# Orbigator Dev Log: From Simulation to Reality
It’s been a while since the last update, and the Orbigator has evolved from a collection of parts and Python scripts into a fully integrated, silent, and precise satellite tracking machine.
Here is the story of how we got here.
## 1. The Hardware Pivot: Steppers vs. Smart Servos
We started where most builds start: **Stepper Motors**. They are cheap and ubiquitous. But for a device meant to sit on a desk and track the ISS silently 24/7, they had drawbacks. They vibrate, they make noise (“singing”), and crucially, they are **open-loop**—if the arm gets bumped, the system loses its place and stays lost.
We pivoted to **Dynamixel XL330** smart servos.
* **Silence**: They are virtually silent at tracking speeds.
* **Closed-Loop**: They know their absolute position. If you push the arm, it fights back (torque!).
* **Cabling**: They daisy-chain on a single bus, drastically reducing the rat’s nest of wires.
## 2. The Brain Transplant: MicroPython on Pico 2W
We moved the logic from a desktop PC to the **Raspberry Pi Pico 2W**. This brought its own set of challenges, primarily **Floating Point Precision**.
Standard SGP4 libraries assume full 64-bit float precision. On a microcontroller payload, 32-bit floats aren’t precise enough to handle Julian Dates (numbers like `2460678.12345`) while keeping second-level accuracy. Our initial tracks were off by thousands of kilometers!
**The Fix**: We refactored the satellite math to use **Integer Unix Timestamps** for the heavy lifting, only converting to small relative offsets when necessary. We verified this against NASA’s own trackers, bringing our error down to a negligible **~50km** (on a global scale).
## 3. The Interface: Web & OLED
A tracker isn’t fun if you don’t know *what* it’s tracking.
* **OLED HUD**: We added a tiny 128×64 display on the base for immediate stats: Latitude, Longitude, and current satellite name.
* **Web Dashboard**: Since the Pico 2W has WiFi, we built a hosted React dashboard. You can connect to the Orbigator from your phone to see a 3D visualization, change the tracked satellite (ISS, Hubble, Tiangong), and tweak settings live.
## 4. Tuning the Mechanics
The Arguement of Vehicle (AoV) arm (the part that looks like a closed pair of scissors) completes one revolution per orbit. It is counterweighted to balance the system and alievate motor wear. Physics caught up with us. Adding the AoV assembly—complete with magnets and pennies for counterweights—introduced a pendulum effect. The motor would “wobble” as it tried to hold position.
We wrote a custom auto-tuning script (`tune_wobble.py`) to cycle through PID profiles. We landed on a stiff-but-smooth profile (`P=600, D=0`) and capped the speed. Now, it glides.
## 5. What’s Next?
The mess of wires you see in the photos is “development aesthetic.” It works, but it’s fragile.
The next phase is purely hardware. I’m teaming up with **Anool** and **Kevin** to design a custom **Orbigator Control Board** that integrates the Pico, the RTC (Real Time Clock), and the motor drivers into a single, clean PCB.
The code is committed, the math is integer-perfect, and the motor is zeroed. Onward to proper PCBs!
Open Source Repo: https://github.com/wyolum/orbigator/
