Dave_H
Flashlight Enthusiast
VLC stands for Very Low Cost 
I have been using small cheap touch LED table lamps for a few years. They are convenient
and work remarkably well for the price ($4 typically) as sources of low-level light
for short intervals. These run from 3xAA, some also from 5v through USB jack. Some versions
have rechargeable battery, at higher cost.
There are different styles including a bendable "gooseneck" or with head which folds
up or down. One brand name is Voltax (for reference, not an endorsement).
One lamp initially did not work, and its low cost and return inconvenience made me want
to fix it myself if possible.
Removing four screws from the bottom revealed a small PCB, having control IC SGL8022W.
A small copper touch pad connected to this chip by a wire had detached from top of plastic
case. By sticking it back on, normal operation was restored.
(besides, for cheap returned device hardly worth cost of repair, it would likely be junked;
so it was saved from landfill).
The lamp has low-medium-high settings with each touch, but no memory of desired setting
so you have to cycle through to the level you want, and to turn it off, which is mildly
annoying (though you get used to it).
From what I can tell, circuit uses linear (not switching) current regulation with PWM dimming.
Datasheet for the SGL8022W is available and although language is a bit difficult to follow,
chip has different control modes, including on/off and continuous (versus 3-step) dimming.
This is set by two IC pins connected either to positive supply or ground.
http://www.mikrocontroller.net/attachment/214214/20130601111832.pdf
On PCB was found two IC mode pins OPT1 (pin 6) and OPT2 (pin 8) connected to ground
which gives 3-stage control as detailed in datasheet. By carefully desoldering pin 6 and bending
it up from its PCB pad, then connecting to a short wire to V+ (battery + wire), I was able to
change mode to on/off (short touch) with continuous up/down dimming (long touch). Brightness
level is maintained over off/on cycles.
I also have a small LED under-counter strip light about a foot long, 24 SMT LEDs, 3W,
3-stage touch brightness, runs from 12vdc, looks and works great. It uses QT168X control
chip which is visible through the clear top. It operates in similar fashion: low-medium-
high-off. Have not found datasheet for it yet, considering a similar mod.
Dave
I have been using small cheap touch LED table lamps for a few years. They are convenient
and work remarkably well for the price ($4 typically) as sources of low-level light
for short intervals. These run from 3xAA, some also from 5v through USB jack. Some versions
have rechargeable battery, at higher cost.
There are different styles including a bendable "gooseneck" or with head which folds
up or down. One brand name is Voltax (for reference, not an endorsement).
One lamp initially did not work, and its low cost and return inconvenience made me want
to fix it myself if possible.
Removing four screws from the bottom revealed a small PCB, having control IC SGL8022W.
A small copper touch pad connected to this chip by a wire had detached from top of plastic
case. By sticking it back on, normal operation was restored.
(besides, for cheap returned device hardly worth cost of repair, it would likely be junked;
so it was saved from landfill).
The lamp has low-medium-high settings with each touch, but no memory of desired setting
so you have to cycle through to the level you want, and to turn it off, which is mildly
annoying (though you get used to it).
From what I can tell, circuit uses linear (not switching) current regulation with PWM dimming.
Datasheet for the SGL8022W is available and although language is a bit difficult to follow,
chip has different control modes, including on/off and continuous (versus 3-step) dimming.
This is set by two IC pins connected either to positive supply or ground.
http://www.mikrocontroller.net/attachment/214214/20130601111832.pdf
On PCB was found two IC mode pins OPT1 (pin 6) and OPT2 (pin 8) connected to ground
which gives 3-stage control as detailed in datasheet. By carefully desoldering pin 6 and bending
it up from its PCB pad, then connecting to a short wire to V+ (battery + wire), I was able to
change mode to on/off (short touch) with continuous up/down dimming (long touch). Brightness
level is maintained over off/on cycles.
I also have a small LED under-counter strip light about a foot long, 24 SMT LEDs, 3W,
3-stage touch brightness, runs from 12vdc, looks and works great. It uses QT168X control
chip which is visible through the clear top. It operates in similar fashion: low-medium-
high-off. Have not found datasheet for it yet, considering a similar mod.
Dave
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