The simplest circuit method of microcontroller pin controlling relay

fish001

The simplest circuit method of microcontroller pin controlling relay [Copy link]

First of all, we need to make it clear that the microcontroller cannot directly control the relay, whether it is a 3v relay or a 5v relay.

Reason: For example, the pins of the 51 microcontroller and the msp430 microcontroller cannot be directly connected to the relay. Although the voltage of the pin is sufficient, the coil that should be closed will not be closed due to insufficient current. A transistor needs to be added to amplify the current.

It is said to amplify the current, but in essence it is to use the pin as a switch to control the opening and closing of the real 3.3v voltage.

The figure below is a relay module that I designed in practice and can work normally.