In my simple and modular cockpit, the controls and switches are not backlit, but I have added a general lighting system that lights-up the controls from a place just below the scenery visual system.
For simple low power lighting with adjustable light intensity, I have used white and yellow (amber) color LED strips, driven by two separate LED drivers, each with dimming capability.
The LED strips are mounted under angles, and some separate units have been
placed at different positions to get relatively equal illumination of the
cockpit panel and some controls. Both left and right side have identical LED
strips, all driven from two LED drivers.
The LED driver schematic is shown below. The Pichler white and yellow LED
strips each consist of 18 sections, where each section has 3 LEDs and a
balancing resistor. All 18 sections are connected in parallel. The LED
driver is build around Richtek RT8470, which is a hysteretic switch mode
step-down converter, capable of delivering max 1A of current. The LED strip
voltage is around 11V, and input voltage needs to be around 15V. Current for
the amber LEDs was set at 300mA total, and for white at 400mA total.
The below circuit also includes several extra components for EMI reduction.
(L1, L4, L5~L8)
The RT8470 ADJ input can be driven with a DC voltage ranging between 0.25V (zero current) and 1.3V (max current). The dimming function It actually chops the LED current at a rate of 300Hz, chopping duty-cycle determined by the ADJ DC voltage.
For this PCB, I have used entirely SMD components, which is a bit different
from normal leaded PCB making. I started out with fully copper covered PCB
and cut the traces (actually copper areas) with Dremel tool. This method
works well for high frequency switch-mode power supplies.
The efficiency of this circuit is high, so there are no hot components to
worry about.
The two potentiometers can be used to separately adjust the white and
amber LEDs. For night flying, I adjust the color to amber.
Below some impressions of the total effect.
Note that the yellow is actually more amber color, but my camera has
difficulties catching the right color.