Experience in using light emitting diode with Single Chip Microcomputer

Forward saturation voltage drop of ordinary light emitting diode: 1.6 ~ 2.1 V, positive current 5 ~ 20mA

1) considering a problem, the working current usually takes the median value, iwork = (Imin + IMAX)/2. The reason for this value is that in order to prevent power supply voltage fluctuations, fluctuations within the permitted range can work normally.

2) The throttling resistance R = (VCC-v)/iwork, where V is the forward saturation pressure drop.

3) consider the irrigation current and pulling current that the microcontroller can withstand. If the single-chip microcomputer port is used as the driver, it must be pulled up. If it is not the driver port, there is no need to pull up.