Wireless Flex Node
The Wireless Flex Node is a wireless development board based on Arduino and the low power nRF24L01+ Transceiver. It also features a built-in high resolution temperature sensor and two selectable power inputs:
- 2.1 mm DC power jack (same as Arduino) with an input range of 4V to 15V
- Battery input that comes with a battery case for two AAA batteries
To get up and running quickly with the Wireless Flex Node is easy since their are video tutorials, example code, and open source libraries to help you easily start building wireless sensor networks. The example code shows you how to:
- Build a wireless mesh network
- Use power save features in the ATmega328p MCU and nRF24L01+ transceiver to achieve long battery life
- Make temperature readings
- Monitor battery voltage to detect when the battery needs to be changed
- Store setting in non-volatile EEPROM
The Wireless Flex Node even comes preloaded with the example code so you can use it right out of the box. Go to the "Additional Info" section below to access these resources.
The Wireless Flex Node comes equipped with the STTS751 Digital Temperature Sensor. The STTS751 can provide accurate readings with a supply voltage down to 2.25V to ensure you get the most life out of your battery. The STTS751 provides a temperature measurement resolution down to 0.25 degrees C.
The Wireless Flex Node runs the Arduino Pro Mini (3.3V supply and 8MHz clock) bootloader. Refer to the "Additional Info" section below for more information on powering the Wireless Flex Node from battery power and on programming it with the Arduino IDE. Other Wireless Flex Node features include:
- Female header pins to access unused digital and analog pins from the Arduino based microcontroller
- Solder and solderless prototyping areas to add additional sensors or other devices to the board
- Female header pins for programming the microcontroller from the Arduino IDE
- A power LED and user configurable LED connected to D7
- A user configurable switch connected to D8
The Wireless Flex Node base model has all SMD parts soldered on, but through hole parts are not soldered. This keeps the price low for those who don't mind doing through hole soldering ($9.95). To get the Wireless Flex Node with all parts soldered on adds $4. You can also include an nRF24L01+ transceiver module with your order for an additional $1.
Programming the Wireless Flex Node from the Arduino IDE You can use the Arduino IDE to program the Wireless Flex Node, but you must select "Pro Mini" with "3.3V and 8MHz" from the board menu. To program the Wireless Flex Node you will need a USB to FTDI board (sold on ForceTronics.com) or cable.
The Wireless Flex Node Design This board is meant to serve as a "node" in a wireless network. It is not meant to be the central device or coordinator in the network. Although it could be used for that purpose. You can also find example code for the network coordinator using the links below. Note that the example code is provided to help get you started on your own custom design. It is not meant to be a finished product.
Power the Wireless Flex Node from Battery Power The Wireless Flex Node has a battery voltage range of 3.6V to 2.25V. To save power and keep things simple there is no power conversion device between the battery input and board power or VCC. If you input more than 3.6V into the battery input you will damage the board. The limiting part on the low voltage side is the STTS751 temperature sensor. If you are not using the temperature sensor you can actually go down to 1.9V. Note that the example code shows how to monitor the battery voltage using the microcontroller so you can detect when the battery is bad. The Wireless Flex Node was designed to run off of two AAA batteries in series or two AA batteries in series (it comes with AAA battery holder). If you use the power saving features shown in the example code you can get a 1 year or more of battery life. You can use rechargeable batteries to power the design just make sure you stay within the voltage limits. Note that there is a jumper on the board that allows you to select either battery power or power from the DC power jack. If the battery power is selected the other power input is isolated from the design and vice versa. Note that the power LED is not used when battery power is selected to save battery life.
To access the open source libraries used to create a wireless network go to the follow GitHub link:
- RF24 library: https://github.com/TMRh20/RF24
- RF24Network library: https://github.com/TMRh20/RF24Network
To access the example code for this product go to the follow GitHub link: https://github.com/ForceTronics/nRF24L01_Wireless_Sensor_Dev_Board
The following is a 6 part video tutorial series on how this product was developed along with how to use it: