Linear LED lighting

What is a linear LED strip and why does it matter for interior lighting?

A linear LED strip is a flexible run of light-emitting diodes mounted on a PCB that fits into an aluminium profile and installs in coves, under cabinets, recessed into plasterboard, or along a shelf edge. A driver circuit converts mains power to the correct low voltage (usually 12 V or 24 V DC) that the strip runs on. Linear LEDs are the workhorse of modern indirect and ambient interior lighting plans, replacing older fluorescent tubes and offering precise colour control, dimming, and the ability to hide the light source entirely so only the glow of light appears to come from a surface.

What is LED density and why does it affect how the light looks?

LED density is the number of individual LED chips per metre of strip, commonly ranging from 60 to 240 LEDs/m. At 60 LEDs/m each chip sits roughly 1.67 cm apart; at 120 LEDs/m, about 0.8 cm; at 180 LEDs/m, roughly 0.55 cm. The eye resolves individual point sources at roughly 30 to 50 cm, so wider spacing reads as a dotted line rather than a continuous glow. Low-density strips (60 to 80 LEDs/m) are unsuitable for indirect cove lighting.

For cove lighting, a minimum density of 120 LEDs/m is recommended if the cove is deeper than 20 cm and visible from standing height; at 180 LEDs/m or higher, the light reads as a solid, glowing surface rather than individual points.

What is the difference between constant-voltage and constant-current LED drivers?

An LED strip is powered by a driver that converts mains AC power (230 V, 50 Hz in most of Europe) to a low-voltage DC output, and it comes in two types.

Constant-voltage (CV) drivers maintain a fixed output voltage (typically 12 V or 24 V DC); the strip itself contains resistors that limit current through each LED. CV is the most common residential choice because it is inexpensive and simple, and if part of the strip fails or is removed, the rest keeps working.

Constant-current (CC) drivers maintain a fixed output current (e.g., 350 mA, 500 mA, or 700 mA) and vary voltage to deliver it. The strip must never be opened or shortened without a terminator, since current has to flow in a complete circuit. CC is more expensive and less forgiving, but better for colour-critical or high-brightness applications.

For residential cove and under-cabinet lighting, CV strips with a 24 V supply are the practical standard.

The driver itself is a box (typically 5 cm x 3 cm x 2 cm) that must be accessible for replacement or adjustment. Mount it in a removable access panel, above the ceiling from a loft hatch, or in a kitchen kickspace cabinet or above upper cabinets, with airflow around it and no direct contact with plasterboard. If mounted horizontally, allow at least 5 cm of clearance on all sides.

What is voltage drop and when does it matter in a long LED strip run?

Voltage drop is the loss of electrical potential along the strip's copper traces between the driver and the far end of the run; LEDs there receive less voltage and dim noticeably.

A 12 V system loses about 1 V per 5 to 7 metres, so a 10-metre run can show a visible brightness difference between the near and far ends. A 24 V system is better: the same 10-metre run loses only about 1 V, under 5% and often imperceptible. Some manufacturers offer dual-end wiring for long runs, powering the strip from both ends and eliminating the drop.

A 24 V constant-voltage system is strongly recommended once a run exceeds 5 metres; shorter runs can stay on 12 V. Always verify the maximum recommended run length for the specific strip model, since limits vary by manufacturer.

What role does the aluminium profile play beyond holding the strip in place?

An aluminium profile serves three critical functions: structural support, thermal management (heatsinking), and light distribution (diffusion).

Thermal management. LEDs generate heat. A bare strip with adhesive backing on plasterboard has no heatsink and can reach 70 to 80 degrees Celsius. A continuous aluminium profile in contact with the LED PCB acts as a heatsink, keeping the LED junction temperature 10 to 20 degrees cooler and extending life; without a profile, a strip can dim noticeably after 2 to 5 years of heat-induced degradation.

Diffusion and light distribution. Most profiles include a frosted polycarbonate or acrylic diffuser cover that scatters the light from individual LED points into a smooth, even glow; without it, the naked strip shows visible stripes or bright spots.

Structural rigidity. A bare strip on adhesive backing can sag over time; a rigid aluminium profile screwed to the framing or a mounting ledge keeps it in position, which matters most for runs over 1 metre or oriented horizontally.

Choose the profile type to suit the application: recessed profiles hide the strip flush in a plasterboard recess; surface-mounted profiles are visible but dissipate heat well; corner profiles fit 45-degree mitred corners. Match the profile width to the strip; most strips run 8 to 12 mm wide.

How do dimming methods affect flicker and colour stability in LED strips?

0-10 V analogue dimming. The driver receives a low-voltage signal (0 to 10 volts) that proportionally reduces output, with no flicker and stable colour temperature across the range. It requires a dedicated 4-wire connection (positive, negative, signal, ground) from dimmer to driver, and is the standard for professional installations.

Phase-cut (trailing-edge) dimming. The dimmer cuts off part of the AC mains waveform to reduce the average voltage. It works with some modern LED drivers but not all; incompatible combinations cause flicker or colour shifts, so use it only with a driver explicitly rated for it, never a standard incandescent dimmer.

PWM (pulse-width modulation) dimming. The driver switches output on and off rapidly (typically 1000 to 20000 times per second), and the dimmer controls the on/off ratio to create the impression of reduced brightness. PWM is flicker-free above 1 kHz, simple, cheap, and keeps colour temperature stable.

For residential cove and under-cabinet lighting, specify either 0-10 V dimming or a PWM driver above 3 kHz. Test a sample installation with the intended dimmer before committing to a full retrofit, since flicker or colour shift discovered afterward is expensive to fix.

How is an LED strip recessed into a ceiling or soffit, and what detailing prevents it from being visible?

Recessing an LED strip into a plasterboard soffit or coving gives the effect of seamless, glowing light from a surface, with no visible source.

The typical detail is a continuous rebate cut into the underside of the soffit, roughly 2 to 3 cm tall and as deep as the profile width. The profile sits in this rebate with the diffuser flush with or slightly below the soffit surface; the soffit edge creates a light-shielding lip that hides the source, so the eye sees only the glow, not the strip or profile.

A soffit shallower than 2 cm leaves the profile or diffuser edge protruding, breaking the effect; one too deep wastes space. A depth of 2 to 3 cm is optimal for most residential applications, with LEDs spliced at inside corners using appropriately rated connectors when the rebate runs continuously around a room.

Driver ventilation is also part of this detailing: if it sits in the soffit cavity, ensure airflow around it and no direct contact with plasterboard, mounting it below any insulation line or on a bracket that allows circulation. Trapped heat shortens driver life and can trigger thermal-protect shutdowns.

What are common mistakes in residential LED strip installations?

Undersizing the driver is a frequent error: a driver rated for 100 watts serving a 95-watt strip is thermally stressed with almost no margin. Specify at least 20% spare capacity for a cooler, longer-lasting installation.

Cheap connectors or poor soldering technique are another common mistake: a cold solder joint generates heat, can melt the connector or strip, and causes intermittent failures. Use connectors rated for the voltage and current, and test continuity with a multimeter before powering up.

Failing to plan the driver location before construction is costly: a driver buried in plasterboard or behind drywall needs demolition to reach for maintenance or replacement. Specify its location on the electrical plan and confirm access during coordination.

Installing the strip without a profile and heatsink, relying on adhesive alone, is a false economy: it dims over time from heat degradation, the adhesive eventually fails (especially in kitchens or bathrooms), and there's no diffuser for a smooth glow.

Choosing a dimmer before confirming driver compatibility often results in flicker or colour shift. Test the combination with a sample length before ordering the full installation; if flicker appears, upgrade to a higher PWM frequency driver or specify 0-10 V dimming instead.