■ The top of the lamp driver printed circuit board.
The eight-pin IC produces a sine wave at 44. 4 kHz to
drive a small transformer that produces the 470 Vpp
needed to power the tiny mercury lamp.
case by removing three screws from the back and
pop the case open. Once opened, take out the
three screws holding the PCB to the case. Once
free, the printed circuit board looks like what you
see in the photos.
There’s no ON-OFF switch on the Den Tek
toothbrush sanitizer. Instead, there’s a
momentary pushbutton switch that’s activated by
a small tooth in the lid of the case. There are six
contacts on the switch with three on each side
of it. The switch leads are soldered to two PCB
copper pads (two leads on the first pad and the
other four on the second pad). The red wire (+3V)
must be moved to the other pad to electrically
bypass the switch. The photo shows the PCB pads
I’m talking about.
I spliced a two-cell AAA battery pack to the PCB’s red
and black wires. I chose not to incorporate a switch since
I’ll be the only person turning the UV lamp on and off.
This means to power the UV lamp on and off, I either put
the batteries into their holder or remove them. You may
opt to add a switch. In that case, you can either solder a
toggle switch between the battery holder and the PCB or
use a AAA cell holder with built-in switch.
Avoid exposure to the UV lamp. When energized, the
lamp produces UV-C at a wavelength of 254 nm, which is
harmful to DNA in cells (this includes bacteria, fungi, and
viruses). The direct damage from UV-C occurs when UV
photons convert the hydrogen bonds (weak bonds formed
by electrostatic attraction) between some nucleotides in a
DNA strand into covalent bonds (stronger bonds where
electrons are shared between atoms). Since the covalent
bond is stronger, the DNA is unable to unzip itself for
gene expression and DNA replication. Basically, covalent
bonds foul the operation of the DNA machine and so the
I mounted two UV-C lamp circuits alongside the LED
UV-A bank inside my near space environmental chamber.
The new and improved UV bank sits at the top of the
■ On the bottom of the printed circuit board, you’ll find
the power wires. You can’t miss which wire is positive
and which is ground since they’re properly colored coded
and the PCB is labeled.
chamber where it shines light on the victim below.
Experiments inside the chamber get exposed to intense
cold, bright UV, increased ionizing radiation, and a
vacuum (which feels like home in near space). In future
experiments, I’ll expose cell cultures to these conditions to
see which can still multiply afterwards. Experiments like
this can identify microorganisms that could potentially
survive a trip from Earth to Mars after being blasted off
the Earth by a meteorite impact.
The next stage for the near space environmental
chamber is to find a better radiation source (that includes
adding betas and gammas) and an affordable UV-B
source. Once I locate these, you can count on me to write
about it in N&V.
Onwards and Upwards,
Your near space guide NV
■ With the lamps
off, this UV bank
■ But apply power and it’s a DNA
nightmare. Apparently, my digital
camera has a problem adjusting
exposure time and focus in UV light.
■ Melt the solder holding the red wire to its current pad
and pull it free. Then, place the wire in contact with one of
the two solder pads on the other side of the switch and
solder it back down.
May 2010 69