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Gadget data
Model	Light Therapy Acne Mask
Manufacturer	Neutrogena

This mask shines red and blue visible light onto the face, the red to reduced inflammation and the blue to kill acne bacteria. It is powered by four AA cells in an “activator” which provides thirty, ten minute, sessions. Despite promotional advertising which would suggest otherwise, the limit of thirty sessions is simply a ploy to require you to make ongoing purchases to continue to use the device. The batteries are replaceable, there is no evident reason for the “activator” to wear out, or degrade in performance after any number of uses, let alone thirty.

When the mask is plugged into the “activator” its LCD displays the number of sessions left. In fact the LCD turns on when the tip of the power plug lifts the first contact of the socket, before the plug is fully inserted. When the power button is held down for one second, power is applied to the LEDs and a new session starts. If the plug is withdrawn from the socket, the display stays on for about 20 seconds, then fades out.

Hardware description

The mask contains twelve blue LEDs, and nine red LEDs. They have a faded power on and off sequence, and run at a constant current for the duration of the ten minute session.

The “activator” contains four AA cells, a two digit LCD and a double sided circuit board (L-D E327501 “Universal Controller Gen-2.7” Rev A3).

A micro controller controls the power on/off, times the sessions, and counts the number of uses. The sessions are recorded in the 16bit serial eprom.

The power to the microcontroller is regulated by a 3.3V LDO linear regulator. The regulator and an NPN transistor are used to supply a constant current to the LEDs.

Components

The circuit board contains is one encapsulated controller chip, a serial memory chip (Atmel AT93C46D, 64 words by 16 bits, serial EEPROM), a quartz crystal (32.768MHz), a power switching transistor (SS8050, NPN, 1.5A), and a voltage regulator.

Modification

There are videos ¹⁾²⁾ showing an extremely crude hack to the activator, which wires the device “on” continually while plugged in (basically shorting out all the control circuitry). No power control, no timer (ie no safe-guards). The product has been withdrawn due to possible eye hazards to some people (it has a built in amber filter in front of the eyes, that provides little protection as the light can reach the eyes passing directly underneath it), obviously using the device for an unlimited time (rather than 10 minutes), would greatly increase any hazard.

There is also a great series of articles about reprogramming it Hacking the Neutrogena visible light therapy system to get 99 lives using an Arduino, which retains the timer function and power regulation (This hack modified for Raspberry Pi here: neuprog). And another go at Neutrogena Mask Activator Hack using a Raspberry Pi. Not very easy for the average customer though.

Just found this little gem: “It’s easy to reset this version of the board back to 30. Find the terminated line in the space between R1 and R4. Using a sharp knife, scrape the surface of the line to expose the conductive material. Next take a long wire and connect it to B-. Now take the other end of the wire and touch it to the exposed line for a second, you should see the lcd flash – – . You now have about 2 seconds to take the same wire and bridge the tops of R7 and J1. The lcd should now show 30. Make sure you change out the batteries too, they drop in voltage right around the 30 use mark. Much easier than reflashing…” in comments by JJ on Neutrogena Light Therapy Mask EEPROM Hack – 99 uses!