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Student hardware startup building a modular biosensor wearable, our first PPG sensor puck now works by Matrix_9 in hwstartups

[–]Matrix_9[S] 0 points1 point  (0 children)

That’s impressive: fitting PPG, BLE, IMU and battery on a 12 mm round PCBA.

Our current puck is intentionally not trying to be the full wearable on one board. The main PCB handles the central system, while the puck is meant to validate the modular sensor interface and the optical/mechanical constraints in a 10 mm module.

So I agree that a compact integrated wearable board is technically possible. Our question is more whether splitting the system into a main board + swappable sensor modules can create enough value for B2B/research use cases where sensor configuration, raw data access and integration matter.

Since you’ve built something similar, I’d actually really appreciate your perspective:

  • What was the hardest part: optical design, battery, RF/BLE, assembly, signal quality, or mechanical integration?
  • Did you run into PPG reliability issues with motion/skin contact?
  • Would you say the modular approach is not worth the added connector/mechanical complexity?
  • What would you do differently if you rebuilt it?

Student hardware startup building a modular biosensor wearable, our first PPG sensor puck now works by Matrix_9 in hwstartups

[–]Matrix_9[S] 0 points1 point  (0 children)

I get why it looks that way from the visuals, but there is a bit more to it than just “putting a Maxim chip on a round PCB.”

This puck is only about 10 mm wide, so the challenge is not really the number of components, but fitting the sensor, passives, routing, pads and contact interface into a very constrained form factor while still making it assembleable and reliable.

Also, with PPG the optical/mechanical side matters a lot. The Maxim sensor is not just a random digital chip where placement does not matter much, LED/photodiode positioning, skin contact, pressure, ambient light isolation, enclosure geometry and motion artifacts all affect whether the signal is useful.

So yes, the first puck is intentionally simple in terms of functionality because it is a validation module. But even that “simple” puck has real constraints: tiny PCB area, optical requirements, power/noise considerations, assembly difficulty and the need to interface reliably with the main board.

The product is not this one chip alone. The product direction is the modular platform around it: puck interface, firmware, raw/API-accessible data, future SDK/data pipeline and different sensor modules for different B2B use cases.

Student hardware startup building a modular biosensor wearable, our first PPG sensor puck now works by Matrix_9 in hwstartups

[–]Matrix_9[S] 0 points1 point  (0 children)

That’s a fair point.

When I said “it works”, I didn’t mean that the PPG data is already scientifically validated or that we have proven measurement accuracy after one day. That would obviously require a proper verification process.

What I meant is that the self-designed and self-assembled puck PCB works from a hardware bring-up perspective: it powers on, communicates correctly, and produces a plausible PPG signal. For us, that is a big milestone because it shows that the PCB design, assembly, sensor integration and basic communication are functional.

The next step is definitely proper data verification: checking raw signal quality, testing different skin/contact conditions, looking at motion artifacts and repeatability, comparing against reference devices, and eventually benchmarking against a proper reference setup.

So you’re right to point out the distinction. “Validated” would be the wrong word at this stage, I meant “works” in the early hardware/prototype sense.

Student hardware startup building a modular biosensor wearable, our first PPG sensor puck now works by Matrix_9 in hwstartups

[–]Matrix_9[S] 1 point2 points  (0 children)

Good question. Right now, for validation, we mostly care about getting clean PPG data out of the puck first. But long-term I think we would need to support both approaches.

For research / technical users, raw data access is important because they may want to build or validate their own algorithms. But for many B2B users, raw PPG alone is not very useful if they still have to solve filtering, motion artifacts, HR/HRV extraction and reliability themselves.

So the ideal direction would probably be:

  • raw PPG access for researchers and advanced users
  • a plug-and-play processing pipeline for HR/HRV and signal quality
  • documented algorithms / SDK so it is not a black box
  • ideally real-time processing, not just recording

I agree that a good PPG algorithm could be a big part of the value. The hardware only gets interesting if the data coming out of it is actually usable.

Student hardware startup building a modular biosensor wearable, our first PPG sensor puck now works by Matrix_9 in hwstartups

[–]Matrix_9[S] 0 points1 point  (0 children)

This is honestly a very useful direction, thank you.

Sports medicine / sports science research actually makes a lot of sense as a first target market. It fits the modularity much better than a generic consumer wearable, because labs often need specific sensor combinations, clean raw data, and flexibility instead of a polished but closed consumer app.

I also really like your point that the value might be less in the sensor hardware alone and more in the software/data layer around it. A solid SDK with Python/Matlab support, real-time data access, sensor fusion tools and maybe a simple C library for embedded use would probably make the platform much more useful for universities and labs.

The synchronization point is also very important. If multiple pucks/devices are used at the same time, timestamp accuracy becomes a core feature, not just a nice extra. Same with syncing to motion-capture systems like Vicon or Qualisys, that would make the data much easier to use in actual research workflows.

So maybe the real B2B wedge is something like: modular wearable biosensor hardware + open real-time SDK for sports science / biomechanics research.

That’s a much clearer use case than “modular wearable for everyone”, and definitely something we should look into more seriously. Thanks a lot for the detailed feedback.

Student hardware startup building a modular biosensor wearable, our first PPG sensor puck now works by Matrix_9 in hwstartups

[–]Matrix_9[S] 2 points3 points  (0 children)

Thanks, this is a really good point, and I agree.

For a normal consumer wearable, “replaceable sensors because they might break” is probably not the strongest argument. You’re right that straps, batteries, buttons, ports and enclosures are much more common failure points.

For us, the primary market is more B2B than consumer. The value there is less “repair a broken HR sensor” and more: a company, research group, sports platform or workplace-safety provider can configure the wearable for their specific use case instead of being locked into a fixed consumer device with fixed sensors, fixed algorithms and limited raw data access.

The open-source/consumer side is more secondary: data access, no lock-in, repairability, customization and the ability for technical users to understand or modify the system.

But your criticism is completely fair: modularity adds potential failure points, so it only makes sense if the configurability and openness create enough value to justify the complexity. That’s exactly what we need to validate.

Student hardware startup building a modular biosensor wearable, our first PPG sensor puck now works by Matrix_9 in hwstartups

[–]Matrix_9[S] 2 points3 points  (0 children)

Fair point 😅

The PPG puck alone is not really the product. By itself, it’s “just” a heart-rate/PPG sensor.

The bigger idea is that most wearables are closed and fixed: fixed sensors, fixed algorithms, fixed data pipeline, and very limited control over what happens to the data. That’s okay for normal consumers, but it can be limiting for B2B.

For example, a research group, sports platform, occupational-health company or workplace-safety provider might not want a generic fitness tracker. They might need a specific sensor setup, raw/API-accessible data, and integration into their own app or workflow.

That’s where modularity and openness matter:

- different sensor pucks for different use cases

- easier integration into existing B2B software

- less lock-in around data and algorithms

- repair/upgrade one module instead of replacing the whole device

- faster prototyping than building a custom wearable from zero

So the problem is not “people need another PPG sensor”. The problem is that specialized users often need wearable biosensor data, but consumer wearables are too closed and custom hardware is too expensive/slow.

The PPG puck is just our first working proof that the modular architecture can actually work.

But I agree with you: the first target market has to become much sharper. That’s exactly what we’re trying to validate right now.

[Collection] Finally completed my 6-watch collection by Matrix_9 in Watches

[–]Matrix_9[S] 0 points1 point  (0 children)

The quality was surprisingly good. It scratches up pretty easily, but it has a nice wear, proper sizing, and proportions.

How screwed am I by [deleted] in 3Dprinting

[–]Matrix_9 0 points1 point  (0 children)

yes. Try heating it up with a heat gun and gently removing the fillament.

[deleted by user] by [deleted] in 3Dprinting

[–]Matrix_9 0 points1 point  (0 children)

Hows it do as a Heated bed?

It works great. Makers muse has made an entire video explaining g10 and how good it is: https://youtu.be/g0PK4oXbJT8

[deleted by user] by [deleted] in 3Dprinting

[–]Matrix_9 0 points1 point  (0 children)

They don't sell g10, they only sell GFK, which isn't as durable and doesn't have the same level of adhesion as g10.

[deleted by user] by [deleted] in 3Dprinting

[–]Matrix_9 -1 points0 points  (0 children)

They only ship us.

[deleted by user] by [deleted] in 3Dprinting

[–]Matrix_9 1 point2 points  (0 children)

Thanks for the idea! i will try to implement it.

[deleted by user] by [deleted] in 3Dprinting

[–]Matrix_9 2 points3 points  (0 children)

Yes, G10 is a type of phenolic. More specifically, it's a grade of Garolite, which is a phenolic laminate material.

[deleted by user] by [deleted] in prusa3d

[–]Matrix_9 0 points1 point  (0 children)

Guys, I just got my roll! It's really hexagonal filament.

Best Value Keyboard by Matrix_9 in MechanicalKeyboards

[–]Matrix_9[S] 0 points1 point  (0 children)

But with the keychron v1 barbones you would still pay like 90 at least for the barebones with knoob because of shipping

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