Sensor net makes life easier for rice farmers


Rice is cultivated all over the world in fields known as rice paddies and it is one of the most maintenance intensive crops to grow. The rice paddy itself requires a large part of that maintenance.

It is flooded with water that must be kept at a constant level, just below the height that would keep rice seedlings from growing but high enough to drown any weeds that would compete with the rice stalks for nutrients. This technique is called continuous flooding and a big part of the job of a rice farmer is to inspect the rice paddy every day to make sure the water levels are normal and there are no cracks or holes that could lead to water leakage.

This process is labor intensive, and the technology in use hasn’t changed much over the centuries. Most of the rice farmers in my area are elders with the approximate age of 65-70 years. For these hard working people a little bit of technology can make a big difference in their lives. This is the idea behind TechRice.

TechRice is a project that started as a collaboration between hackerfarm and Digital Garage in Japan. I was contacted by one of the heads of FutureLab, an internal R&D group inside Digital Garage and they were asking me about potentially interesting projects that could be done involving Internet of Things.

We met up with Digital Garage at their main office in Ebisu to discuss some possible projects. I also ended up talking about hackerfarm, a hackerspace some friends and I set up in rural Japan to focus on agricultural technology and issues that affect the Japanese countryside.

One project that came up was rice field monitoring using wireless sensor networks and it caught the attention of some of the members in FutureLab. That’s pretty much how the TechRice project started.

The area around hackerfarm is a hilly rice growing community with many stepped rice terraces. Because of the terrain, the rice paddies can’t grow to be more than a few square meters, approximately enough size to feed one family for a year. There can be as many as thirty rice paddies in one square kilometer, each belonging to different families that own and work them.

The rice paddies are not adjacent to the farmers’ homes so the farmers must travel to the entrance of the rice terrace every day and walk uphill to their rice paddy to inspect it. If there are any problems, they also need to do maintenance on it.

As the farmers age, going to the paddy everyday and making the uphill trek to their paddy becomes more difficult. As I discussed various problems in the local community, this stood out as a problem that can be solved with a bit of technical automation. The rough pieces to do this would be a water level sensor, a way to communicate that water level measurement to a server, and a way to visualize the data.

The main sensor node uses a device called “Saboten” meaning “cactus” in Japanese. It’s a device I designed originally for monitoring water levels in large water storage tanks in the Himalayas and also for monitoring mangrove forests in Costa Rica.

It consists of a modified Arduino platform based on the ATMega1284P microcontroller. I chose this MCU because it has 16kB of SRAM as opposed to the 2kB used in the standard Arduino MCUs. The RAM goes very quickly since we’re using a FAT32 file system to store data locally on an SD card, as well as assembling long text strings to send to the aggregator.

The SD card serves as a local backup for sensor data as well as maintaining a system log for debugging and analysis when the system has issues.

The main sensor is an ultrasonic acoustic range sensor called MaxSonar by MaxBotix.Acoustic sensors are often used in non-contact liquid level sensing because they don’t have the drawbacks that float or submersion sensors often suffer and won’t risk leaching chemicals into the water.

The MaxSonar is essentially an amplified acoustic speaker with a horn attached to focus the ultrasonic chirp in a single direction. We’re also experimenting with building our own ultrasonic level sensor using a waterproof piezo actuator and a 3-D printed horn to see what kind of range we can get.

For the rice paddy monitoring, we only need about two meters of range so anything around there would be fine. The MaxSonar has a range of around 10m which is overkill for this particular application.


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