[Training Camp-Advanced Class] Internet of Things Socket

1. Introduction

1. Use Arduino programming to realize intelligent distribution network, mobile phone App control, and smart speaker voice control

2. Lichuang EDA designed the circuit, Fusion360 designed the shell and parts assembly, and KeyShot product rendering

3. ESP8266 is the main control, including a relay, a user button, an RGB indicator light, and a DS18B20 temperature sensor

2. Integrated AC-DC power module, used for system power supply, or USB interface for power supply, with two expansion pins reserved for external OLED, etc.

2. Hardware circuit analysis

1. Download circuit

①The USB-to-serial port chip uses CH340C, which has a built-in clock generator and does not require external crystals and oscillation capacitors.

②CH340 chip supports 5V power supply voltage or 3.3V power supply voltage.

When using a 5V working voltage, the VCC pin of the CH340 chip inputs an external 5V power supply, and

And the V3 pin should be connected to an external power supply decoupling capacitor with a capacity of 0.1uF. 5V operating voltage reference circuit:

When using 3.3V operating voltage, the V3 pin of the CH340 chip should be connected to the VCC pin

Connect to each other and input an external 3.3V power supply at the same time. 3.3V working voltage and automatic download reference circuit:

2. Relay drive circuit

Reference circuit:

The status of each pin during ESP8266 power-on (reference: Power-on pin initialization status problem ):

Analysis of the role of optocoupler:

The relay control pin is GPIO16, which is high level during power-on and uses light

coupling to prevent the relay from conducting during power-on, and then cooperate with the transistor to drive the relay

Diode function analysis:

When switching a relay, due to the self-inductance phenomenon, an inductive electric current will be generated on the relay coil.

**Potential, a diode is added to both ends of the relay coil to form a loop, so that the electromotive force generated by the coil is

It is consumed in the loop in the form of freewheeling current to protect the components in the circuit from being damaged.

3. AC-DC power module

The AC-DC power module uses Hailingke's HLK-PM01, 5V-3W output power, HLK-PM01 data sheet reference circuit:

Input components: Output components:

It should be noted that the withstand voltage derating of the filter capacitor of the output component is greater than 75%. If the output voltage is 5V, the withstand voltage of the filter capacitor should be greater than 20V.

3. Picture display

4. Debugging process

2020-8-17

1. The circuit board arrived today and has been soldered. No problems were found after downloading the test program.

2020-8-23

1. A bad ending is impossible