Blink Sensor With Sigmoid Function

A simple Arduino project made more complicated! Has the rate which two LEDs flash depending on the environment, uses the Sigmoid function.

Sigmoid Function

The sigmoid function is a bounded, real function. Its bounded by two horizontal asymptotes as x approaches positive and negative infinity. Graphically, the function produces an "S"-shaped curve.

The function is represented by the formula:

Why the Sigmoid Function?

In simple terms, since the function both has an upperbound and a lowerbound asymptote, we can have the speed at which the LEDs blink never go too fast or too slow. (Basically, I know that flashing lights are bad for the eye and I am impatient. Hence, the use for the function.)

Modifications of the Function in the Code

For the environment which I built the Arduino, the brightest measured light was below 1100 and the darkest was above 800. (Measured by photocell/LDR in the kit.) The longest I was able to wait for the lights to blink was 2000ms and the shortest blink was 100ms.

Therefore the modified formula is:

Of course, these variables might be different for you!