Module 1 – Relay between RFM12b and ThingSpeak

This post is part of a series on Arduino-based energy and climate monitoring.

This is the core of the network of Arduino’s that monitors various sensors in and around my house. It consists of an Arduino Uno with an Ethershield, connected over i2c to an Arduino pro mini. The pro mini is connected to an RFM12b board and receives data packets from each of the sensor modules.


The reason for splitting this over two Arduino’s is that both the Ethershield and RFM12b use SPI. The Ethershield (version 1) does not play nicely with another SPI module.


All other modules send their sensor data to this one using RFM12b. Since I don’t have wired ethernet available near the location of this central module, I resorted to a TP-Link WRT703N wifi router.


The TP-Link WRT703N is running OpenWRT and is configured as bridge between the wifi network and the wired network connection on the WRT703N. The Arduino Ethershield is wired to the WRT703N, and receives an IP address through DHCP.

Power is provided from a micro-USB phone charger to the WRT703N, which subsequently powers the Arduino Uno through USB, which subsequently powers the pro mini through two breadboard wires.

The sketch for the Arduino pro mini can be found here, the corresponding sketch for the Arduino Uno is here.

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