Concept
Since, we had to make a switch that did not require the use of hands, I thought of using wind to switch on the LED lights. The easiest thing to do was to blow onto a metallic strip like aluminium or tin foil, such that the strip would touch another metallic surface to complete the circuit.
This idea of blowing onto something let me develop this project into a device that would act as a spirometer (Fig. below). A spirometer is a device used to test a person’s lung capacity. One would simply blow onto the pipe and try to raise the three balls to the top. The idea of my switch is similar; one would simply blow onto two strips of metallic strip to turn on the two LED lights.
Video
How it Works
I used some copper tapes and joined them together to make two flexible metallic strip. I used a solid metallic sheets such that they stay in place when some wind is applied to it. The idea is to blow onto the copper strip hard enough to light up both the bulbs.
The first metallic strip is thinner and easier to deform, while the second one is relatively thicker and requires more force to make it touch the metallic sheet.
Note: the first circuit lights up the red LED, while the second lights up the yellow.
When a copper strip touches a metallic sheet, they complete the circuit. However, only one copper strip and metallic sheet is associated with one LED light. In other words, the circuit is set up as two parallel circuits as shown in the figure below.
Improvement
The copper strips are set up in such a way that one blocks the wind from the other which only makes it harder to light up the second LED. So, an improvement could be a set-up which does not block wind, but a mechanism which requires more pressured air such that both the lights are lit up.