RX-LM301-128 Quantum Board Kit: A 355 x 255 mm Substrate, Meanwell OWA-60U, 40-47 V DC at 70 W Max and 2.9 / 3.2 umol/J – and the Figures the Page Leaves Blank

A board-level light engine and a finished grow fixture are different purchases, and the difference is exactly the list of things a buyer has to supply. The RX-LM301-128 is sold as a grow light module kit: an aluminium substrate measuring 14 in by 10 in (355 mm by 255 mm) populated with Samsung LM301 chips plus an added 660 nm deep-red channel, paired with a Meanwell OWA-60U external power supply and rated for a 40-47 V DC input at 0.5-1.5 A with a maximum power of 70 W. The page publishes two efficiency figures, up to 2.9 umol/J for the module and up to 3.2 umol/J for the added deep-red channel, together with a 50,000 hour lifespan and CE, RoHS and FCC listings. It publishes no absolute photon flux, no PPFD, no coverage area, no ingress protection, no beam angle and no warranty. This article explains what each published number commits to, and then shows how to build a defensible plan for a 2 x 2 ft tent from those numbers alone, marking every derived figure as reader arithmetic rather than official data.

Board-level kit: what the term excludes

A board-level kit is a light engine plus a nominated driver, not an appliance. Photosynthetic photon efficacy (PPE) is photosynthetic photon flux divided by wall-plug power, which is why it is expressed in micromoles per joule: it is a ratio, so it is only meaningful next to the power and the drive current it was measured at. A finished fixture adds a housing, an ingress-protection rating, a mounting system, a dimming interface, a thermal design that has been validated as an assembly, and a warranty covering the assembly. A board-level kit deliberately leaves some of that to the integrator, which is why its price per photon can be lower and why the buyer carries more of the design work.

The official page is explicit about the kit’s own content: a Samsung LM301 chip, an added 660 nm deep-red chip, an aluminium substrate of 355 mm by 255 mm, and a Meanwell OWA-60U power supply. Everything an installer needs beyond that, from the mounting frame to the measurement plan, is the installer’s responsibility. This is the single most useful sentence to keep in mind when reading the rest of the specification.

Two efficiency figures on one board, and why they are not interchangeable

The page states “High efficiency grow light module kit, efficiency up to 2.9 µmol/J” and, separately, “Additional 660 nm deep red led chip, efficiency up to 3.2µmol/J”. Two numbers, two scopes. The 2.9 umol/J figure belongs to the module as a whole, meaning the broadband mix produced by the LM301 chips together with the red addition. The 3.2 umol/J figure belongs only to the added deep-red channel. Substituting the higher number for the module as a whole overstates the board, and averaging the two has no physical meaning at all.

The gap between the two figures is also a small lesson in LED physics. Deep-red emitters convert a comparatively large share of electrical energy into photons near 660 nm, where the emission sits inside the photosynthetically active radiation band and close to a chlorophyll absorption region; a broadband white mix spreads its output across the visible band, including wavelengths a plant absorbs less efficiently. That is why a red channel can post a higher photon-per-joule count than the white mix beside it, and why both numbers can be true at the same time. In either case “up to” is an upper bound, not an operating point, and a comparable figure has to come from the same drive current and case temperature as the source. Programmes that qualify horticultural fixtures against defined photon measurements, such as the DesignLights Consortium qualified products list for horticultural lighting at DesignLights Consortium – Horticultural Lighting QPL, exist precisely because these figures are only comparable within a defined measurement protocol.

A 355 x 255 mm substrate is a component size, not a coverage area

The physical board measures 355 mm by 255 mm, about 0.09 square metres of substrate. That number is often misread as a coverage figure. The area that receives light is set by the beam pattern and the mounting distance, not by the board footprint, and the two are only loosely related: a board can illuminate an area several times its own size at a usable density, or a smaller area at a high density, depending on how high it is hung. The official page publishes no beam angle and no coverage figure, so there is no published area to quote. Coverage is something an installer measures or estimates for a chosen height, and the honest way to do it is with a quantum sensor rather than with a division of board size.

Reading the electrical data before choosing a driver

The electrical entry reads “Input voltage: 40~47V, input current 0.5~1.5A, maximum power: 70W”. This is direct-current input, not mains: the board expects a direct-current supply in a 40-47 V band delivering between 0.5 A and 1.5 A, and the assembly is capped at 70 W. The page names the Meanwell OWA-60U as the power supply for the kit, which is the driver the maker matched to this board. The compliance marks, CE, RoHS and FCC, are listed for the product family and cover electrical safety, hazardous-substance limits and electromagnetic emissions.

One disclosure has to travel with this model. The product title on the official site reads “65w QB Led Grow Light RX-LM301-128”, while the body text states “maximum power: 70W”. Both statements sit on the same official page; they are shown here side by side rather than resolved, and neither is presented as a measured value. Anyone sizing a driver, a power budget or a circuit for this board should quote the specific figure the vendor confirms in writing and note which of the two statements it came from.

What the official page does not publish

• Absolute photon flux (umol/s) – not specified in the official datasheet; only a ratio in umol/J is given.
• Absolute PPFD and its measurement height – not specified in the official datasheet; no flux density and no reference plane are stated.
• Coverage area or tent size – not specified in the official datasheet; only the substrate size and the electrical band appear.
• Ingress protection (IP) rating – not specified in the official datasheet; no IP code appears, so humid or wash-down use is not covered by a published rating.
• Beam angle and distribution – not specified in the official datasheet; no photometric data is given.
• Diode count and wavelength ratio – not specified in the official datasheet; the page names chip families, not counts or percentages.
• Warranty, net weight and driver dimensions – not specified in the official datasheet.
• Mounting or hanging guidance – not specified in the official datasheet; no height range is suggested.

Because so much is left open, the useful exercise is not to invent the missing figures but to bound them from the figures that are published, and to label the result as a user-side estimate at every step.

Turning published numbers into a 2 x 2 ft plan (reader arithmetic, not official)

Start with what the page gives: a maximum power of 70 W, and a module efficiency of up to 2.9 umol/J. Multiplying the two gives an upper bound on photon output at the board level of roughly 203 umol/s. This is reader arithmetic, explicitly not an official figure, and it is an over-estimate rather than a rating because maximum power and maximum efficiency are unlikely to occur at the same operating point, and because it ignores driver losses between the wall socket and the board.

Now apply the geometry. A 2 x 2 ft footprint is about 0.61 m by 0.61 m, or roughly 0.37 square metres. Dividing the estimated 203 umol/s by that area gives a zero-loss flux density of about 546 umol/m2/s. Real installations deliver less, because light escapes past the canopy, walls absorb a share of it, and a single board rarely produces a perfectly flat field across a square, so the measured number at the canopy will sit below that ceiling.

Convert to a daily budget. Daily light integral (DLI) is the photon density accumulated over a photoperiod, in moles per square metre per day, and is computed as flux density times 3600 times the photoperiod in hours, divided by one million. At an 18 hour photoperiod, 546 umol/m2/s corresponds to roughly 35 mol/m2/day; at 12 hours, roughly 24 mol/m2/day. Both are reader arithmetic on an over-estimate, and both assume every emitted photon reaches the canopy. The point of writing them down is that the published data is sufficient to place a target range and insufficient to promise a delivered value, which is why the second step has to be measurement. Because the page publishes no PPFD, no height and no coverage, the mounting height for this board cannot be calculated with confidence: set it high, lower the board while reading a quantum sensor at the canopy, and stop when the target density is reached. University extension services document the measurement side of that loop; Michigan State University Extension discusses how light quality and quantity are assessed in controlled environments in MSU Extension – LED lighting for horticulture, and USDA Agricultural Research Service work on plant response to electric lighting at USDA Agricultural Research Service is a reminder that a source rating is not a growth result.

Dimension by dimension: published, derived, and still missing

The table is a division of labour rather than a ranking. Eight rows are anchored by a published value, one row is a disclosed conflict, and four rows are open. Those four open rows are the reason a board-level kit needs a measurement step that a complete fixture does not, and they are also where most of the cost saving sits.

Where a board-level kit such as the RX-LM301-128 fits

A board-level kit fits an integrator who is willing to own the parts a finished fixture would otherwise include. That means a small tent or a rack tier where the board can be mounted on a frame the grower builds, a propagation or mother-plant area where a compact 355 mm by 255 mm light engine is easier to place than a large panel, and any build where the buyer already owns a suitable 40-47 V direct-current supply or the named Meanwell OWA-60U driver. It is also a reasonable choice for experimental benches where several small boards are wanted instead of one large fixture.

It fits less well where the page’s blanks cannot be filled: an environment that needs a published ingress-protection rating, a project that must budget from a certified wattage, or an installation where nobody will be measuring the canopy. In those cases the missing rows matter more than the price difference. The manufacturer is a 17-year LED horticultural lighting manufacturer and lists CE, RoHS and FCC for this kit, which supports export documentation, and the official page positions the kit for grow tents, basement planting, experimental planting and greenhouse planting under a spectrum built for balanced growth with an added deep-red channel for medicinal herb cultivation.

Frequently asked questions

Is the RX-LM301-128 a complete grow light or a kit?

It is a board-level kit. The official page lists a Samsung LM301 light engine with an added 660 nm deep-red channel on a 355 x 255 mm aluminium substrate, plus a Meanwell OWA-60U power supply, a 40-47 V DC input band, an input current of 0.5-1.5 A and a maximum power of 70 W. A finished fixture would also require an enclosure, an ingress-protection rating, mounting hardware, a dimming interface and a warranty; the page publishes none of those, so the buyer supplies or negotiates them.

Why are there two efficiency figures, 2.9 umol/J and 3.2 umol/J?

They have different scopes. The 2.9 umol/J figure describes the module as a whole, meaning the broadband LM301 mix together with the red addition. The 3.2 umol/J figure describes only the added 660 nm deep-red channel. Applying 3.2 umol/J to the whole board would overstate it. Both are “up to” values, so both are upper bounds measured at a drive current and case temperature that the page does not publish.

Does the page give a coverage area or a tent size for this kit?

No. The official page publishes the substrate size, the electrical band and the efficiency, but no coverage area, no PPFD and no recommended hanging height. Dividing the board footprint by a tent footprint does not produce a light-coverage figure, because coverage depends on the beam pattern and the mounting distance. A 2 x 2 ft plan has to be built from a photon-output estimate and then confirmed with a sensor at the canopy.

What power should I plan for, 65 W or 70 W?

Both figures are published on the same official page: the product title says 65 W and the body text says maximum power 70 W. The honest approach is to treat them as a disclosed conflict, size the supply and wiring for the higher figure while leaving a margin, and ask the vendor to confirm in writing which number the delivered unit is specified against. Neither figure should be presented as a measured value.

How should the 50,000 hour lifespan be understood?

The 50,000 hour figure is a lifespan in hours and is a projection from LED and driver reliability data under defined conditions rather than a burn-in test of each kit. Because the board is a component and the driver is a separate item in the same kit, the weaker of the two sets the practical limit, and service life also depends on ambient temperature, drive level and how well the integrator manages heat. The page publishes no warranty term, so the figure is a planning input rather than a commercial commitment.