Essentia / Devices / Phototherapy Unit

Device Lab 57

Phototherapy Unit

Forty-eight royal-blue emitters on a metal-core board behind a diffuser and a polycarbonate window, in a slim head on an arm over an open cot. Almost everything it radiates falls inside the absorption band, the whole light-facing aspect of the infant is treated at once, and the irradiance at the skin is set by how far above the mattress somebody left the head, which is a number on a scale nobody records and which the geometry of the room keeps changing.

Also called: Bili Light. Arabic: وحدة العلاج الضوئي. Device Lab 57 of 69 in BMEssentia Medical City, 2 configurations.

Overview: the configurations

How it works: the main parts

What each part does, from the Phototherapy Unit lessons in the 3D Device Lab.

Mains inlet, fuse and protective earth

An appliance inlet, a fuse drawer, a rocker switch with a neon leg in it and an earth stud, all on one recessed plate at the back of whichever enclosure the configuration has. The neon is the only thing on either machine that tells you a supply has arrived.

Constant-current driver and output stage

A chassis tray with one populated board in it: reservoir capacitors, a switching transformer, an output stage on a small heatsink, a sense resistor, a connector out to the source, and a screwdriver-slot trimmer that nobody thinks about. That trimmer sets the radiant output of the whole machine.

Heatsink, fan and cooling airway

A finned aluminium block clamped to the source through a thermal pad, a fan in a guarded housing, an intake grille and a set of exhaust louvres somewhere else. On the configuration that hangs over the cot the block is in the head and the fan is not, it is down in the column enclosure, cooling the driver instead.

Control fascia and irradiance selector

A raked panel with a small display window, five membrane keys, a rotary drive selector and printed legends beside all of them. Read it from end to end and the significant thing is what is not on it: there is no irradiance anywhere, and there is a greyed line of text saying so.

Treatment timer and source-hours counter

Two counters behind the same fascia, and the difference between them is the point. One is a digital window that counts this treatment and is reset by a key.

Thermal cut-out and source-fail detection

Two small, unglamorous circuits that between them are the only automatic protections on the machine. A bimetal disc clamped to the source’s thermal path with a relay in series with the source, and a comparator watching the driver’s sense shunt for a source that has gone open circuit.

Hand-held spectral irradiance meter

A moulded hand-held box with a small display, two keys, a band-select switch, and a sensor head on a lead. It is not part of either machine, it is the only thing in the system that knows the dose, and on most units it lives in a drawer.

Distance-irradiance chart and rating plate

A printed label on the back of the enclosure with a short table on it: a distance in one column and an irradiance in the other, a waveband, and the words "new source". Beside it a rating plate giving the source type and the electrical classification.

Explore it in the Device Lab

• Two lamps that look the same and differ sixfold: Fit four different sources in turn at the same drive and the same distance, and watch two numbers move in opposite directions: the irradiance inside the absorption band, and how bright the thing looks.
• The falloff, and why it is not inverse square: Sweep the head from a hundred and fifty millimetres to seven hundred and watch the irradiance. Then plot what an inverse-square law would have predicted from one of those readings, and look at the gap.
• The third factor, and it is a nappy: Hold the irradiance fixed and change nothing but what the infant is wearing and how it is lying, and watch the dose rate move by a fifth.
• What ninety per cent of a lamp is thrown away for: On the contact configuration, take the band-pass out of its holder and watch two numbers rise. One of them is the blue irradiance, which looks like an improvement. The other is the total irradiance at a pad that is against skin.
• The only feedback path, and nobody checks it: There is exactly one instrument in this system that measures the quantity the treatment depends on, and it belongs to neither machine. Put the fault in it and watch what happens: nothing. There is nothing in the device that can disagree with it.

Common faults and what to check

Most reported device problems (FDA MAUDE)

Raw counts of adverse event reports for this device type (FDA product code LBI), all years. Not adjusted for the number of units in use, so they show what gets reported, not failure rates. Report text is never copied.

Standards engineers test against

Recent FDA recalls

From the FDA recall database (openFDA), newest first, imported 2026-10-22. 14 recalls on record for this device type. Recall text is the FDA's public text; each recall links to the official record.

Learn it, see it in 3D, ask about it

• Ask Essentia about the Phototherapy Unit: answers from named sources, with the device open in its 3D Device Lab beside the answer.
• The Phototherapy Unit on the BMEssentia Platform: the Device Library course, 13 sections from physics to maintenance.
• BMEssentia Medical City: Device Lab 57, the Phototherapy Unit fully assembled in 3D, with lab tasks and the simulations.

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