Thursday, May 20, 2010
The soil humidity sensors are really just two nails placed a certain distance apart in the soil. The Arduino senses an analog value based on the voltage drop from one nail to the other. Low resistance means more humidity in the soil, and thus a smaller voltage drop. Mr. Holt had a good idea to coat the tops of the nails, where the wires are soldered, so that they would both be protected and easily seen by anyone gardening. The readings from the soil have been amazingly consistent with our expectations of the soil dryness.
Posted by Steve Temple at 10:40 AM
Thursday, April 15, 2010
The students completed the final design and fabricated the solar tracking mechanism and sensor station. The station consists of a servo that swivels the panel and housing (black) along an axis concentric to the mounting pole (white). A limit switch was installed to make sure that the panel could be rotated back to a home position when the sun went down. The servo then turns the housing until the switch is pressed and then turns the servo off. The photocell, servo, limit switch, and pv panel wiring is fed down through the mounting pole and then into the sensor station. We installed it in the garden, and it seems to be working just fine. Some adjustments will need to be made because the wires inside the mechanism can sometimes get tangled in the servo motor, causing the solar panel not to return to a home position when the light level is low (night time).
Posted by Steve Temple at 10:28 AM
Monday, March 29, 2010
After having a group discussion about the strengths and weaknesses of every team's prototypes, we decided on fabricating two different designs and then testing to see which device would work best. One device uses a vertical axis to turn a cylindrical mounting for the solar panel, while the other design uses a gear/linkage to turn the panel along a horizontal axis. The teams went to work on the fabrication process and the designs are looking really good. Some students worked on the sensor station mounting board that will secure the micro-controller to the inside of the water proof casing. One student is also finalizing the software for the sensor stations which will include four humidity sensors, and the control routine for the solar tracker. We are getting very close to completion!
The components for powering the irrigation system have all arrived (panels, linear actuators, pillow blocks, charge controller, inverter). The tracking system, designed by one team, will consist of a linear actuator as opposed to a servo. The panels will be mounted on an axel that will swivel between two pillow blocks. The linear actuator will tilt the panels according to the same mechanism used in the sensor stations - two photocells with a small shade divider between them. We anticipate this system of panels will produce more energy than we currently need. That means we can use it to also possibly power a future lighting system and/or webcam for security and monitoring. Future plans also include a small greenhouse, aquaponics and more!
Posted by Steve Temple at 11:01 AM
Tuesday, March 9, 2010
Once the students had learned to sense the soil and sunlight for the garden irrigation system, they then began the work of designing a solar tracking system that would be hooked up to the micro-controller so that the entire system could be "off-grid". The students were broken into teams to design different prototypes for the solar tracker. The students are also in the process of learning how to control servos, so once they have the design, they will build the design and program the micro-controller to move the servo so that the solar panel tracks the sun's position. The students will then judge the designs of all the teams and a decision will be made to see which design makes the most sense. So far the designs are looking really good! Nice work teams.
Saturday, January 16, 2010
After a few months of learning some of the fundamentals of the Arduino micro-controller, and also learning some basic circuitry, the students began work on their first programming project: Make a program that senses the moisture, senses the incident light, and then turns on a green LED if the moisture level is ok, and the turns on a red LED if the moisture level is too dry, AND if the incident light is low - we want to turn on the drip system in low light. Many teams were able to write the program and finish the task quickly! Yahoo! The next step is for the students to learn how to send a wireless transmission as opposed to turning LED's on/off. Should be fun!
Posted by Steve Temple at 5:53 PM
The students cut all the pipe for the irrigation, and then hooked it all in to the plenum. They then buried the lines, and they are now ready to add the drip irrigation tubing and the emitters. The plenum is essentially a large tube with eight solenoid valves that feed off from the main line. We are concerned that there just won't be enough pressure in the line to get the valves to open and then more importantly, close again. We may have to either modify the valves, or add a pump to the irrigation system. We shall see...
Posted by Steve Temple at 5:40 PM