Build Journal

Before we commit to 320 medical-grade laser diodes and the thick end of £800, we are building a four-diode bench rig. The logic is embarrassingly simple: if the firmware, the MOSFET choice, or the current-set resistor is wrong, a full batch is a full batch wasted. A four-diode string tests 100% of the electrical design at roughly 1% of the cost. The small experiment proves the big design, one scaled copy at a time, and we would rather discover an awkward truth for £15 than for £800.

The other reason to build something physical now is that the software cannot be validated against an idea. The iOS app, the BLE pulse protocol, and the three PWM modes — Continuous, Super-pulse 10 Hz, and Super-pulse 1 kHz — all need a real diode, really switched, really driven, before we can trust any of them. Four diodes is enough to exercise every code path end-to-end: session start, mode switch, current regulation, thermal cut-out, OTA recovery. If the firmware behaves on four, the same firmware on 320 is a scaling problem, not a correctness problem.

There is also the unglamorous matter of wiring. Hand-soldering four diodes in series with a ballast resistor and a FET is the same task we will repeat roughly 80 times inside the actual helmet shell. If that joint is fiddly at scale one, it is punishing at scale 80, and every small indignity compounds. Better to find out now which lead length is awkward, which jig we actually need, and which step we keep getting wrong, while the cost of redoing it is a fresh bit of solder rather than a scrapped sub-assembly.

What the bench rig really is, then, is the whole product compressed into one solderable unit: four diodes, a resistor, a FET, and an ESP32 running the real firmware against the real app. If that survives a 20-minute session at the target irradiance without drifting, overheating, or dropping BLE, the 320-diode build is the same circuit replicated — not a new problem to solve. We have not assembled it yet. This is us writing down the reasoning before we switch on the iron, so that if it does not work, we at least know what we thought we were testing.

Today we pushed helioscap.co.uk live and opened the waitlist. It is a small moment on paper but it is the first time the product has a public face: a home page, a clear price, and an explanation of what the Helios 320 Laser Helmet actually is. Getting here took far longer than the code itself suggests, because every sentence on the page is an argument we had to settle internally first.

Our positioning is deliberate. We are not a subscription, we are not a clinic, and we are not a miracle. We are a one-off purchase of a well-engineered device, backed by the physics of low-level laser therapy and priced at a level where a motivated person can commit without a finance agreement. £999, ships from the UK, no tricks.

The waitlist exists so we can size the first production run honestly. We would rather under-promise on timing and over-deliver on the device than chase every pre-order dollar. If you are on the list, you will hear from us before anyone else when the first batch is ready.

The number in the product name is not marketing. 320 is the count of medical-grade 650nm laser diodes we are fitting into the Helios shell, and we arrived at it by working backwards from coverage density rather than forwards from a spec sheet. Most competing devices in the consumer bracket sit between 80 and 272 diodes, with the higher end reserved for clinic-tier pricing.

The argument for more diodes is not that more light is always better. It is that above a certain density, every follicle across the treatment area sees meaningful irradiance simultaneously, so you can hit the evidence-backed dose in a single session people will actually sit through. We modelled scalp coverage against an adult head and landed on 320 as the density that delivers the 3–6 J/cm² target across the full scalp — temples, sides and back included — in a 20-minute session, three times a week. That is the protocol the peer-reviewed LLLT trials consistently use.

There was a real cost to this choice. Driver electronics, thermal management, and shell geometry all had to be redesigned to handle the additional current and heat. We decided that was the right tradeoff, because compliance is the real bottleneck in at-home light therapy, and a device you use is worth more than a device that spec-sheets well.

We started this project calling it Helios Cap and we are not going to rename the company, but internally the form factor debate was the single most consequential call of the quarter. A cap is friendlier, lighter, and cheaper to tool. A helmet is rigid, covers the full treatment area consistently, and does not rely on fabric tension to keep diodes at the correct distance from the scalp.

The moment we mocked up both, the helmet won on the only metric that mattered: repeatability. With a cap, the gap between the diodes and the scalp varies with fit, posture, and how recently you washed your hair. With a rigid shell sized to the 50th-to-95th percentile adult head, the geometry is fixed. Fixed geometry means the dose you get today is the dose you get in six months.

We will keep the brand name Helios Cap because it is what people search for and it is how we introduced ourselves. But the product on the box and in your hands is a helmet, and every piece of our copy now says so.

The origin story is almost embarrassingly simple. One of us started thinning in his mid thirties, tried the usual pharmaceutical routes, did not love the side effect profile, and went looking for a device-based alternative. What he found was a market split between £3,000 clinic caps and £200 Amazon novelties, with very little in the middle that an engineer could look at and take seriously.

So we did what engineers do when they cannot buy the thing they want: we started specifying it. Helios is named for the Greek sun god because the underlying mechanism is photobiomodulation, because Hephaestus Ventures already leans into the Greek pantheon, and because we wanted a name that sounded confident without sounding clinical.

The goal from day one has been a device you would be comfortable recommending to a friend. Honest claims, honest price, honest country of manufacture. That is the whole pitch, and the rest of this journal is us working out how to honour it.