Teardown Smart Home WiFi Switch Module

2017-03-13 | By All About Circuits

License: See Original Project Switches

Courtesy of All About Circuits

Wi-Fi this, Wi-Fi that, Wi-Fi this and that! Everything is becoming connected to the internet with smart thermostats, clever baths, and now, intelligent toasters. In this teardown, we will look at a generic Wi-Fi switch that can be used to switch most high voltage (230V) devices.

The Outside

This Wi-Fi switch has two main ports, one for the incoming supply and the other for the outgoing supply. The switch also has a button on the top (on the right of the RoHS label) which is used for manual switching and setting changing.

The wire connectors

The impossible to break label!

The Main PCB

The main PCB shows a mixture of through hole and surface mount parts on the top side. Considering that the circuit simply switches a voltage upon receiving a request over Wi-Fi there it comes as no surprise that the PCB has few components. Capacitors, large power resistors and transformers are all components that one would expect to see in a high voltage switching device.  

The main PCB

One chip in particular that can be seen on the top side of the PCB is the PN25F08 which is an 8Megabit serial FLASH memory. This is most likely needed to store information regarding Wi-Fi networks, usernames, and other configuration memory that cannot be lost.

The PN25F08 Serial Flash IC

PCB Underside

The underside of the PCB shows all surface mount parts, the RF PCB antenna, and some heavily tinned traces. The extra tinning of the traces allows for more current conduction which is important when a load can potentially draw up to 10A (max rating of this Wi-Fi switch).

The underside of the Wi-Fi Switch

The power behind the Wi-Fi switch lies in the ESP8266 which is a very popular low cost Wi-Fi solution. It comes in many varieties and modules where it is most commonly found in the hobby market as the ESP01 module. The ESP8266 runs off a 3.3V line so we should be able to find a 3.3V regulator on the PCB somewhere. Considering the fact that this device is a cheap product the regulation will most likely be a linear regulator.

The ESP8266 Wi-Fi module

Further investigation shows that the 3.3V line is produced by an AMS1117 3.3V regulator. The AMS1117 is a small linear regulator that can provide up to 1A of current which makes it ideal in ESP8266 applications considering that the ES8266 needs up to 200mA of current during Wi-Fi communication.

The AMS1117 surface mount regulator

The circuit that controls the relay (ESP8266 and other needed components) requires power somehow. Luckily, the main input voltage can do just that! A small rectifier can be spotted on the far-right side of the PCB which appears to take the neutral and line conductors to create a rectified output. However, this would be unusual because of the presence of the transformer and in such a situation, the transformer would first step down the voltage from the mains to one that is more suitable which is then rectified and smoothed.

The rectifier and power handling components

Summary

Overall, the Wi-Fi switch shows how a simple ESP8266 can be used (with only a few components) to switch mains voltages. The switch itself is small and easy to use which only helps to encourage individuals to start connecting everyday appliances to the Internet Of Things. Since this module is so inexpensive, it has actually become a popular item to hack for electronics projects! You can see a diagram of its components below:

制造商零件编号 WRL-13678

RF TXRX MOD WIFI THTHROUGH HOLE

SparkFun Electronics

¥56.57

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