How to connect the button battery led lamp beads?
LED under normal circumstances, long feet for the +, you can also use the multimeter.
First check the polarity of the LED pin: (LED it is a semiconductor diode device, so it has a one-way conductivity) to supply the LED voltage + pole connected to the LED + pole, the voltage - pole LED - pole.
The series resistance can be calculated as follows: R = (supply voltage - Vt) / 20, where Vt is the tube pressure drop.
