Being away at sea for months makes even simple things like "where is he now?" hard to answer. Reddit user mrnks13, who is about to spend nearly four months on a ship from France to Singapore, built his girlfriend a small answer to that question. It is a wooden birdhouse with an ESP32 inside, a three-colour e-paper map that shows where his ship is, and a thermal printer on the roof that prints her a note every day. A plush raccoon peers out of the entrance hole.
How it works
The build uses a NodeMCU ESP32, a Waveshare 4.2 inch three-colour e-paper display and a generic TTL thermal printer from AliExpress, all wired with Wago connectors and powered from an external 5 V, 5 A supply. The ESP32 polls VesselAPI over Wi-Fi for the ship's position and draws it on a custom map. The maker made that map in QGIS, the free GIS tool used by cartographers, cropped it to the route between France and Singapore, and scaled it down in GIMP to suit the 4.2 inch screen. E-paper is a good fit here because the image stays visible without power between updates, and a ship's position only changes slowly.
The thermal printer handles the personal side. Each day it prints the current port of call, the time offset between the ship and home, and a countdown to his return, along with automated and personal messages. Instructions on the back explain how to set up the Wi-Fi and renew the VesselAPI key, which is only valid for 90 days.
The LTE lesson
The first plan used a LilyGO T-Call A7670E so the tracker would work over LTE without home Wi-Fi. Once the modem was active, the e-paper showed only red static. The maker replaced the screen, then tried soldering capacitors onto it, before finally measuring the supply. Every time the modem tried to register on the network, the rail dropped from 5 V to between 0.2 and 3.5 V. Cellular modems draw short current bursts of up to 2 A while transmitting, so a weak supply or thin wiring can bring the rest of the board down with it. With the deadline close, he moved to a standard ESP32 on Wi-Fi and the device has run stably since.
Our take
This is a beginner project in the best sense. The maker is new to microcontrollers and used Schematik and Gemini for help, but the finished device solves a real problem, and the debugging story is the most useful part: measure the supply first. He has offered to publish the code and parts list. To build something similar, see our guides on using a thermal printer with the ESP32 and driving an e-paper display.
Image credit: mrnks13 / Reddit, cropped and resized.
About the author: Aswinth Raj is an electronics engineer and the editor of CircuitDigest, where he has published more than 150 hands-on projects and tutorials across Arduino, PIC, ESP32, Raspberry Pi and EV battery systems. He selects the stories on this page for what engineers and makers can actually learn or build from. Connect on LinkedIn
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