Relay module is single chip microcomputer to a low level, triode conduction, relay of absorption, triode is what? Relay on baidu such, relay (English name: relay) is a kind of electric control device, is that when the input (incentive) change to specified requirements, the output electric circuits of the accused in a predetermined amount of step change of a kind of electric equipment, it has a control system (also called input circuit) and control system (also called the output circuit), the interaction between usually used in automatic control circuit, it is actually with a small current to control large current operation of a kind of "automatic switch", so in a circuit plays an automatic adjustment, safety protection, conversion circuit, relay module exactly what role?