Technical Articles & Guides

XineLam · Zhongshan City Ruixian Electronics Factory

Long-form, source-referenced guides on LED lighting for plants. Every article states its figures with the conditions they were measured under, links to the primary literature or industry standards behind each claim, and keeps product references to the short sections where they are genuinely relevant. New guides are added regularly.

Grow light technology

• How Much Electricity Does a Grow Light Use? A Practical kWh and Cost Guide

  Input watts, photoperiod and tariff turned into a monthly kWh table for four fixture classes, plus the cost per mole of delivered light and the loads a lighting estimate usually misses.

  Published 20 October 2026

• Do Plants Need UV and Far-Red Light? What the Evidence Shows

  What far-red does inside photosystem cooperation, why UV behaves as a dose-dependent stressor rather than a nutrient, and how each waveband should be specified and measured.

  Published 20 October 2026

• How Many LED Grow Lights Can Run on One Circuit?

  How to read a fixture's rated input current, apply the 80% continuous-load allowance, and work out how many lights one branch circuit will carry at 120 V and 240 V.

  Published 14 October 2026

• Do LED Grow Lights Flicker? Driver Ripple, PWM Dimming and the Metrics

  Why an LED follows its driver current almost instantly, what percent flicker and the stroboscopic visibility measure describe, and which waveform data to request from a supplier.

  Published 14 October 2026

• How to Design a Vertical Farm Lighting Layout for Microgreens

  How to set a DLI target, a photoperiod and a tier height for a microgreen rack, with a PPFD-to-DLI conversion table and a worked example for a four-tier rack.

  Published 13 October 2026

• How Does Blue Light Affect Leafy Green Growth and Plant Shape?

  What controlled trials measured when the blue fraction of total photon flux was varied: leaf expansion, elongation, fresh weight and anthocyanin, plus a goal-by-goal selection table.

  Published 13 October 2026

• Do Seeds Need Light to Germinate? Light, Darkness and Phytochrome Explained

  Most crop seeds germinate in the dark, while lettuce and a few weeds respond to light through phytochrome. Sowing depth, and the point at which to switch the grow light on.

  Published 7 October 2026

• Can Light Reduce Powdery Mildew? UV and LED Treatments in Greenhouses

  How UV-C, UV-B and visible light suppress powdery mildew, why treatments are run at night, and where the dose and safety limits lie.

  Published 7 October 2026

• Are LED Grow Lights Waterproof? IP Ratings Explained

  What IP65, IP66, IP67 and IP68 mean under IEC 60529, the water tests behind each level, and which rating a greenhouse, propagation room or grow tent actually needs.

  Published 21 September 2026

• Signs of Too Much Light on Plants: Bleaching and Light Burn

  How to recognise light burn, bleaching and photoinhibition under LED grow lights, separate them from nutrient problems, and correct the cause with measured PPFD and DLI.

  Published 21 September 2026

• How Much Does It Cost to Run an LED Grow Light?

  Convert watts and hours into kilowatt-hours, apply your own electricity rate, and see what 60-600 W fixtures cost to run, with tariff and photoperiod comparison tables.

  Published 15 September 2026

• Can I Use a Regular LED Bulb as a Grow Light?

  What an ordinary household LED bulb can and cannot do for plants, how PAR, PPF and PPFD differ from lumens, and when a dedicated fixture pays off.

  Published 15 September 2026

• How Far Should LED Grow Lights Be From Plants?

  Recommended hanging distances by growth stage, why PPFD falls faster than most distance charts assume, and how to set fixture height from a PAR meter reading.

  Published 14 September 2026

• Are LED Grow Lights Safe for Your Eyes?

  What the blue light hazard actually measures, how IEC 62471 risk groups classify lamps, and what European health reviews conclude about grow-light eye exposure.

  Published 14 September 2026

• Do LED Grow Lights Produce Heat? Radiant and Convective Heat Explained

  Every watt of fixture input leaves as photons or as heat. Sets out where the energy goes, why the radiant-to-convective split changes canopy temperature, why a lighting upgrade shifts the heating and cooling balance, and how to convert fixture wattage into a cooling load.

  Published 12 September 2026

• Do Plants Need UV Light? UV-A, UV-B and the UVR8 Response Explained

  Ultraviolet sits outside the photosynthetic waveband and supplies no energy, yet plants read it as a signal through the UVR8 receptor. Separates the UV-A, UV-B and UV-C bands, walks through the signalling cascade, and reports measured dose-response results from controlled lettuce trials.

  Published 12 September 2026

• How to Size an LED Grow Light: PPFD, DLI and Efficacy Explained

  A four-step sizing method that uses only plant-relevant units — PPF, PPFD, DLI and photosynthetic photon efficacy. Includes crop DLI reference values, a PPFD-to-DLI conversion table, and a running-cost comparison across fixture efficacies.

  Published 11 September 2026

• Does Far-Red Light Increase Plant Growth? R:FR Ratio and the Emerson Effect

  Far-red sits outside the PAR waveband, so it is missing from most fixtures' headline output figure, yet plants read it. This guide separates the phytochrome signalling effect from the photochemical Emerson enhancement effect, and sets out the measured dose ranges and trade-offs.

  Published 11 September 2026

• How Long Do LED Grow Lights Last? L70, LM-80 and TM-21 Explained

  LED luminaires fade rather than fail. How L70, LM-80 and TM-21 define rated life, why the standards' 6X rule caps long projections, what the horticultural industry actually reports, and how to plan replacement around PPFD depreciation rather than a marketing number.

  Published 11 September 2026

• How Many Hours Should LED Grow Lights Be On? A Photoperiod Guide

  How day length differs from daily light integral, the hours per day advised for indoor growing, and how schedules change by growth stage.

  Published 16 September 2026

• LED Grow Light Wattage: Actual Power Draw vs Equivalent Rating

  What an equivalent wattage rating really means, how to find a fixture's rated input power, and which metrics actually predict plant light.

  Published 16 September 2026

• How to Measure PPFD Without a Quantum Sensor: Six Practical Options

  Six ways to obtain a PPFD figure without owning a quantum sensor — lux conversion factors, phone apps and fixture maps — with the error each one carries and a PPFD-to-DLI conversion table.

  Published 17 September 2026

• Constant Current vs Constant Voltage LED Drivers: How to Choose

  What each driver type regulates, how to check an output window against an LED string, which dimming interfaces apply, and the standards behind the label.

  Published 17 September 2026

• What Color Light Do Plants Need? Red, Blue and White LED Spectra Compared

  How blue, red and far-red wavelengths act on plants, what controlled studies measured at each wavelength, and how to read the spectrum figure on a fixture.

  Published 18 September 2026

• Greenhouse Supplemental Lighting with LEDs: When It Pays Off

  The daily light integral thresholds below which greenhouse supplemental lighting clearly pays, the seasonal window, and a dimension comparison of LEDs against discharge lamps.

  Published 18 September 2026

• Why Do LED Grow Lights Have Fans? Active vs Passive Cooling Explained

  Where the heat inside an LED grow light comes from, how active and passive cooling differ, and how to tell when a fixture is running too hot.

  Published 19 September 2026

• Do LED Grow Lights Work With Smart Plugs and Timers?

  What happens when an LED driver is switched by a timer or smart plug, why inrush current matters, and how to compare the control methods.

  Published 19 September 2026

• How Much Light Do Microgreens Need? PPFD, DLI and Photoperiod

  Microgreens light requirements by stage: published PPFD and DLI ranges, a PPFD-to-DLI conversion table, the dark period after sowing, and where trays are most often under-lit.

  Published 22 September 2026

• How Even Is Your Grow Light? Measuring PPFD Uniformity and Fixing Hot Spots

  Why an average PPFD figure hides hot spots and dim edges: how CV and min/max ratios describe spread, how many points to measure, and which fixture changes actually flatten a canopy.

  Published 22 September 2026

• How to Compare LED Grow Light Efficacy: µmol/J Explained

  What photosynthetic photon efficacy measures, why the fixture figure is lower than the LED datasheet, and the published reference values worth checking.

  Published 23 September 2026

• Grow Light Uniformity: How to Read PPFD Distribution and Edge Drop

  How to measure PPFD across a canopy with a grid, why the minimum-to-average ratio misleads, and how mounting height drives edge drop.

  Published 23 September 2026

• Does Adding CO2 Let Plants Use More Light? The Light Saturation Point Explained

  How the light saturation point works, why sealed rooms drift below ambient CO2, and the enrichment levels and timing that are actually reported.

  Published 27 September 2026

• Which Light Is Best for Seedlings and Cuttings? A Propagation Lighting Guide

  The five criteria that matter when lighting a propagation bench, how fluorescent, MH, HPS and LED options compare, and how to set photoperiod and height.

  Published 27 September 2026

• Why Are My Seedlings Leggy? LED Grow Light Distance and Intensity Fixes

  How to diagnose seedling stretch with a daily light integral target, the PPFD-and-hours arithmetic behind it, and the day-night temperature gap that also stretches plants.

  Published 28 September 2026

• PPFD vs Lux: Which Should You Measure for Grow Lights?

  Why lux is weighted to human vision and PPFD counts photons, the published conversion factors that differ by lamp type, and what to measure instead.

  Published 28 September 2026

• LED Grow Light Dimming: How to Use a Dimmer at Each Growth Stage

  The four dimming interfaces found on horticultural LED drivers, why intensity should follow the growth stage, and how to convert a target DLI into a dim setting.

  Published 29 September 2026

• Reflective Walls in a Grow Room: How Much Extra PPFD Do They Add?

  Specular versus diffuse reflection, a practical material comparison, and measured greenhouse results showing how much the surface choice matters.

  Published 29 September 2026

• How to Light a Vertical Farm: Multilayer Rack Lighting Design

  The design order for rack lighting: set a DLI target, convert it to PPFD and photoperiod, fix layer height, then check uniformity and heat load.

  Published 30 September 2026

• What Light Do Tissue Culture Plants Need? PPFD, Spectrum and Photoperiod

  What in vitro cultures actually receive: the working PPFD range, how blue and red ratios affect proliferation, and why 16 hours is the default photoperiod.

  Published 30 September 2026

• Do Plants Use Green Light? How Green Wavelengths Work in a Canopy

  Leaves absorb about 80% of green light and transmit roughly 10%. How green wavelengths drive photosynthesis and why they reach deeper into a canopy.

  Published 5 October 2026

• Can Light Quality Change Crop Nutrition? How LED Spectra Affect Phytochemicals

  Light quality steers secondary metabolism: in controlled studies blue LED raised total phenols 55% and flavonoids 66% over fluorescent light.

  Published 5 October 2026

• LED vs HPS Grow Lights: Efficacy, Spectrum and Heat Compared

  Photon efficacy, spectrum, heat path and control compared, plus the measurements to run before you specify a fixture.

  Published 6 October 2026

• How Long Should Grow Lights Stay On? Photoperiod and Dark Periods Explained

  Turning a daily light integral target into light hours, why the dark period is a reserved block, and example schedules by crop stage.

  Published 6 October 2026

• What Red-to-Blue Ratio Should an LED Grow Light Use?

  What red and blue photons each do, what the lettuce research actually supports, and how to pick a red:blue ratio for your crop.

  Published 8 October 2026

• Do LED Grow Lights Need a Ballast?

  Why an LED needs a driver rather than a ballast, how the two differ in wiring and dimming, and what to check before retrofitting an HID fixture.

  Published 8 October 2026

• PPF vs PPFD: What Is the Difference in Grow Light Metrics?

  PPF describes what a luminaire emits, PPFD describes what the canopy receives: where the two units differ, how they convert, and how to read both on a datasheet.

  Published 9 October 2026

• How to Read a Grow Light Spectrum Chart: Peaks, Ratios and Claims

  A spectrum chart shows the shape of a fixture's output, not how much light there is. What the axes mean, what the curve hides, and what to ask for instead.

  Published 9 October 2026

• What Is Light Burn on Plants and How to Prevent It

  Light burn is the damage a plant shows when it absorbs more light than it can use. The mechanism, how to tell it from nutrient burn and heat stress, and how to correct it.

  Published 10 October 2026

• What Is PAR and How Does It Differ From Lux?

  PAR is the 400-700 nm waveband plants use for photosynthesis; lux is weighted to human vision. What each unit measures, and why no fixed conversion exists.

  Published 10 October 2026

• LED Grow Light Lifespan: What L70, L90 and TM-21 Really Mean

  How the L70, L80 and L90 lumen maintenance points are defined, how IES LM-80 test data feeds an IES TM-21 projection, and why a rated life is not a warranty.

  Published 12 October 2026

• LED Binning Explained: Why Bin Codes Matter for Grow Light Performance

  What LED binning actually sorts, how chromaticity, flux and forward voltage bins are defined, and why two grow lights with the same CCT can still differ.

  Published 12 October 2026

• How Do Grow Lights Control Flowering? Photoperiodism Explained

  Flowering in most plants is triggered by the length of uninterrupted darkness, not the number of daylight hours. Sets out the photoperiod classes, how phytochrome reads night length, and how to set a light schedule without breaking the dark period.

  Published 15 October 2026

• LED Grow Light Bars vs Panels: Which Form Factor Fits Your Grow Space?

  Bar and panel fixtures differ mainly in emitting area, which fixes their distribution, edge drop and how readily neighbours overlap. A dimension-by-dimension comparison and a geometry-first selection procedure.

  Published 15 October 2026

• Does Interlighting Pay Off in Tall Crops? Under-Canopy LED Lighting for Tomatoes and Cucumbers

  Interlighting moves part of the LED light inside the canopy instead of leaving it all above the crop. What the research measures, and how to set a light ratio.

  Published 16 October 2026

• How Much Light Does Your Greenhouse Glazing Really Transmit?

  Transmittance figures by glazing material, what removes those numbers in service, and how to turn the gap into a supplemental lighting decision.

  Published 16 October 2026

• Do Grow Lights Need Lenses or Reflectors? Beam Angle, Coverage and Distribution

  Beam angle, lenses and reflectors decide where photons land rather than how many are emitted. Published distribution figures, an optic comparison table and a measurement routine.

  Published 17 October 2026

• Why Do Transplants Burn Under Grow Lights? Photoinhibition and Light Acclimation

  Bleached leaves are usually an acclimation problem rather than simply too much light. What photoinhibition is, how plants defend themselves, and a ten-day ramp.

  Published 17 October 2026

• How to Calculate Cooling Load for an LED-Lit Grow Room

  A step-by-step method from fixture watts to BTU/h, latent load and equipment capacity, with a worked example and a load table.

  Published 19 October 2026

• LED Grow Light Inrush Current: Why Breakers Trip and How to Size Circuits

  Why a correctly sized breaker still trips at start-up, how trip curves behave, and six ways to design the circuit around inrush current.

  Published 19 October 2026

• Why Do Two PAR Meters Disagree Under the Same LED Grow Light?

  Spectral response and calibration source explain why two sensors read the same bench differently, plus how to compare them fairly.

  Published 21 October 2026

• Why Do LED Grow Light Drivers Fail in Hot Grow Rooms? Derating Explained

  Case temperature, capacitor life and derating curves decide how long a grow light really lasts at 40 degrees.

  Published 21 October 2026

About the publisher

Zhongshan City Ruixian Electronics Factory (XineLam) has 17 years of experience designing and manufacturing LED lighting, and holds 300+ patents in China and internationally. The articles on this page are written as technical reference material for growers, specifiers and researchers; they are not product brochures.