changing the value of led gray level
The gray level is a very important parameter . The gray level decides that colour is the main observation point.
of course, these value are not rigid and unchanging. we can adjust the output-value with two methods as follows:
*change the led currnetly:however diffient parameter led may be, we can change its gray level through adjust led  work currently.in general, max allowable continuous working current of led is 20 mA .
most of led was nonlinear and direct proportional to its operation,apart from red led has   saturation phenomenon occurring.
*pulse-width modulation wave(PWM): methods to generate pulse-width modulation wave with single-chip microprocessor to                      adjust that value of led gray level.A point to note is that cyclical of PWM should be short,  and frequency should be high. the all of the user do not look that led trembled slightly as led working. PWM are more geared to changing the value of led gray level.