LED Phototherapy Unit


It 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

LED Phototherapy Unit Circuit Diagram

These 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.

Author: Jörg Trautmann – Copyright: Elektor Electronics Magazine


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