HC-12 are cheap 433MHz wireless serial port communication modules with a range up to 1800m in open space. Each costs about $5 when bought from China, and 2 of them can create wireless UART link that can be used, for example, to transfer telemetry data from UAV. Or drive IoT device. Or connect sensors. Or whatever else one can think of.
It is based on SI4463 RF chip, has build in microcontroller, can be configured using AT commands and allows to use external antenna. Working frequency is divided into 100 channels starting from 433,4MHz up to 473,0MHz with 400kHz channel separation. Maximum output power is 100mW (20dBm) and receiver sensitivity differs from -117dBm to -100dBm, depending on transmission speed. It accepts 3,2V-5,5V power supply and can be used with 3.3V and 5V UART voltage devices (3.3V safe).
This project is a modification of my previous Bluetooth-enabled LED matrix display project, which used 8×64 monochromatic LED matrix (total 512 LEDs) for displaying scrolling text message. The original project used Bluetooth for display data transfer from a smartphone, but this one now uses Wifi. The display message is sent through web browser to a ESP8266 module that is configured as a web-server. No Arduino or any other microcontroller is used. ESP8266 alone works as a WiFi server and drives the MAX7219-based LED matrices.
You can well see it is an engineering sample, because I’m squeezing the wrong size packages into locations (quarter Watt resistors where eighth Watt components should be, etc) and using a mishmash of different component types, but you’ll forgive me, I’m sure.
The new design presents the Expressif ESP8266 device on an Arduino-sized board, supported by a full USB programming interface and power supply.
I should be careful to explain – this is not a “shield”. It does not sit on top of an Arduino. It REPLACES the Arduino. It IS the processor – and a whole bunch more…
In this article, you’ll learn how to build a system that can turn DC loads on and off using a mobile application. You’ll also learn how to perform this task via immediate actions or via timers set in advance for switching loads on and off.
You can implement this system in environments where you need to set your DC load for a specific time. This will allow you to use our Android application without any need for a hardware interface, keypad, and LCD screen.
This sort of touchpad speaks some special Apple mouse protocol. Luckily I found a code snippet on mikrocontroller.net which helped a great deal to get the thing going.
Then I used a standard AVR ATMega8 microcontroller to glue the transmitter and the touchpad together. That means, I poll the status/position change from the touchpad and if some swiping action was detected, the relative change of coordinates is sent via the radio.
I designed a compact double sided PCB housing both the microcontroller and the radio. It also features a 5V voltage regulator for the microcontroller and the power supply of the touchpad, as well as a 3.3V regulator for supplying the radio.
The touchpad is then connected to one of the free GPIO pins of the microcontroller which are accessible via dedicated pin headers