This project began during one of my baseball classes, where my coach mentioned wanting a custom scoreboard. With my experience in IoT and a curiosity about electronics, I eagerly took on the challenge. What started as a simple idea turned into an incredible journey involving hands-on experimentation, multiple trips to local markets, and a lot of trial and error. Here’s the full story of how I built a functional Bluetooth-controlled scoreboard from scratch.
- Microcontroller: ESP32 (chosen for its Wi-Fi and Bluetooth capabilities)
- LED Control: TM1638 IC (initially recommended for multiplexing)
- Display: 8 seven-segment displays and 9 LEDs for visibility
- Power Supply: 24V, 12A switching power supply
- Additional Tools: Transistors, resistors, SMD-to-DIP converters, heat sinks, and aluminum for heat dissipation
The first steps were filled with research and sourcing. I started at Amjad Mall in Iran, asking shop owners about the components I’d need. After several conversations, I found a shopkeeper who guided me toward the TM1638 IC, which uses time multiplexing to control multiple segments and LEDs. I also picked up an ESP32 for Bluetooth and Wi-Fi support.
After gathering my components, I faced my first major hurdle: the TM1638 IC I had purchased was an SMD (Surface-Mount Device), which made it challenging to work with on a standard breadboard. I went to a local electronics shop in Karaj and finally found a helpful LED shop owner who explained how to manage the heat and power requirements for the high-intensity LEDs that would be visible outdoors. Armed with new knowledge, I purchased aluminum heat sinks and test LEDs.
To ensure sufficient brightness, I calculated the power requirements for the LEDs. With 49 segments needing 350mA each, I determined I’d need a power supply of at least 6V and 15A. I opted for a 24V, 12A power supply, confident it could handle the load. This setup also required a SMD-to-DIP converter to make the IC compatible with my breadboard.
One of my biggest challenges was figuring out how to control high-power LEDs with the ESP32, which outputs a maximum of 3V. Remembering a lesson on transistors from a university course, I decided to use them to manage the current. However, during testing, I miscalculated the current, causing one of the transistors to explode! After more research, I discovered that transistors have maximum current limits. I then experimented with stronger transistors, only to find that the ESP32’s 3V output wasn’t enough to activate them.
This was a point where I nearly gave up, but a senior at university suggested using a smaller transistor to control the larger one, creating a dual-transistor circuit. This solution worked, allowing me to control the LEDs with the ESP32’s limited output!
Once I had my circuit figured out, I decided to build on a perfboard instead of a custom PCB to save costs. This decision came with its own difficulties. I spent two weeks soldering LEDs, connecting segments, and ensuring each connection was solid with a multimeter. While tedious, this phase taught me the value of precision and patience in electronics.
As I powered the board, I noticed some LEDs burning out. Realizing I hadn’t accounted for the resistor wattage, I recalculated the resistance needed and came across a 9V regulator that simplified my circuit. With this, I could use 8-ohm, 1-watt resistors, ensuring each LED was properly protected without excessive heat.
After weeks of assembling, soldering, and troubleshooting, I powered on the scoreboard for the first time. Although some LEDs didn’t light up immediately, seeing it come to life was incredibly rewarding. I fixed minor bugs, adjusted connections, and secured each part, then programmed the ESP32 to control the scoreboard via Bluetooth.
- Android App: To make the scoreboard even more interactive, I plan to develop an Android app for Bluetooth control.
- Custom PCB: To improve reliability and reduce errors, I’d like to design a custom PCB in future iterations.
This project taught me resilience, problem-solving, and the intricacies of electronics. Each challenge brought new learning opportunities, from basic circuit design to complex power management. It’s a testament to the rewards of hands-on experimentation, and I’m excited to continue building and refining projects like this.
Thank you for reading about my journey, and feel free to reach out if you’re interested in similar IoT and electronics projects!