Automated Plant Growth System

Transcription

1 Automated Plant Growth System Douglas Cooper, Desmond Persaud, and Samael Reyna School of Electrical Engineering and Computer Science, University of Central Florida, Orlando, Florida, Abstract The main idea of this project is characterized by the ability to automatically measure and regulate the main growth characteristics of plants while requiring minimal user interaction. Project includes regulation of nutrient concentration, ph level, and volume of water in our system. System will also give feedback of CO2 level, humidity, and temperature. An automated lighting level adjustment will also be integrated into the project. A wireless interface hosted by a web-server, web-based GUI for system settings and viewing of environmental conditions and a database that will contain existing settings for common plant types as well as data logging purposes. Index Terms CAMAC, Data acquisition, Pulse width modulation, Stepper Motors, Wireless LAN I. INTRODUCTION The Automated Plant Growth System utilizes a hydroponic environment which offers a solution to automatically monitor and regulate basic and critical elements that will optimize growth of plants, as well as provide feedback for some of the conditions surrounding the plant. The portion of the system that is regulated includes nutrient consumption, ph balance and artificial lighting while the feedback portion is provided for Carbon Dioxide level, humidity and temperature. Because it is necessary to keep the growth environment periodically clean and fresh, a pump and valve system must be incorporated that will allow for two different configurations. The first configuration is through the use of large containers, one of which will be used to source the clean water and the other which will be used to drain the old solution. The second configuration will allow the user to connect a pressurized water system, such as municipal city water, as well as a drainage piping in order to reduce the amount of user interaction with the system. As lighting is the one of the most critical elements needed for plant growth much consideration has been made on how to approach this part of this system. In lieu of the going green idea, it was chosen that the lighting be LED based which will use much less power and last longer than typical indoor grow lights. Because LED lighting does not emanate with nearly as much heat as the traditional lighting sources, they can be placed much closer to the plants. With this idea in mind, the basis of the lighting system allows for the light to maintain a constant distance from the plant and self adjust as the plant grows. A wireless interface will be incorporated that can allow a user to locally interact with the system in a local network This will be accomplished by an on-board wireless server that will host a web page which acts as a GUI type user interface allowing the user to view the various conditions of the system as well as setup configuration the settings of the system. Additionally, the on-board server will host a database which will contain two types of information. The first will be a general database of common growth characteristics of various plant types so that a user may easily set up the system without a lot of knowledge of the plants that are being grown. Of course the more knowledgeable user will have the ability to define specific settings and add to the database if they so choose to. The second portion of the database will house the data logged information about the conditions of the system which can be viewed for historical analyses. A) ph Probe Figure 1: ph probe II. SENSORS A BNC ph probe that generates its own potential to measure was ideal for this project. The instrument takes measurements ranging the full scale from 0.00 to ph. The measurement accuracy is 0.01 ph. What the desired ph levels would be only require the knowledge of the tenth decimal place, and while it is very nice to know the ph to the hundredth decimal as listed on this unit, it will not be necessary.

2 The manufacturer specifications use the Steinhart-Hart approximation for temperature approximation. This approximation can be described by the equation below: where, T - Temperature in Kelvins A, B, C Coefficients R Measured Resistance. (1) Figure 2: ph output circuit The output of the BNC connector gave -420 mv to +420 mv to signify different ph levels. We used the circuit above to offset and amplify the signal to readings that our microcontroller can read. The BNC connector s noise is reduced by the input buffer, than offset to positive, than finally a gain is added to the system. B) Humidity and Temperature Sensor To provide feedback necessary for the user to maintain proper humidity in the area of growth, a humidity sensor will be included to provide accurate measurements of the plants surroundings. The coefficients described by this equation were taken from documentation provided by the manufacturer after their own regression testing. Assuming a maximum input voltage of 5 V, the desired maximum output is 5 V and a minimum of near 0 V. Because the output of the thermistor acts as a current source, a current-to-voltage converter was implemented in order to utilize the analog to digital converter. C) Liquid Level Sensor Determining liquid level of the solution helps ensure the necessary height of the solution for the plant s roots to gain access to water and critical nutrients, it also provides the information needed to precisely calculate the correct ratios of ph and nutrient chemicals that must be added to the solution. Given that the horizontal surface area inside the feeder is constant, the height of the solution is the only component necessary to make these accurate volumetric calculations Figure 3: Temperature and Humidity probe The unit that was used required a simple circuit which is shown below. It gives a pulse width modulated output to the microprocessor which does not need any conversion for the humidity portion of this sensor. 10K PWM out (Humidity) 5VDC Vout (Temp) Figure 5: Pressure sensor diagram Figure 4: Temperature and Humidity circuit The approach used for this application is the pressure sensing approach. The specific component chosen is a MPXM2010GS pressure sensor made by Freescale Semiconductor. This sensor also provides on board temperature compensation and self calibration, as well as a linear output.

3 Description Pressure Range Max Supply Voltage Typical Supply Voltage Max.Output Differential Voltage Table 1: Pressure Sensor Specifications Specification 0 10 kpa 10 VDC 5 VDC 25 mv The output of the sensor is a differential output which provides a maximum difference of 25 mv given a supply voltage of 10 VDC. A) Microcontroller III. SYSTEM INTERFACE AND CONTROL The system utilizes two microcontrollers, an ATmega 168 and 328P, to process the sensors and regulate the motors and lighting system. The microcontrollers have multiple analog to digital conversion inputs for some of the sensors and pulse width modulated inputs for the humidity sensor. Since the sensors do not require any feedback from the microcontroller, they do not require any digital to analog conversion. The digital outs on the microcontrollers are used to regulate the motors for the pumps and lighting system. The microcontrollers is programmed with a C- based language in conjunction with a compiler and development board, created by Arduino, to process the higher level functions. The microcontrollers interface with the Lantronix Matchport b/g pro, which is a data server that hosts a user interface web page, through a UART connection on both chips. The diagram below shows the overall function of the system, where the microcontrollers interface with the sensors and regulators, and the website interfaces with the microcontroller to adjust environmental constraints and give feedback. Figure 6: Pressure Sensor Circuit As the BNC connector output before, this system had to have a similar circuit to offset the voltages as well as amplify the signal to its proper digital signal. D) Carbon Dioxide Sensor The sensor used in this project is a CO2 EngineTM (K30) NDIR type sensor developed by SenseAirTM. For this application, only the analog output OUT1 will be utilized which provides a measurement range of 0 to 2500 ppm. Since the output voltage is linear to the input voltage, an input voltage of 5V will be used which will provide a maximum output of 5 V. The following equation was derived using a maximum measurement of 2500 ppm and 5V input maximum:. (2) Using the analog to digital inputs on the microcontroller and the equation above the sensor is utilized in the system to give an accurate reading of CO 2. Figure 7: Block Diagram of System Interface B) Network and User Interface To reduce cost of the overall project the MatchPort b/g Pro was donated by Lantronix and is used in the system. The MatchPort b/g Pro is the gateway to the internet for our microcontroller. Due to the layout of the Universities internet network, the MatchPort will be utilized with an adhoc network. This solution to networking provides an on-chip data server with b/g capabilities which will host the web page. The serial interface on the microcontroller will interact with the Lantronix module through the web site. The web site is written using a java applet that opens the serial port and sends the data at the user s request. The MatchPort has an on-board data server to host the site.

4 Below is a block diagram of the network layout that is implemented in the system. Whenever a connection is made to the webpage, the user is actually connecting directly to the system. Using this layout is advantageous because only one connection is made and it simplifies the system while still allowing for wireless web access. This network layout eliminates the necessity of an external host for the web site and utilizes the full capabilities of the Lantronix module. The web page will allow the user to connect and edit certain environmental constraints controllable by the system. Currently the system can control the ph level, feeding times, liquid level, and lighting times and frequency of lighting. Figure 8: Block Diagram of Network Interface C) External Data Storage Since the microcontroller only has limited space for data storage of the code an external data storage device is required for data logging and database storage. The system uses the Secure Digital breakout board because of the commonality of the media, minimalistic pin usage on the microcontroller, and the cost effectiveness. The first function of the external data storage device is to store the data the microcontroller receives from the sensors. Each sensor will input its reading to the microcontroller and then will it will be stored onto the storage device. The capability of the Secure Digital card is that it is large enough to hold at least one day complete of data. Even though the system does not erase the card frequently there is extra room left on the card for more data depending on the size of the actual Secure Digital card being used. Currently a two gigabyte size Secure Digital card is being utilized in the system. A. Lighting IV. REGULATION The main idea behind the lighting system was to provide an unnatural light source that could sustain plant life and minimize power consumption as well as cost. Through research it was determined that LED lighting would best suit these requirements. Since the light source itself was not a design feature of the project, the focus was maintained on integration aspect of the project. The figure below shows the LED light chosen that is comprised of the blue and red spectrum, which are the necessary wavelengths of light required for proper plant growth. Figure 9: LED Light As part of the integration, two main features were implemented: the first was to allow for on and off cycles, which is required by the plant for proper growth, and the second was a motorized lifting system which maintains a constant distance between the plant and the light at all times. Through the use of a digital I/O pin on the microcontroller, the lighting is switched on and off with a relay. However, to minimize the current drawn from the microcontroller, a simple BJT circuit, as seen in the figure below, has been implemented to reduce the current drawn to about.5 ma. Figure 10: Light Cycling Circuit The lifting system utilizes three main components: an optical sensor, a contact sensor and a motor control circuit. The optical sensor, which is used to detect growth in the system, is an infrared proximity sensor which has been implemented through the use of a comparator circuit as seen in the figure below. This circuit will provide a signal to the microcontroller when an object has been detected within a fixed distance which is determined by the voltage divider connected to the comparator.

5 Figure 11: Optical Sensor Circuit The contact sensor is a magnetic reed switch which lets the system know when the plant has reached its maximum height in the system. The implementation of this sensor does not require any special circuitry except for a buffer on the input of the microcontroller as seen below. Vin = 5V Magnetic Sensor N.O. pin9 pin LM2902 (14-DIP) - + pin8vout Figure 13: DC Motor Control Circuit B. Feeding System Through the group s research on optimizing plant growth, it was decided that the main requirements for this portion of the project would be to regulate the nutrient content and the ph level of the solution. Because the chemicals used require fractions of a tablespoon to be added to the system it was necessary to find a manner in which to apply such small doses. The most effect method found to accomplish this was through the use of peristaltic pumps, which is a self priming mechanism that compresses the liquid inside tubing between small spaced pegs. The diagram below depicts such a mechanism. Figure 12: Contact Sensor Circuit The motor used to lift the lighting is a variable voltage car window motor which has been implemented such that the motor will move slow enough so as to not jerk the lighting during stopping and starting. The control of the motor was designed such that the motor could go in both forward and reverse directions through the design of an H- Bridge. The inputs seen in the circuit below are connected to general I/O pins on the microcontroller. Figure 14: Peristaltic Pump The pump was implemented using a stepper motor and a stepper motor control circuit. Since it was determined that only one pump would be on at any given time, a multiplexer controlled by I/O pins on the microcontroller would determine which one is selected. The control circuit itself is based on the L297/L298 application notes by

6 STMicroelectronics which allows for precision control over the motors. The circuit below shows the configuration of these to IC s along with L6210 which provides diode protection from kickback current from the motor. custom off the shelf ATX power supply was utilized which provided all the power needed by the various circuitry. Additionally, any AC power required also used custom off the shelf transformers in conjunction with a surge protected power strip connected to a standard 120 VAC outlet. The block diagram below outlines the configuration of the power distribution: 120 VAC ATX Power Supply 12,5 VDC12, 5, 3.3, -12 VDC Transformer 24 VAC Figure 15: Stepper Motor Control Circuit Relay Circuit Outlet Valve Control Circuitry Relay 24 VAC Inlet Valve Additionally, various pumps were added to the system for mixing and to control the flow of liquids all of which are controlled by a similar relay circuit as seen in Figure VAC Relays(x4) 120 VAC 120 VAC 120 VAC Figure 16: Power System Configuration Figure 16. Peristaltic Pump setup The image above shows a model of our three input peristaltic pumps. The multiplexer allows for only one to be turned on at a time which is good because there is no fuse in the system. The pumps should not be in a position where they might draw enough current to be harmful to themselves or the system. V. POWER SYSTEM This project required a dynamic range of power to be distributed throughout the system where components such as the lighting, valves and pumps required AC power and all others will require DC power. Since the focus of the project was devoted more to the controls and implementation of sensors, a unique power system was not designed from the ground up, but instead the use of a VI. STRUCTURE The overall design has been chosen to be a rectangular type structure which allows for the simplicity and the expansion that this type of system can offer, should it be necessary in the future. The structure itself would be holding both the electrical components and the various chemical solutions in single structure, without the need for anything to be mounted in a remote location. This structure has an initial stage of the water reservoir as well as the other chemical solutions being filled at each cycling period. The feeding pump should be located in the center of the tank because it maximizes the pumps output. Solution mixture will flow from the center of the tank, through a pipe upward and hopefully disperse evenly by calculating total rate of flow minus the effect that gravity has on our system. Tubing is equidistant from both the center output pipe and each plant allowing the liquid should be distributed evenly to each plant. After the solution goes up and through the roots of the plants, it

7 would flow back into where the rest of the solution is being held. It is for this reason that we would need to have exit valves to clear the used solution after about a week or two pending the size and type of plant that is used. A) Chemical Sensors The chemical sensors are in positions that would allow constant/on-demand measurements of the quantity of each in the solution. During feeding, the chemical make-up of the solution will change based on the amount of nutrients that the plant will consume. This feeding cycle, over time will reduce the amount of each chemical because the used, non-consumed portion is being put back into the solution reservoir. Once the quantities have reached a given a minimum threshold they would be replenished accordingly through the peristaltic pumps. B) Environmental Sensors Because the close proximity of the sensors with the actual plants themselves, it will not make much of a difference as to their physical position. For aesthetic purposes, it would be well placed on top of the electrical components and to the side of the plants. The sensors would include lighting, CO2, humidity and temperature. There are no intentions to try and adjust these parameters but are there for read only features to notify the user for climate changes and what effect that has on the plants. C) Liquid Level Sensor This sensor is placed directly above the actual tank holding the solution, where a tube is connected to the end of the sensor and directed down to the bottom of the tank. This sensor is remotely connected to its circuitry but not through a long distance. D) Lighting The circuitry and motor are all mounted on the very top of the structure. From this area the lighting sensor is connected via a cable and mounted to the light where it will move up and down with the light. The contact sensor will be connected to the bottom side of the top of the structure such that it can detect when the light has reached the maximum position. Figure 17: Structure Diagram E) Frame and Electronics Protection The frame will be sturdy enough to more than compensate for the fact that this entire unit will move more than a few times. There will be several liquids which need small portions to be added into our system which is to say that rigidity is essential in these portions of the frame. The electronics will be close to the liquids which makes any electrical engineer a little sensitive to the thought as to what might happen should there be a leak in the system. Currently there are no situations that are deemed critical enough as to move the entire electrical components away from the liquids. F) Piping The structure itself will require at least two different types of piping. The solution and the chemical components will have three different volumes and flow rates, requiring the difference in sizes of the tubing. While it may be possible to use the same size, it may not be as practical to dilute the chemicals so that the system has equal pipes flowing liquids throughout. In the feeding portion of the project, to allow for even water flow, the solutions pipes have been routed in such a fashion as to allow for even liquid dispersion. In the chemical regulation portion of the project, the chemical solution will require a smaller amount of liquid, possibly in the order of an eighth inch plastic tubing. It is these small measurements that caused us to consider solutions that have been used in the medical field for some time

8 now. The water regulation part will require a ¾ opening for reasonably fast fill and drain situations. G) Reservoirs The system has five reservoirs holding the ph up and down, Nutrients, water, and the mixture itself. Luckily three of these chemicals will only require minimal amounts to be added to our solution, something in the order of a teaspoon per gallon. It is very easily and inexpensive to acquire a liters worth of these chemicals possibly out living the actual plant itself. While it is to be taken into account the fact that there are multiple plants, and with each plant it will increase the consumption of the chemicals, it still almost seems negligible when looking at the entire system and the need to compensate for the changes per plant that it is going to have. The only thing that should be carefully watched is the fact that plants can get infected which can radically change the chemical solution. VII. CONCLUSION The main goal of this project was to build an automated system that can monitor and regulate environmental conditions for growing plants. Using strong research and foresight in the design of the system allowed the engineers to reach each of their requirements and goals in order to design a fully functional product. The microcontrollers that were used for this project are the ATmega168 and the ATmega328P microcontroller which were excellent due to their easy programming language and computing power. They were used in conjunction with the Lantronix MatchPort b/g Pro, which provided a wireless interface which can be used to connect to the system both locally and externally from the network. In addition, the system provides a data logging capability which is stored on a Secure Digital Card, and accessed using the web based user interface. The microcontrollers read in measurements from different sensors and regulate different devices that control the environmental growth factors for the plants. The sensors used include temperature, CO 2, Liquid Level, Humidity, Nutrient and a ph sensor. The system is able to adjust environmental conditions such as ph, feeding times and liquid level which are accomplished through the use of multiple homemade peristaltic pumps. A separate microcontroller is used for the lighting system because it is very intricate, so in order to simplify the code a separate microcontroller is used. The lighting system maintains a fixed height above the plant automatically as the plant grows and it also regulates day and night cycles. Additionally, the power system distributes the necessary power to each of the valves, regulators, microcontrollers, and sensors. ACKNOWLEDGEMENT The authors wish to acknowledge the assistance and support of Lantronix, Sunstone, and Senseair for their donations to this project. BIOGRAPHY Douglas A. Cooper is a senior Electrical Engineering student who will be graduating in August 2009, Magna cum Laude. Doug has held prior internships with the U.S. Army and Siemens Energy Inc. and is currently interning with the Navy. He plans to pursue his M.S.E.E. in Electro-Optics upon graduation while working for the Department of the Navy as a Systems Engineer. Desmond Persaud is a senior Computer Engineering and Molecular and Microbiology student who will be graduating with a duel degree in August Desmond is an intern with Lockheed Martin and will begin working there full-time upon graduation. He also plans to attain an M.S. in Computer Engineering with a focus in embedded systems programming following graduation. Samael N. Reyna is a senior Electrical Engineering student graduating fall of A Member of SHPE with certifications in the automotive industry for mobile electronics. Sam has interests in Human computer interaction in with an emphasis on Behavioral sciences. After graduation he plans to do independent study in voice recognition systems. REFERENCES [1] ATmega168 data sheet, Rev. 2545P AVR 02/2009 [2] Freescale Semiconductor MPX2010 application note, MPX2010 Rev 13, 10/2008 [3] Humirel HTF3000 application notes, HTF3000LF HPC077 Rev I April 2008 [4] Lantronix MatchPort b/g Pro integration guide, 2008 Lantronix. MatchPort b/g Pro [5] STMicroelectronics L297/L298 application note, 2001 STMicroelectronics