How it works:
The RLS has three sensors. These sensors are IR (infrared) light proximity sensors. On each sensor there are two parts. The first part
is an IR LED, that is shining a beam of IR light upward. The IR beam is invisible to the naked eye. If you look though your phone's
camera you may be able to see it. The second part is a phototransistor. When the phototransistor is exposed to IR light it allows a
current to pass through..
Since both the IR LED and IR phototransistor are pointed upwards on the RLS, we need something to reflect the IR light back into the
phototransistor. This is where your hand comes in! When you bring a hand closer to the RLS's sensors more IR light is reflected back
into the phototransistor and more current passes through. The microprocessor then reads an analog (read a variable) voltage
produced due to the changing current flowing though the phototransistor. It does this for all three sensors and It uses these varying
voltages to decide how bright to light up the red, green and blue channels of each LED.
Calibration:
Did you know that your TV remote also uses IR light? So that your TV does not change channels by itself, TV manufactures use a
special type of phototransistor that only works when a specific frequency of IR light
is received (typically 38 - 40 khz). The TV
remote is actually flashing an IR signal to the TV!
The type of IR proximity sensors used in the RLS do not have any special filtering. They can pick up stray IR light from other sources.
This will make a series of random colors flow along on your RLS LEDs. We chose not use IR phototransistors with filtering, since all
the models that we tested were either excessively expensive or did not work well to produce a nice smooth analog voltage.
In order to allow the RLS to produce nice smooth color transition and avoid false triggers we added a calibration function. When the
RLS is first powered on (or awoken from sleep mode) the calibration function is run and at any time if you see random LEDs lighting
up, (even when your hands are not near the RLS) simply press the "reset" button and the RLS will re-calibrate.
How to Calibrate your RLS:
As lighting changes or people move around causing both reflections or shadows you may have to recalibrate your RLS.
Remember, IR light is invisible to your eyes so even if you don't see the "light" changing, light on the IR spectrum may have
changed.
When the RLS does a recalibration, it turns off the three IR LEDs on the sensors and then reads the value of IR light coming in. It is
important the RLS be able to see all of the ambient IR light while it is recalibrating. So, it is important that you do not stand too
close to it or put a hand over any sensor while recalibrating. The best way is to place you left index finger to the left of the left
stand and use your right index finger to press the reset button on the lower right hand side of the RLS.
When the RLS does a recalibration it reads the intensity of IR light coming in. It then adds a safety cut-off value to this reading and
will then ignore any IR reading that is below this threshold. What these means for you, is that your RLS will work in many different
lighting conditions. It prefers to be used in areas that are not too bright. Also, when the RLS is calibrated in a bright area, the
threshold is set much higher, so in fact the RLS will be less sensitive to your hand. This means that your hand will have to be closer
to the top of the RLS before it starts to produce colors.