DIN rail single phase two wire LCD display energy meter

设计一个轨道交通自动售票电路，只接受1，2，5元人民币，每张票价定额5元，并支持找零。要求： （1）用状态机方法设计；(Design an automatic rail transit ticketing circuit, accepting only 1, 2, 5 yuan, 5 yuan per ticket, and support change. Requirements: (1) design with state machine method;)