As a compliment to my previous project (TFT LCD clock), I decided to build another TFT/Arduino unit that would serve as a remote station. I could then make use of commonly available 433MHz RF xmt/rcv modules and wirelessly connect between the two units. I also wanted an excuse to experiment with these wireless devices by playing with antenna orientation, configuration (coiled vs straight), etc. to establish their maximum range and transmission accuracy. The base station located in another room of our home would transmit time information every few seconds which, in turn would be received by the remote station located in my ham shack (currently a spare bedroom).
The RF units (STX882/SRX882) were purchased from banggood.com for ~$3.00. Next, I located an excellent resource and code library focused on wireless interfaces (
RadioHead) and used their ASK (Amplitude Shift Key) drivers for my project. This type of modulation provides a simplified, one way channel for transmitting and receiving data with decent data integrity.
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| 433MHz Receiver and Transmitter Modules |
Each RF module connects to its respective Arduino unit via a single digital I/O pin. This allowed for easy initial checkout by directly hard wiring the transmitting Arduino to the receiving Arduino (ie. the RF interface was bypassed), then sending a test message. After ensuring message data was properly dis-assembled by the receive station, I removed the direct connection and plugged in the RF modules. It actually worked the first time!!! I did not check for maximum range but it works fine for the moment with a separation of ~50ft (from one end of our home to the other) so I am quite pleased. As shown in the following image, I also added support for an environmental sensor to display the room temperature:
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