The Hidden Cost of Scaling Hardware: PCB Debugging and the Orbyt Ring’s 200-Unit Test

Building a prototype is hard - but scaling it to hundreds of units? That’s a different beast. In this post, we break down how we overcame critical PCB issues, antenna limitations, and manufacturing bottlenecks to take the Orbyt smart ring from lab experiment to real-world wearable. Whether you’re engineering a smart ring or scaling any small-form hardware product, this deep dive into PCB debugging, Bluetooth tuning, and firmware refinement will help you navigate the messy middle of product development.

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Why Scaling Hardware Isn’t Linear

Every hardware startup dreams of moving fast - from prototype to pilot to market. And in the early days, things often feel like they're going according to plan. At 10-20 units, hardware feels manageable. A bug shows up, you fix it, maybe even manually. But the moment you move past 100, the cracks begin to show - both literally and figuratively.

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The first twenty units of the Orbyt Ring worked beautifully - Stable Bluetooth connection, clean power profile, reliable data capture. It felt like we had cracked it.

But reality has a way of humbling you.

The moment we moved from 20 to 200 units, the game changed. We weren’t scaling problems - we were discovering new ones. It’s tempting to think that once your prototype works, the rest is just logistics. But the real complexity emerges at this scale. Issues that didn’t show up in earlier versions begin to surface. Tiny electrical miscalculations suddenly become major production blockers. That’s the hidden cost of scaling hardware: debugging doesn’t stop when your PCB boots up. It begins when you start building at volume.

Identifying the Bottlenecks

We started this phase by assembling a few smart rings using our existing v7 PCBs. On the surface, everything worked: the sensors collected data, the firmware ran smoothly, and the ring paired via Bluetooth. But beneath the surface, trouble was brewing.

Here’s what we noticed early:

• Bluetooth range was underwhelming: The antenna was functional, however range wasn’t ideal.

• Charging wasn’t intuitive: Our existing charger design was bulky and unintuitive for daily use.

• Sizing kit inefficiencies: Despite careful planning, many users weren’t able to find a perfect fit using our original sizing system.

More than anything, these initial builds forced us to go back to the PCB; because when scaling hardware, the PCB is your foundation. And any weakness in the foundation becomes amplified at volume.

The 1mm that Changed Everything

One of the most frustrating issues we faced came during programming. A few rings would intermittently fail to flash firmware. Others would complete programming but fail on reboot. After days of debugging, we discovered something so subtle it was easy to miss: a 1mm missing ground reference under a high-speed USB trace.

For those less familiar, a PCB (Printed Circuit Board) is made of stacked layers of copper and insulating material. Think of it like a tiny, vertical city. Signals move across these copper “roads”, and for high-speed signals like USB, the ground plane below acts like the structural foundation.

In our case, that 1mm gap in the ground plane completely disrupted the signal integrity. It’s like trying to drive over a bridge that suddenly has no support. The USB waveform distorted just enough to make programming unstable.

Our solution involved three steps:

• Restored the ground plane beneath the USB trace, stabilizing the signal.

• Reduced USB speed to ease rise times.

• Added decoupling capacitors, which act like electrical shock absorbers to maintain voltage stability during the programming burst.

Once these changes were implemented, programming became consistently reliable across test units. That tiny 1mm correction saved us countless hours of debugging - and gave us a newfound respect for PCB layout discipline at scale.

The Deep Sleep Dilemma

Once programming stabilized, another issue cropped up. A subset of rings would reboot and crash shortly after waking from deep sleep. The MCU (Microcontroller Unit) was acting erratically - sometimes skipping instructions, sometimes freezing.

The root cause turned out to be timing. After waking up from deep sleep, the ring needs time to allow its internal voltage to stabilize. In fact, any device at complete rest needs a few hundred microseconds to stabilize itself before it kicks back into action. But our code was resuming operations too quickly. The MCU was waking up before the electrical environment was ready - like starting a race before the track was fully built.

We fixed this with a firmware update that added a small delay between wake-up and code execution. This gave the system time to “warm up,” allowing voltages to stabilize before the MCU resumed work. It was a tiny change, but one that made the ring far more reliable during real-world usage.

The Antenna Challenge

Our initial PCB antenna layout faced inward, i.e., toward the metallic body of the ring. While this kept the ring compact, it crippled BLE (Bluetooth Low Energy) performance. Metal bodies reflect and absorb radio signals, and the coating used to protect the internal electronics made matters worse. Additionally, this configuration affected PCB bending, which is crucial for making the ring compact and comfortable to wear.

For a wearable like Orbyt, BLE range isn’t just a convenience; it’s crucial for syncing health data. So we went back to the drawing board. Here’s how we addressed the antenna issue:

• Reoriented the antenna to face outward, toward the visible portion of the ring.

• Redesigned the PCB curvature to improve structural integrity and antenna range.

To simulate how the ring would perform on actual hands, we used a hand phantom - an electromagnetic model that mimics the composition  of human skin. Testing this setup showed clear results: BLE range improved from a few centimeters to roughly 10 feet in open-air line of sight. In order to do this test, we had to make a cutout in the ring body and tap into the antenna trace directly for tuning the matching circuit.

Even after all these gains, our antenna partner believed there was room for further optimization. But the improvement was substantial enough to green-light our first 200-unit batch.

Debugging at Scale: What Yield Really Looks Like

With the new antenna layout and PCB corrections, we built the first 20 units from the 200-unit pilot batch. To our relief, 18 out of 20 worked flawlessly. We felt confident.

Then we assembled the remaining 180 units. Only 20 of them worked. It was a gut punch.

This was our first real encounter with yield unpredictability: a common but underdiscussed pain point in scaling hardware. The early success had lulled us into thinking the problems were solved. But variations in component tolerances, minute solder inconsistencies, and other invisible gremlins made mass production far more chaotic than expected.

We paused the build, reanalyzed the failed boards, and discovered inconsistencies in reflow profiles, solder masks, and PCB stack-ups. Even though the design was correct, repeatability across batches wasn't. That’s the thing about debugging at scale -  the problem isn’t always your schematic. It’s how consistently it can be produced and assembled.

We reworked our manufacturing QA process, updated vendor instructions, and added post-assembly testing rigs to catch failures earlier.

Refining the Ring: Beyond the PCB

While our primary focus was on the PCB, we didn’t ignore other aspects of product maturity. This phase also saw major improvements to the charging system and sizing kit.

The old charger was bulky and unintuitive. The new charger became a pocket-sized case that doubled as a travel holder. It could fully recharge the ring 10 times on a single charge; an essential feature for real-world users.

The sizing kit moved from a flexible band to PLA-based fixed-size rings. Instead of asking users to adjust a band, we sent them the three closest ring sizes based on a self-measurement quiz. It was faster, more accurate, and more eco-friendly.

These weren’t just cosmetic changes. They were essential for user experience. Charging and sizing are often overlooked in the prototyping phase, but they make or break the user journey at scale.

Final Thoughts: Scaling Is Debugging

Looking back, the journey from 20 to 200 rings wasn’t simply about production volume. It was about trust - trusting the hardware to behave the same way every time, at every scale.

That trust doesn’t come from design alone. It comes from systematic debugging, from testing not just what works, but why it fails. PCB debugging became the invisible hand guiding us through this process - from missed ground planes and wake-up crashes to BLE interference and yield variation.

For anyone building wearable hardware: don’t underestimate the transition from prototype to pilot batch. The hidden costs are not always financial. They’re in time, engineering patience, and the willingness to stare at a scope for hours to find a 1mm mistake. We’re still learning, still iterating. But the 200-unit test was a rite of passage. And now, every ring we build carries not just sensors and circuits - but the lessons that got us here.

In the world of wearables, performance isn’t just about the sensor spec sheet or form factor. It’s about repeatability, stability, and resilience at scale. Debugging the Orbyt Smart Ring taught us that. If you're a founder building hardware - don’t fear debugging. Design for it. Budget for it. Celebrate it. Because behind every refined product is a graveyard of lessons. And that’s where the magic happens.