent spring clean, I decided to turn them into a display for my office shelf.

Building a Compact Hybrid Drumming Rig

Sat, 03 May 2025 00:00:00 +0000

As a drummer in central London, I spend a lot of time going to different practice rooms and using their house kits. The convenience is great, but the kits are unpredictable, and some can sound less than ideal. Even quickly retuning every shell can take up a significant part of a two-hour practice slot. I needed a way to improve my sound without dragging a full drum kit across the city.

Building an Arduino Robot Car in a Day

Wed, 12 Jun 2024 00:00:00 +0000

I set myself a small challenge: build a working Arduino robot car in a single day, using only electronics parts I already had around the flat.

I decided to build it because I had found a TB6612FNG motor driver lying around, along with an Arduino Mini, a battery pack, and a couple of small wheels with DC motors. For the body, I used a little wooden board I had spare and fixed the motors and other parts to it with some metal joinery pieces.

Arduino LoRa Monitoring System

Tue, 11 Jan 2022 00:00:00 +0000

I rent a small drumming practice space that I share with several other musicians on a timetable basis. I built this monitoring system to understand how often people were using their booked time slots and how the room’s environmental conditions changed over time. Since the space has no Wi-Fi and unreliable mains power, the project became an interesting challenge involving low-power hardware, long-range radio communication, and remote data collection.

Sensor node

The sensing node is built around a 3.3V Arduino Pro Mini with sensors for PIR motion, humidity, temperature, and ambient light. Every ten minutes, it wakes up, collects readings, packs them into a small JSON payload, transmits the result by radio, and returns to sleep. I spent a significant amount of time reducing its power consumption so the device could run for roughly six months from three AA batteries. For this project, reliable long-term monitoring mattered more than collecting readings more frequently.

Llama Bot

Sat, 01 Jan 2022 00:00:00 +0000

This project started with a burst stress toy llama that seemed too good to throw away. I decided to give it a second life as a singing, dancing robot, which turned a cute toy into a compact embedded engineering project involving electronics, power, motion, and control logic.

Implementation

The electronics were built around an Adafruit Feather HUZZAH ESP8266, with a servo for movement, a buzzer for playing songs, and a rechargeable LiPo battery connected to the board’s micro-USB charging port. I also added an on/off switch by grounding the ESP8266 enable pin, allowing the toy to draw effectively no current while switched off instead of slowly draining the battery. Inside the llama, a structure made from cardboard, copper wire, and hot glue held the components in place and made the damaged toy sturdy enough to survive repeated movement.

Automating Lights with a Raspberry Pi

Thu, 02 Sep 2021 00:00:00 +0000

Pi Lights was a fairly simple idea and my first exploration into DIY home automation: measure the ambient light level throughout the day using a Raspberry Pi, then switch Wi-Fi lights on or off automatically.

Implementation

The system polls several light-dependent resistors and averages their readings before deciding whether to switch the lights. Using multiple sensors and rate-limiting changes made the automation less sensitive to brief shadows or sudden changes in brightness. A dedicated light-sensing Raspberry Pi HAT would have been more accurate, but I wanted to see if I could build a first pass using components I already had lying around. I ran the software as a Linux service so it would start automatically and continue working in the background without needing any attention.

Building an Earthen Oven in Tanzania

Sun, 01 Sep 2019 00:00:00 +0000

In 2019 I spent three months volunteering with ICS in rural Tanzania, providing entrepreneurial education and funding to a group of villagers. During this time the families who volunteered to host my team generously cooked for us every night, and I wanted to return the favour by making them some food from the UK.

However, I quickly realised that a lot of UK food assumes access to an oven, which no one in the village had. Fortunately, around this time i came across the concept of earthen ovens and saw how simply they could be made from local materials, and decided to try building one myself.

Anti-Lock Braking System

Sun, 17 Mar 2019 00:00:00 +0000

Overview

My final year at university was primarily focused on my dissertation, for which I chose to implement and evaluate an anti-lock braking system. The idea was suggested to me by a professor who noted that an accurate, open-source ABS model would aid his research. To achieve this, I based the ABS control loop on a Bosch algorithm described in engineering literature and ran simulations using the open-source software “Speed Dreams 2”, which features advanced vehicle physics.

Procedurally Generated Clouds

Mon, 04 Mar 2019 00:00:00 +0000

Fullscreen

While at university I first started thinking about building a personal site, and from the beginning I knew I wanted it to feel unique and a little artistic. So in 2019 I built the procedurally generated p5.js sketch above and deployed it as a simple single-page app on Netlify, along with some basic contact information.

Each cloud is created algorithmically rather than relying on static images, which means every run produces a slightly different scene. I later expanded the sketch with mountains, a moon, stars, and a dark/light switcher to make the whole scene feel more complete.

University Game Development

Tue, 19 Feb 2019 00:00:00 +0000

Universe City was born from a group software project I worked on during my Computer Science degree at the University of York. Our brief was to create a game in Unity, and our team decided to build a turn-based strategy game inspired by Risk, replacing countries and armies with a deliberately light-hearted version of university life.

Players represented University of York colleges such as Halifax and Derwent, competing to capture sectors across the map and eliminate the other factions. The game supported between two and four human players. Alongside the main strategy systems, we built menus, resource displays, victory detection, and a Vice-Chancellor dressup minigame.

Raspberry Pi Digital Lock

Fri, 02 Nov 2018 00:00:00 +0000

This first-year group project started with a simple brief: build a keypad-controlled digital lock using a Raspberry Pi. It was a small project, but a very rewarding one, and it introduced me to some great people. Ultimately, our project was chosen by the lecturer to be demonstrated at subsequent university open days.

The main constraint was that we were not allowed to rely on interrupt-driven input for the membrane keypad. Instead, we had to detect key presses by polling the Pi’s pins and working through the keypad matrix ourselves. On top of the basic four-digit passcode entry, we added status LEDs for correct and incorrect codes, a short delay after failed attempts to make brute forcing less practical, and a text-based interface for changing settings after the user had gained access. We also wrote software to attack our own system by generating electrical signals that mimicked key presses.

Decoding a Pen

Tue, 23 Oct 2018 00:00:00 +0000

I recently came across a HMGCC recruitment pen with a curious message printed along the side. It seemed to be a small hexadecimal puzzle, which piqued my curiosity enough to see if I could decode it.

After manually transcribing the hexadecimal values from the pen, I first played around in CyberChef to get a feel for how the message might be encoded. Once I had a likely approach, I wrote a short Python script to put the decoding steps somewhere concrete:

Go-playing Bot

Fri, 17 Mar 2017 00:00:00 +0000

The Go bot interface, including the board and move history

Monte Carlo Go Bot

One of the earliest substantial software projects I built was a Go-playing bot for my Extended Project Qualification in sixth form. I had initially planned to build a chess bot, but once I realised how well simple brute-force algorithms could perform in chess, I decided to take on a more challenging problem. I turned my attention to Go because, at the time, it was one of the few classical board games in which human players still regularly beat machines.