Friday, December 27, 2013

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LED Phototherapy Unit

is widely thought that light can be therapeutic for the human skin and
soul. Light at the correct wavelength may also be effective against
depression and allergies. There is a wide range of products on the
market, at prices from a few tens of pounds to a hundred pounds or so,
which are presented as universal remedies for dust allergies or hay
fever. If we look at these devices in more detail, we find that their
operation is relatively simple to explain.

Common to all the
devices is that they emit intense red light with a wavelength of 660 nm.
Some biophysicists claim that light of this wavelength can have a
positive effect on the human body and can initiate healing processes.
This so-called ‘phototherapy’ is a treatment which is claimed to have an
effect against allergic reactions in the body, since it acts against
free oxygen radicals and strengthens the immune system, reducing
inflammation of the mucous membrane.

Since this treatment does
not take the form of a medicine, but rather the form of visible light,
there is no risk of side-effects. There has been scientific research
showing that this therapy does not work in every case, but success rates
as high as 72 % have been reported. Since it may not be possible to
obtain these devices under the NHS or under private medical insurance,
our thoughts naturally turn to do-it-yourself. For the enclosure we
decided to use an old nasal hair trimmer.

LED Phototherapy Unit circuit schematic

can be obtained new for a few pounds, or you may have an old one that
can be recycled. The choice of enclosure also dictates the choice of
battery: the unit contains a holder for an AA-size cell. The circuit
must therefore not only be very compact (there is little spare room in
the enclosure), it must also be able to drive a high-brightness red LED
from a voltage between 1 V and around 1.6 V. Here again we can indulge
in a little recycling: we can re-use the circuit from a Mini Project by
Burkhard Kainka for driving a white LED, published in Elektor
Electronics in June 2002.

In this circuit the inductive voltage
pulse is limited by the LED itself, ensuring that the output voltage
will automatically match the forward voltage of the LED. The circuit is
suitable as it stands for driving a high-brightness 660 nm red LED to
make a do-it-yourself phototherapy unit. In view of the small number of
components, the circuit can be assembled by soldering them together
directly or by using a small piece of stripboard.

The circuit can
operate from a wide range of voltages, and so we can use either an
alkaline AA cell or an AA-size NiMH rechargeable cell with a voltage of
1.2 V. The current consumption of the circuit is about 20 mA. Assuming
the circuit has been built correctly, the red LED should light brightly
as soon as power is applied. Five to ten minutes’ use in each nostril
every day should be sufficient to obtain noticeable benefit after two
weeks of treatment.

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