{{ electronic:equipment:gadget:dsc_0034a.jpg?200|Light Mask overview}}
^ 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 If the plug is withdrawn from the socket, the display stays on for about 20 seconds, then fades out.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, counts the number of uses, and directly drives the LCD. 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.
==== Operation ====
As you insert the mask's plug into the "activator" the tip first contacts the B+ pin and connects it to the power regulator, powering up the "activator" - this is all before the plug is fully inserted. The LCD lights up showing "- -" at the top of the digits. The C3 100µF capacitor is also charged at this point. As the plug is inserted further the plug tip reaches the Q1 transistor contact, and the B+ to power regulator connection is connected via the plug's barrel. The C3 capacitor maintains the power during the brief connection interruptions as the plug is being inserted. After a brief delay the LCD display shows the number of sessions left (0 to 30). When the power button is held down for 1 second, if the sessions-left count is greater than 0, the transistor will be switched on, lighting up the mask. At the end of the ten minute timed session, the transistor will be switched off and the session count updated. If the plug is pulled out before the end of the session, the C3 capacitor will continue to power the activator for a few seconds.
==== Components ====
The circuit board contains
* An encapsulated micro-controller chip (COB).
* Quartz crystal (32.768MHz).
* Atmel {{:electronic:datasheet:atmel:at93c46d.pdf|AT93C46D}} serial memory chip: 128 bytes of 8 bits, serial EEPROM.
* {{:electronic:datasheet:fairchild:ss8050.pdf|SS8050}}, NPN, 1.5A power switching transistor.
* HT7533 3.3V low dropout voltage regulator.
==== Modification ====
There are videos ((https://youtu.be/50-48o-jGKM))((https://www.youtube.com/watch?v=LuC4dXrPVZ8)) 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 [[https://deathandthepenguinblog.wordpress.com/2018/01/03/hacking-the-neutrogena-visible-light-therapy-system-to-get-99-lives/|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: [[https://web.archive.org/web/20201207064812/https://github.com/msandres13/neuprog|neuprog]]). And another go at [[https://github.com/brianmgr/NeutrogenaMask|Neutrogena Mask Activator Hack]] using a Raspberry Pi. Not very easy for the average customer though.
Just found this little gem in comments by JJ on [[http://p1repair.com/blog/2017/09/30/neutrogena-light-therapy-mask-eeprom-hack/|Neutrogena Light Therapy Mask EEPROM Hack – 99 uses]]:
^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…^
And it actually works! Well had to do a bit of fiddling about to mount the LCD on the device while open, and that line between R1 and R4 actually connects to the bottom of R3, so you don't even have to scrape the copper trace bare. And I'm not actually totally sure of the sequence needed after connecting R3 to B-. The display shows a "-" over the top of the rightmost digit after touching R3. Trying to short the other two to B- (I think that's what the instruction mean) didn't seem to work easily. But shorting the top of R7 to B- resulted in two "--", one in the centre of each digit, which stayed there for a long time while I poked about, and eventually the display went back to "0" . But try, try, try again, I slipped, and not quite sure which pins got grounded, but it reverted to "30" and now works, and does 10 minute sessions!!
Argghh, the bottom end of J1, C9, and R3 and that wide copper trace between R1 and R4 are all connected to the regulated 3.3V supply. So the above instructions are getting you to short out the 3.3V regulator, and the power dropout simply resets the micro-controller as though it was just powered up. That poor power regulator seems to be able to survive such abuse!
===== Examples =====
{{:electronic:equipment:gadget:dsc_0048a.jpg?800|Light Mask front}}
{{:electronic:equipment:gadget:dsc_0027a.jpg?800|Light Mask back}}
{{:electronic:equipment:gadget:dsc_0028a.jpg?800|Light Mask with activator}}
{{:electronic:equipment:gadget:dsc_0049a.jpg?400|Light Mask activator, top}}
{{:electronic:equipment:gadget:dsc_0050a.jpg?400|Light Mask activator, bottom}}
{{:electronic:equipment:gadget:dsc_0030a.jpg?600|Light Mask switched on, front}}
{{:electronic:equipment:gadget:dsc_0029a.jpg?600|Light Mask switched on, back}}
{{:electronic:equipment:gadget:pc030491.jpg?400|Light Mask red LED}}
{{:electronic:equipment:gadget:pc030493.jpg?400|Light Mask blue LED}}
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===== Tear down =====
{{:electronic:equipment:gadget:dsc_0052a.jpg?800|Light Mask activator opened}}
{{:electronic:equipment:gadget:dsc_0053a.jpg?800|Light Mask activator disassembled}}
{{:electronic:equipment:gadget:pb285602a.jpg?400|Light Mask activator circuit label}}
{{:electronic:equipment:gadget:pb285601a.jpg?800|Light Mask activator circuitboard, top}}
{{:electronic:equipment:gadget:pb285598b.jpg?800|Light Mask activator circuitboard, bottom}}
{{:electronic:equipment:gadget:pb285622a.jpg?400|Light Mask activator LCD, back}}
{{:electronic:equipment:gadget:pb285623a.jpg?400|Light Mask activator LCD connector}}
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===== Modification =====
{{:electronic:equipment:gadget:pb285598a.jpg?800|Light Mask activator hack}}
{{:electronic:equipment:gadget:pb285620a.jpg?400|Light Mask activator hack closeup}}\\
This is the crude modification that hard-wires the battery negative terminal (B-, or Gnd) to the phono socket tip connection, so that the LED mask is powered on immediately when the plug is inserted. There are two disadvantages to this, first there is no longer a timed duration for the exposure, second the LEDs are run at full power which might shorten their life, and give you a stronger exposure than you were expecting.
===== References ======
* [[https://deathandthepenguinblog.wordpress.com/2018/01/03/hacking-the-neutrogena-visible-light-therapy-system-to-get-99-lives|Hacking visible light therapy system to get 99 lives]]
* [[http://p1repair.com/blog/2017/09/30/neutrogena-light-therapy-mask-eeprom-hack/|Light therapy mask EEPROM hack]]
* [[https://www.clien.net/service/board/use/12103135|LED mask activator modifier]]
* [[https://www.reddit.com/r/AskElectronics/comments/5dvu3g/how_to_hack_neutrogena_light_therapy_mask|How to hack light therapy mask]]
If any referenced page no longer exists, try looking for its URL on http://archive.org.
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