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SMARTPLANTER

1. F 2 up TM50 Ce Ceri Co C4 TCP50 Co C4 to ti At the time that timer 50 is configured TM50 s count is Ce It then counts cycles from its configured clock source of Lo as Cei Co 2 and so on in a free running fashion until it overflows It then rolls over and continues counting from 0 and up At to when a rising edge is presented to the CPT5 input the TM50 count of Co is captured and latched into the capture register TCP50 On the subsequent rising edge at tj TM50 value is captured as C4 To obtain the frequency F or period T of the unknown signal presented at the CPT5 input the following applies assuming that C gt Co that is that TM50 has not overflowed since F 4 9152 MHz on the KORE9418 Tx 1 Fx 20 345 us Period T C Co Tx 20 345 C Co us Frequency of measured signal F 1 T This technique works as long as the dynamic range of F can be resolved with the chosen F and the 16 bit limitation of T50 F 2 has to be at least 2 times Fin but the higher the better and the better the resolution Unfortunately we have limited control on the timer s clock source since the capture function is limited to F 2 in any case as shown below this is more than adequate for the frequen
2. F EzIMN PERIANA IUAIS 47 The single layer printed circuit board implementation is shown next Soldering the smd voltage reference by hand was not funny The A D software Although the A D can operate continuously and can generate interrupts it is used in polled mode because this application does not require frequent measurements Measurements are taken on demand and the A D conversion complete flag 1s polled The following program measures the voltage on the solar cells under three distinct conditions 1 When the solar cell is open circuit The open circuit voltage can be used as a measure of solar irradiation This parameter 1s required in the evapotranspiration equations 2 When the solar cell is charging the battery This 1s used as a check that battery charging 1s actually taking place This voltage should be lower than the open circuit voltage 3 When the solar cell is charging the supercapacitors The supercapacitors present a load to the solar cell and this voltage 1s lower compared to the open circuit voltage 48 The program also measures the voltage on the battery and on the supercapacitors respectively The results are sent to the serial port It is interesting watch how these voltages vary when the battery and super capacitors are being charged Supercapacitors charge very quickly compared to the battery Their voltage approaches the solar cell voltage under load conditions in a matter of 20 to 30
3. compensate for conditions 2 and 3 only Condition 2 Configre Overflow lt T gt A A CPT5 INTP3 F 2 TI TM50 CoCer 65535 01 Co C4 TCP50 Co C4 to ti In condition 2 an overflow occurs before the first rising edge It is cleat that given the expected count range a second overflow cannot occur hence C gt Co All we have to do is clear the overflow flag 12 Condition 3 Configre lt T gt A CPT5 INTP3 T TMSO Cc Cori Co 65535 01 C4 TCP50 Co C4 to ti In condition 3 an overflow occurs between times tl and t0 as shown above The corrected
4. 4H 40 HE 7 Segment LCD Drive circuit The static mode drive circuit for this LCD is as simple as things can get as shown below It is a straight 1 1 connection of the S0 S27 signals to the LCD digit segments Pt d Digit 7 Segment LCD VOD 1 E 145 UL an 1 21 pl LOU 3 414 MOI 2 y 1525 UE 3 b paal d 23 au JL OM i H A JL OM 4 24 gala COMI HB 10 1 DOM3 Sd 3 23 414 pl F il pd 20 wild J 13 14 E a 2 it 2 peu p4 15 16 aaa or H 24 4E OM H 1 14 7 E 4 H 23 B m I I SA g 13 20 rj Pol aid 10 30 Es 59 11 31 12 JE On 13 7 513 pr gia 14 40 mir 14 34 El gd 1 2 514 FE 15 du quu 412 d 4 A qld JD Of 1B 36 qud 514 5 6 4815 A25 17 3r 4n H15 fi H ali pd 1H 33 B1B g 1l r EE ad 19 3H au 11 12 4321 4522 20 33 add 13 14 d 523 p24 15 16 428 GIG un 1H ET pie 4d ADO 13 20 Ag QAVREF UD Lt r c1 7 zy Pou 29 The LCD is mounted on a plug in board to the KORE9418 On the same board is mounted the debug LED driven by P5 0 The BIAS pin connection for the static drive mode The BIAS pin is connected as follows and as suggested in the upd78F9418 user manual LIPSO Woo co Below 1s the printed circuit board layout for the LCD plug in board to the KORE9418 Routing those 28 segment signals onto a kitchen made single layer printed circuit board was not easy and I ended up with 15 jumpers The result is shown below 30 LCD Driver Software Here is a program that shows how the LCD 1s driven in software It displays t
5. The SmartPlanter is designed to be autonomous in the sense that it does not require an AC power source to operate Power safety regulations are costly to gain certification for and besides it seems too cumbersome to have each planter connected to the mains 120 VAC supply I could have used a mains step down transformer or adapter to feed a low level DC power supply to each planter but then again the wiring would make it look unsightly and would reduce the mobility of the planter Hence the SmartPlanter somehow had to be self powered The only obvious option is to use batteries but having to replace batteries frequently is a pain Fortunately one of the features of the upd78F9418 is its ability to switch to a lower rate clock to conserve power but still the SmartPlanter needs to operate a water pump and this takes enough power to drain a battery in a relatively short amount of time The idea used here is to complement the power requirement using solar panels It makes sense to use solar panels in this application because plants cannot survive without sunshine Wherever there are plants there is bound to have at the very least some solar energy Even if the SmartPlanter is installed indoors it would be located in a place where the plant receives at least a few hours of sunshine every day even if it is diffused and not direct sunlight It therefore makes sense to use a solar panel to power the SmartPlanter but the planter should not rely complete
6. are already implemented in the design The Intended Use column shows functions I based my design around but ran out of time to actually implement them 18 CHAPTER IV COMPREHENSIVE BLOCK DIAGRAM OF ALL MAJOR FUNCTIONSAND CONNECTIONS System diagram S2 m i an S7 S8 gg MS E2 LS V2 19 Description of system diagram Water storage Vessels V1 and V2 form a water storage container of a few gallons The container is covered with a lid to reduce water evaporation Water refill discharge and drainage CAP gives access to fill the container and DIS 1s a discharge valve used to drain water out for maintenance V1 and V2 are inter connected by drain pipe P5 allowing water seeping through the plant soil contained in V1 to evacuate A tray 1s optional on the outside especially for indoor plants to keep drain water contained Enclosures Within the V1 V2 container are three separate enclosures El Actuators E2 Controller and E3 Fertilizer storage respectively Actuators El contains the watering and fertilizing actuators Fertilizing 1s done by mixing controlled amounts of fertilizers in with the watering system Watering is through magnetically coupled pump P operated by motor M1 Fertilizer storage and mixing Liquid fertilizer 1s stored 1n enclosure E3 and is refilled through access cap F Fertilizing is controlled by pinch val
7. connected in parallel These supercapacitors are charged by the solar cells They are then used to drive the watering pump The battery only supplies power to the microcontroller The software controls whether the solar panels charge the batteries or the supercapacitors when sunlight is available The software performs power cycling evenly distributing the solar energy to charge the batteries and the supercapacitors In this design the combination of the following features help make the SmartPlanter completely autonomous e Power cycling solar energy to the battery and supercapacitors e Using the supercapacitors to power the higher current devices such as the watering pump e Using the battery only to power the microcontroller e Using the power saving features of the microcontroller and switching between the high speed 4 9152 MHz and 32 KHz clocks 39 e Using the built in AD converter to measure voltages and make decisions based on the readings All voltages are measured solar cell voltage when open circuit solar cell voltage when charging the battery solar cell voltage when charging the supercapacitor supercapacitor voltage battery voltage microcontroller VDD voltage A block diagram of the SmartPlanter power section 1s shown below Solar Cells oO T Rechargeable Battery Low Dropout Voltage Regulator MicroController To gt SuperCapacitors W
8. minimum maximum and daily temperatures humidity and dew point and wind speed Atmospheric pressure can be estimated as a function of altitude which can be derived from geographical location Wind speeds can be assumed constant for indoor plants and being within a certain range for outdoor plants This project and the printed circuit board make the assumption that temperature humidity and dew point measurements are to be made using the SHT11 humidity and temperature sensor from Sensirion The PCB traces and circuit diagrams allocate a CLK and DATA signal to a header to drive a SHT11 device The upd78F9418 synchronous serial port mode does not work with this device because the latter is somewhat non standard The software has been tested on the DS92C420 but time did not permit to actually integrate 1t within this application Plant moisture control is a slow process I thought that it would be difficult to see visible effects on the short run It would take days of observation to see what the SmartPlanter 1s doing and actual statistical field trials are still to be done to characterize plant species and develop recipes that 1s watering fertilizing schedules for them This work 1s likely to be a long process that is beginning this year I therefore realized that it would be difficult to judge hence my submission essentially shows how I intend to use the features of the upd78F9418 to achieve these goals My submission therefore attempts to demonstrate th
9. performance even as an early prototype but there is still some room for improvement It is low cost completely submersible chemical resistant and works from a mere 4 cm of solar cell I would appreciate that its design be kept low key and that it not be reverse engineered The measurement of moisture using Gypsum blocks is another topic that took considerable research and I am still working on calibration techniques Whatever information is included in this submission is to be considered a work in progress The topic of Evapotranspiration ET its adaptation and application for this particular use represents a considerable investment in IP For this reason at the 11 hour and upon recommendation I choose to actually not present this as part of the solution I hand planned to include it as part of the project in the form of a compiled library but finally refrained from doing so In principle this should not affect the perceived usefulness of the the SmartPlanter and should be considered a refinement The moisture sensor tells the SmartPlanter that the soil is getting dry and it needs to water It is the ET equations that tell the SmartPlanter how much water to dispense based on estimates of how much water was lost the day before Well this part 1s simply not included for reasons outlined above This means that the SmartPlanter in its current state waters fixed amounts To estimate ET several parameters are required namely the atmospheric pressure the
10. purpose Several automated watering devices are on the market today but most of the affordable ones are open loop devices They feed water to plants with no knowledge of how much water 1s currently required by the plant or how much watering took place uy Water required Water supplied Plant Open loop systems tend to over water or under water resulting in reduced plant growth and health Over watering causes e Root rot Encourages fungus growth Under watering causes e Wilting amp shock There are occasions when it is desirable to maintain optimal plant growth and health such as in high priced horticulture and then a closed loop system is often preferred A closed loop system predicts how much water plants require and measures the effects of watering correcting itself to improve future predictions Closed loop Plants loose water through two main processes e Evaporation at the soil surface e Transpiration of the plant itself through its foliage The term evapotranspiration ET is often used to describe the combined effect ET represents the water lost by a plant Replenishing the lost amount through watering offsets the effect and keeps the plant under optimum conditions A mathematical model for ET was developed by Penman in 1965 It was subsequently simplified to what is known as the FAO 56 Penman Monteith equation The model still requires several measured parameters
11. seconds This program does not use the analog input board described above for it was written prior to the latter being constructed The only difference 1s that in this case AVREF VDD AVDD VDD VDD 5V code removed for publication The header files used above are IO h I use macros for simple things as configuring ports and toggling their outputs These do not warrant the code space used by making these functions and they run faster code removed for publication AD h follows code removed for publication AD c code removed for publication Here 1s a more elaborate program that displays the results on the measurements on the LCD using a combination of alphabetic whenever possible and numeric characters This program uses the analog input board printed circuit board The difference is that AVREF 2 5V the gain potential divider is still 2 0 code removed for publication 90 This program displays the following on the LCD LCD Display SOLO SOLC SOLB SCAP BATT FERL AI05 Voltage source Description Solar cell open circuit Solar cell charging supercapacitor Solar cell charging battery Battery Fertilizer level Voltage on AINOS spare ATO6 Voltage on AIN06 spare Time of day YEAR Year 8888 LCD segment test pattern 91 The alarm buzzer software I used the following circuit to drive a piezoelectric buzzer to serve as an audible alarm to raise the alert when the water
12. I to COMG signals can be used individually to drive the decimal points and colon symbols on a regular 4 digit LCD 33 The following circuit will adequately do the trick SEA COMI PXY 2 ud F4 8B Ya COMI Pxor F4 8B va COMI 3 3 ELN ABN Assume that PX Y PX Y 2 are port outputs Pull ups may be required This one 1s even simpler and uses less PCB traces but places a larger fan out requirement on the COM signals COMX J DP PXY 3 DP PRY 3 ELN PXY 2 34 I did not implement this trick on the LCD plug in board the first time around when I had the chance I regret this decision now Texas Instruments makes single three input exclusive or gates in a small outline package They operate down to 3 V This is the SN74LVC1G386 If time permits I will at least implement a single decimal point as a tucked on wire wrapped piece of glue logic I have developed a craving for decimal points 39 COMX a val la i j Agee PMH 4 EL AL A 8BIN I did not implement this trick on the LCD plug in board the first time around when I had the chance I regret this decision now Texas Instruments makes single three input exclusive or gates in a small outline package They operate down to 3 V This 1s the SN74LVC1G386 If time permits I will at least implement a single decimal point as a tucked on wire wrapped piece of glue logic I have developed a craving for decimal points 36 The power section
13. O b LL 16 bit timer counter 50 TM BO CPTS P27 a Edge 16 bit capture 16 bit counter INTP3 detector register 50 TCP5Q read buffer Internal bus The gypsum sensor resistance to frequency circuit s output is connected to the 16 bit timer T50 capture input CPT5 The edge detector on the CPTS5 input is configured to trigger a capture on rising edges T50 s clock source selector CPT501 CPT50 is configured to use 2 as the clock source driving the 16 bit counter TM50 The capture Selector tula i function does not work at the higher clock rate options In this configuration the T50 counter is free running and increments its count by one every 1 2 seconds Whenever a rising edge is detected on CPTS the current 16 bit counter value TM50 is captured and latched in the capture register TCP50 Note that the sensor s frequency output 1s also connected to the INTP3 interrupt To measure a pulse train frequency one simply has to measure the time elapsed between two subsequent edges of the pulse train period using an accurate and known time base as reference In this case the Lo provides time base source where f originates from an external 4 9152 MHz crystal Configre lt T gt A A CPTS INTP3
14. PNP transistor controlled by a port This approach turned out to be overkill since the low power CMOS version of the LM555 the TLC55 was being used The TLC555 draws a few micro amps when it is not driving a load Instead the RESET input controlled from a port is used to start interrupt the pulses to the gypsum block sensor It is critical not to keep the sensor continuously energized because of galvanometric effects 13 The final moisture sensing circuit used 1s as shown below Gr R1 3390 0 1 uF Caramic A2 2 Gypsum Black Sansor X2 1 M 1 1 AX1 2 21 3 cot Dao X1 4 0 1 UF Ceramic C1 0 1 UF Matal Film GND 14 Moisture measurement software The following program takes moisture measurements every 10 seconds and sends the results to the serial port for logging and graphing Accent 1s placed on moisture measurement aspects code removed for publicatoin 15 CHAPTER II DESIGN CONSIDERATIONS The SmartPlanter should primarily be solar powered and use a battery for back up purposes The SmartPlanter should be low cost problem free and easy to operate It should use as many features of the NEC upd78F9418 as possible 16 CHAPTER III SPECIFIC FUNCTIONS USED IN THE MICRO CONTROLLIER Hardware function usage Below 1s a block diagram of the updPD78F418 The table that follow show what features of the microcontroller are used in this application TIVPDA Bbi timer TH P25 Posi 2 Pet to Par TOU
15. S Bbi mee 02 pe ee Tos20 bons Pao tora 16 bit imer 50 amp K gt CPTSP2T Watch mer Wotchdeg timar KS SCHICK SCITxD P m i E AHFKXTS D Ah P54 ANAP 10 s AM TOS AD commenter fu AW zn AV am A E KROFPO to ASPAS CP TOUT iP Were Va hE Wm Wen wired 17 Actual Use Intended Use 8 bit timer event counter 00 Used for accurate delays Bin NN aE pump in PWM mode ome aie drive the buzzer tones oem Pe output of the moisture sensor A AA calendar BB UE dl crashes BEN LUE E NNNM computer namely LCD controller driver Used to drive a 4 digit 7 segment LCD display in static mode Pot0 J Usedto drive the keypad Pp Port o P2OSCK 0 O P21SOTXD J RSQ transmit P22S RXD 3 RSe32reeve P23CMPTOUTOTO Used to drive the buzzer 0 0 Y P2 4 INTPO TIO Used to enable disable the moisture sensor P25INTPHTH SHTMDATA O PA2eINTPJTOS 0 o SHTMEN O PA7INTPSCPT5 J SHTMCLK O Port 4 Used to control actuators AA Used to control actuators A e e voltages Pot8 UsedtodriveLCDdisplay ________ TS Used to drive LCD display Comparator ooo Tosense solar power level p p The Actual Use column in the above table represents the functions that
16. SMARIPLANTER A white paper submitted in fulfillment of the contest requirements for the Cornelius van D rebbel s Mad D esign Contest Hardware Submission K O RE9814 Co Sponsored by NEC Electronics America amp EDN Magazine Submission D ate January 5 2005 by Alain d Espaignet INTRODUCTION This paper presents a practical application of the NEC KORE9148 hardware kit in the implementation of an automated plant care system Heretofore called the SmartPlanter it is a closed loop system that measures and controls parameters essential to keeping plants healthy It uses a simplified evapotranspiration ET model based on the FAO 56 Penman Monteith equation and physical measurements to estimate the watering frequency and duration required to replenish water losses and then used to actuate a watering pump The SmartPlanter keeps plants healthy and fertilized at markedly reduced maintenance Actual soil moisture measurement closes the control loop and 1s used to continuously improve the ET model Seasonal model adjustments are made based on a real time clock calendar Configuration and status 1s through a keypad LCD user interface Low water supply level activates audible and visible alarms Solar power keeps a Lilon battery charged storing energy to operate fertilizer dosing and watering actuators Low maintenance with improved plant health growth is achieved through a unique combination of software and hardware Application description and
17. ater pump Fertilizer Valve Alarm Buzzer The circuitry implementing the above block diagram 1s shown below 40 Jp atis ty qiHFF l yoo pna des WIN 1 WoT E zb n L3 una woti NES AL saw 1B zi ann E m a d a o Pag m z IL pih a o eu ann yioo PEAT ELE E JD piat pun ah m f 2 polar Panel Py Int ysuL 4 I z Paola Eh IEE RD Jha af E GAO Ono Po AP AHO Mun a pape Eh t nn j APS dL later Pain Motor This circuit is implemented as a single layer printed circuit board which 1s a plug in addition to the KORE9418 It picks up the following signals from the KORE9418 connector P66 AIN6 44 1 2 4 P65 AIN5 P64 AIN4 43 3 4 44 P63 AIN3 P62 AIN2 45 5 6 AE P61 AIN1 P60 AIND CMPINO 47 7 z 4 AVSS P27INTP3 CPT 49 9 10 5 P26 NTP2 TO5 P25 NTP1 TI4 54 NE P24AINTPO TIO P23 CMPTOUTQ TC 13 i4 A P22 SI RXD P21 SO TXD 15 16 S P20 SCKIASCK P53 57 17 i8 58 P52 P51 Lg 19 20 50 P50 P3 The following circuitry also fits on this Power Section board 41 Alarm Buzzer circuit A high efficiency piezoelectric buzzer driver circuit is powered from the supercapacitor and driven by the T02 output Timer 02 1s the only timer that 1s capable of generating square waves of programmed frequencies with zero software overhead that 1s all using the internal hardware It was chosen to drive the buzzer for this reason It uses the 32 KHz external crystal because it is
18. cies being measured As a sanity check assume that the expected frequency range of the signal to be measured is between 28 Hz and 1 3 KHz as observed in preliminary tests The highest timer 50 count occurs at the lowest frequency This count should not exceed the maximum count possible with 16 bits i e 2 1 or 65535 At 28 Hz T 0 035714 seconds which is equivalent to a count of pulses of T T 1755 which is less than 65535 11 similarly the lowest timer 50 count occurs at the highest frequency of 1 3 KHz In this case T Tx 37 counts Hence it clear that it 1s feasible to measure soil tension by indirectly measuring the sensor s period T The resolution in the sensor s period measurement 1s 20 345 us The stability of the measurements is dependent on that of the external crystal Other variations in measurements are due to the temperature dependence of the timing capacitors used in the measuring circuit Special cases All 1s fine except for one complication Timer 50 may overflow and one can no longer assume that C gt Co Fortunately this condition can be detected using the overflow register TOFS0 Three conditions may arise 1 TM50 overflows both before time ty and t 2 TM50 overflows once before to 3 TM50 overflows once after t but before t With the knowledge that the expected frequency range of the sensor is between 28 Hz and 1 3 KHz it 1s clear that condition 1 should never occur This leaves us with having to
19. count 1s thus 65535 Co C and not C Co as in the absence of any overflows We note that an overflow condition occurred account for it 1n calculations and clear the overflow flag The software implementation of the above technique relies on the use of the INTP3 interrupt to detect edges from the pulse train to be measured A port is also used to turn the sensor circuit on and off The sensor circuit 1s kept off at all times to keep power consumption low It is turned on only when measurements are to be taken It is possible to excite the sensor with exactly two s s periods two rising edges of the bipolar waveform This 1s achieved by counting the edges detected on INTP3 and turning the measuring circuit off immediately after the second detected rising edge Preamble Bd Measurement gt lt Result A A A Experience has shown that it is best to actually let the moisture measuring circuit run for a few cycles to let it stabilize before taking measurements The duration of the preamble time should be greater than the maximum expected period of the signal Two edges are detected to take measurements of Co and C4 On the third detected edge Co C 1s adjusted for any overflows from which the final result can be calculated from knowledge of Fx To conserve power the supply to the moisture measuring circuit was initially fed through a
20. cter received until an end of message character 1s received at which point it may signal to the main loop the arrival of a complete message and its type by simply making an entry in the message queue In this way the main code 1s not littered with serial communications related variables and handles things at a slightly higher level This message queue technique 1s used in the SmartPlanter code to implement state changes and direct the main loop to specific state processing code sections in a clean and readable way 26 T he serial port This application does not really call for a serial port However the latter proved invaluable for debugging For those who are interested in studying the behavior of plant species it is advantageous to have the capability to log data to a host computer The serial port 1s meant to be an optional feature for those that require it In the final product 1dea that this prototype represents this optional feature is meant to be complemented with adequate host software The software should provide the ability to send specific commands to the planter to request and or set parameter values and for logging and graphing measurements The serial port on the upd78F9418 is easy to use Unlike the 8051 family of microcontrollers it uses a dedicated baud rate generator clock instead of reusing generic timers This makes configuring and using it less complicated The serial port is used in a number of programs presented here They a
21. e gypsum blocks provides information about the suction pressure in the surrounding soil The measured AC resistance varies as a function of temperature but equations do exist to compensate of the effect of temperature dependence G ypsum block soil moisture measurement To measure soil moisture using a gypsum block one has to measures the AC resistance between the block s electrodes Applying DC currents to gypsum blocks causes gasses to form at the electrodes hence an AC free of any DC bias current 1s required The requirements are that the block should be excited with an AC voltage source of around IV peak to peak Care should be taken not to maintain this driving voltage for long periods of time Short bursts of bipolar voltage pulses of a few volts in amplitude should suffice to give accurate and repeatable readings There are many ways in which these requirements can be met but the simple circuit below 1s the most economical and uses very little power ca R1 3390 a 0 1 uF Caramirt A 7 gypsum Block Sansor X2 1 X1 1 X1 2 4 3 MERI 0 1 UF Caramic 0 1 UF Matal Film GND In the circuit above the gypsum block sensor s resistance 1s part of an RC timing network As the resistance of the gypsum block varies with soil tension the output frequency of the circuit varies The output of this circuit 1s a square wave with frequency proportional to the block s resistance and hence to the soil tension Experiments have shown tha
22. easured and controlled by the SmartPlanter for this reason a host interface is essential Provision for this is made by the addition of an RS232 interface This circuitry is optional but provides the ability to perform data logging i Li 5232 OBS 4 PA F SOX 41 P215 0A K0 TN TOUT EN X2 Im I D3 Kad 22iSlRxD yet 4 RIDUT RAIN AI 3 4 SN A3 h EM INVALID X1 5 m Ad f d FORCEOFF ee 1 3 13 FORCEON emX3 3 MAX3221EUE SHO GND The jumpers on the RS232 level side are used to correct any TXD RXD mismatch according to the host interface connector used The jumpers on the logic level side are to facilitate the SmartPlanter s software development When it is connected to the M Station these jumpers should be removed so as not to interfere with the M Station signals The MAX32221 operates at 3 V and has a power saving built in feature When it senses that there are no RS232 level signals present on its input it automatically shuts itself down to conserve power It is planned that this interface will be connected in future to one of several other interface types namely e IrDA e USB using an RS232 to USB converter e RF Transceiver for a remote wireless interface 43 Here 1s the printed circuit board implementation of the above circuitry all handcrafted in the kitchen sink Cr D 1 The headers on the right hand side of the board are the voltage sensing headers and feed into the analog signal proce
23. for the computation of ET and generally would use data from a weather station In this implementation some assumptions are made by categorizing the plant s micro climate to simplify terms of the equation The simplified model uses only the following measurements solar irradiation humidity temperature and dew point To compensate for soil type variations plant type and other unknown factors the SmartPlanter uses a feedback loop to make corrections to the model The SmartPlanter is based on the NEC MCU to perform the following main functions Measures the following Humidity Temperature Dew point and Solar irradiation These measurements are used to estimate the EvapoTranspiration ET The ET estimate 1s used to control the watering duration and hence the amount of water dispensed to the plant Water required Estimated Water supplied Controlled The system also measures Soil Moisture to verify and correct the ET model The SmartPlanter functions primarily as a moisture controller Other functions include monitoring and controlling nutrients and logging data for analysis SOIL MOISTURE MEASUREMENT There are many techniques used to measure soil moisture To keep the SmartPlanter affordable the granular matrix sensor technique is used The most affordable form of such sensors is the Gypsum block Gypsum blocks have been used in soil science for 50 years Bouyoucos 1965 to estimate soil moisture and their performance 1s well documented Gy
24. he 3 6 V batteries because they will run it dry too early Examining the circuitry found in ZipZap RC cars closely gave me the answer supercapacitors 30 Supercapacitors Supercapacitors are high value capacitance capacitors Capacitance values are in the range of 1F to 10F and recently I have seen some in the 100F range in EDN These capacitors are amazing in the fact that they can achieve such high capacitance values in such small sizes They have limited voltage ratings however and care must be taken in selecting them although they can sustain momentary overvoltages The most common types are found in the 2 5 V range with others in the 5 5 V range I picked a supercapacitor with a 5 5 V rating to match the solar panels What makes supercapacitors more attractive than batteries when short bursts of high current are required is the fact that they have very low equivalent series resistances ESR of the order of milli ohms They can generally deliver much higher currents than batteries of similar size can deliver The other interesting aspect is that they can be recharged in a matter of seconds and not hours like batteries and in addition they have extremely long life for they can be charged and discharged practically indefinitely for they have no memory effect like rechargeable batteries All in all it is the perfect choice to power a watering pump In this design two supercapacitors of the Maxcap type of 0 47 F and rated at 5 5 V are used
25. he date the time and the year It repeats this cycle every 10 seconds code removed for publication 31 The LCD display module is shown next code removed for publication Here is a simple electronic trick to have the full 4 digits in static mode while still being able to drive the decimal point and the colon symbol This trick 1s based on the fact that an exclusive or gate can be used as a controlled inverter Below is the truth table for a two input exclusive or gate The truth table for the exclusive or logic function is easy to remember Whenever the inputs are different the output is a otherwise it is a 0 Now look at it slightly differently in two separate groups 32 Non inverting group Regarding the A input as a control input observe that when A 0 the output follows B Inverting group Again regarding the A input as a control input when A 1 the output 1s the inverse of Thus an exclusive or gate can be used as a controlled inverter Simply regard the one input as the control input When it s a 0 the output is non inverting When it is a 1 the output 1s the inversion of the other variable input This property of the exclusive or gate can be put to good use to fake out additional segment signals from the COMO to COM3 signals in the static mode In the static mode all the COM signals are the same A single COM signal can be used to drive the LCD backplane common signal whereas the COM
26. intended to be generating audible signals in the hundred of Hertz to low kilo Hertz range This audible alarm is used to raise a low water level alarm A piezoelectric buzzer was chosen because of its low current consumption Experiments have shown that even with just above a volt charged on the supercapacitor the buzzer can go on making a noise for quite a long time This is exactly what is required in this application Since water 1s crucial for the survival of the plant the SmartPlanter makes an annoying noise to attract attention when it senses that the water level is reaching dangerously low levels The buzzer is also used to provide audible feedback when a keypad key 1s pressed ICAP Buzzsr P 23 CMPTOUTOT O mG Fic hl 2P Polsturs Ssngar DD EB 4HMNTPAaTTIU B2ZHMNTPAICPTS AD 4 sins atur s Humidity Serigar DO AUD PLANTEA ITH PIBINTP2TOS Moisture sensor interface Below the buzzer driver circuitry 1s the header feeding the signals to the moisture sensor measuring circuit This sensor is crucial to the operation of the SmartPlanter 42 Temperature and Humidity sensor interface Following this 1s a header feeding the signals driving the SHT11 a humidity and temperature sensor This circuitry is optional and only used if evapotranspiration estimates are to be performed and used RS232 In addition for research purposes it is highly desirable to provide the ability for one to log the variables m
27. ints in the static mode I dropped the use of the decimal points in favor of more digits As I worked with the display the lack of decimal points became more and more unnerving and eventually I resorted to an electronic trick to drive decimal points and the colon symbol from other ports This trick only works in the static mode letting me have 4 full 7 segment digits and the decimal points and colon symbol for the time display The Seiko T392001 available from www eio com is the 7 segment LCD I chose to use Although it is an undocumented part and all that is available is the pin out information I implied that it would work using the static drive technique because it has a single common backplane signal COM I took a chance that 1t would work at 3 V and it did Actually this LCD turned out to be a better deal than it appeared for the price The display contrast 1s high and the viewing angle very accommodating I even got it to display some alphabetic characters whenever it could be done so that the result 1s recognizable as an alphanumeric character but sorry no X s V s or W s are possible o mmor SRE El 2 Nt EE co d NC Bd 46 4 AYE e4 3B a IE Pa d amp 1D Po JF IC ef 3G amp IPI BH CLH 9 E B EB 10 en 30 EA 11 25 al gF le Dru ae B 14 3E 43 NE 14 3D J4 18 la 3L da l 16 DPS ao IF 17 4E af 16 1B 40 JH NFL 18 4C 39 NC en
28. is as much as possible in that it collects all the key measurements required with the idea that in principle these can be used to make decisions about plant growth 94 I never had time to implement at least one of those decimal point driving tricks For me who has a working knowledge of the system it 1s easy to imply the location of the decimal point but for others the display may be somewhat cryptic All in all this submission in my opinion represents a good effort of what can be achieved in a relatively short period of time A lot of work is still required before the SmartPlanter can make its claims When I reach this point will I still use the NEC microcontroller It makes sense because I found it mostly lacking in no way for this particular application I most likely will switch to a microcontroller with a graphics LCD display I had no 1ssue with the tools provided and generally things worked the first time around for whatever it is that I set out to make the chip do I have definitely enjoyed and gained from this experience Q0 Final shipped SmartPlanter demo program 90
29. level in the SmartPlanter is reaching low levels This is meant to prompt users to refill it Depending on the plant species this water reservoir should last about 3 to 4 weeks That is enough to safely go on a vacation without worrying about losing plants due to under watering for indoor plants For outdoor plants the SmartPlanter is designed to collect rain water in its reservoir This further extends the period of time that the plant can be unattended and the reservoir topped off VCAP Buzzer P23 CMPTOUTO TO I used the P23 CMPTOUTO TOZ2 signal to drive the buzzer because T02 can generate square waves with no software overhead Hence it does not require bit banging a port to generate an audible square wave Without this feature I would probably have used a timer or implemented an oscillator around the buzzer circuit Here 1s the software that drives the buzzer code removed for publication 92 To use the buzzer use the following code code removed for publication To have the ability to change the buzzer tone frequency on the fly without having to turn it on again simply change the SetBuzzerFrequency macro to code removed for publication In other words just change the CR value on the fly without turning T02 off A note in the upd78F9418 recommends turning TO2 off before setting CR because it may fire spurious T02 interrupts but in this application we don t care about this because the T02 s interrupt mask is always
30. ll make use of the following functions found in serial h and serial c The serial interface on the M Station and the associate MSTTERM software 1s useful however since MSTTERM does not seem to want to remember the baud rate last setting I found it annoying having to set it up every time I used the KORE9418 at a baud rate other than the default of 9600 I preferred higher rates but ended up using mostly 9600 because of this annoying thing about MSTTERM This is reflected in the serial software 27 Serial h code removed for publication Serial c Liquid Crystal D isplay D river This application definitely calls for a nice graphic LCD display perhaps even a custom designed LCD with 1cons to help users select plant species and other configuration parameters Unfortunately by the time I heard about the Mad Design Contest and created an application all of the graphic LCD based development boards had already been spoken for So I used the 7 segment LCD of the upd78F9418 and made do with it Finding low cost 7 segment LCD modules in unit quantities 1s not an easy task I eventually honed in on two offerings One was a 4 digit LCD available from DigiKey and the other a 4 digit 7 segment LCD found at an online electronic surplus store at a mere 4 each Four digits are the best I could find in small quantities and I planned to use the most digits possible The upd78F9418 1s capable of driving a maximum of 3 digits and associated decimal po
31. ly on the availability of solar power A combination of battery and solar power is therefore a reasonable solution I did not want to have to use a solar panel that is too large because it would interfere with the ergonomics of the planter Whichever solar panel 1s to be used has to be small discrete and fit nicely within the planter I found high efficiency solar panels that are a mere 36 x 36 mm capable of delivering high short circuit currents and an open circuit voltage of 5 V or more in direct sunlight These are perfect for trickle charging 3 6 V Lithium Ion batteries My solution is based on the use of this type of solar panel charging common 3 6 V Lithium Ion batteries This way the batteries will last a while before having to be replaced For the solar panels I used two Panasonic BP 24 2221 solar panels in parallel The solar cells are 37 x 33 mm in size They provide 5 5 volts open circuit at 15mA short circuit 37 in noon sunlight These are the SC3733 37 x 33mm Panasonic Sunceram Solar Cell from SolarRobotics LTD For the battery I used a single 3 6 V 1050 mAH Lithium Ion rechargeable battery made by A amp TB Japan These were purchased on sale for 1 each Two of these solar panels in parallel should deliver at least 20 mA in moderate sunlight which is still not enough to drive a water pump motor Even those tiny motors found in ZipZap remote control cars draw around 40 mA I did not want to drive the pump motor from t
32. off Keypad Block D iagram UU P46 Key return mode register 00 KRMOO n P40 KRO C l P41 KR1 e P42 KR2 Q P43 KR3 o n Falling edge detector KRIFOO set signal P44 KR4 e o P45 KR5 O m Standby release KRMK e signal What is Missing I had been working on this SmartPlanter idea as a viable product long before the Mad Design Contest came along The NEC s Mad Design Contest provided the wonderful opportunity of not only having my ideas made public but giving me access to the design tools the software and the hardware The NEC s upd78 series of microcontrollers seemed like a good fit for this application therefore I decided to participate I knew all along that this project would require considerable research and that I may not finish it in time 99 One of the things that 1s not visible or aspects of this project that I am not stressing has to do with the mechanical design aspects I researched the market extensively for a low cost pump that works on 3 V or less and there simply isn t any If there 1s one out there that I missed chances are it works on 12 V or more and is some kind of high end medical device and costs a fortune This led me to designing a low power pump from scratch For this purpose I purchased a lathe and a milling machine and experimented with various ideas The pump that 1s included in this submission represents the first working prototype of such a pump I am delighted with its
33. on for it is battery operated and is free of mains hum besides I did not expect the input to be noisy Experience has shown that solar cells have a lot of high frequency variations The idea was to implement a somewhat generic A D converter signal conditioning add in board for the KORE9418 that could be used in other applications Although the printed circuit board implementation caters for the circuit above components can be omitted to simplify things whenever needed but at the very least for this application the potential divider section is required The microcontroller operates under a stable 3 0 V provided by a LDO regulator as seen in the power section of this document The chosen 2 5 V reference is the REF3125 a Burr Brown product from Texas Instruments It was chosen for its low quiescent current of 100 uA its low dropout of 5 mV and its 20 ppm C drift performance In addition an output capacitor 1s not required In this low noise application the recommended input capacitor was omitted without any effect on performance REF3125 DO aie PIG 1 Pash 46 Here is the complete circuit diagram for the analog input plug in board pE ERAN E EL IAN A IN ALE EZIAINZ EIA col nicTHP IH D rs TTA TP Alc PT zEIIN TP zIT n zEIIWTP ITH 24lIN TP nIT In zxlrhiPTn TnI TD zazle lii xn zilcnITxn znlsr I N I E E El En Pa 2 REF REF REF EOI OIE IND 1554 PEA a PELA ME E ss RIA I LES AMREF AMREF
34. plement a subset of this software technique for the upd78F9418 The message queue paradigm simplifies and clarifies software in the way that it decouples the originator of an event to the code processing the event Too often I have seen complicated interrupt handlers that do too much and communicate state information with the main loop through flags Surely there 1s a more elegant approach Just because it is at the bare silicon level does not mean that it has to be quick and dirty Embedded software can be elegant and simple to maintain too The idea is based on a queue or FIFO data structure Messages are entered in the queue at one end and removed at the other end Code that inserts messages in the queue should never remove them from the queue for simplicity Typically code that en queue messages are interrupt handlers and code that de queues messages are in the main program s processing loop Message Queue db Message O OOO 2 Hardware Interrupt Message pump Interrupt handler Messages originate from events These are generally true real world hardware events such as a limit switch interrupt but they can be software events too such as to convey a change of state in the scope of a program Messages can carry parameter values as well 24 In the Windows world a message has a type generally an enumeration or define with a name such as WM CLOSE Bbut it 1s also capable of car
35. psum blocks actually do not measure soil moisture directly instead they measure soil tension which is related to the amount of water that a plant soil combination can absorb water This measurement is often referred to as soil suction or pressure the ability of the soil to draw water The units are thus expressed in Kilo Pascal What makes this technique of soil measurement attractive 1s the relatively low cost of the sensor and the simplicity of the associated measuring circuit In addition moisture measurement is independent of soil type G ypsum block soil moisture sensor construction Gypsum blocks are cylindrical in construction with a diameter of 25 mm and a length of 35 mm Two concentric rings of wire mesh are embedded in the gypsum block and make up the electrodes thus confining the flow of electric current between the electrodes to the interior of the block eliminating the effects of soil conductivity Conductivity 1s not a true measure of moisture as it varies with PH and its effects are not desired The gypsum acts as a buffer against the effect that salts present in the soil might have on the electrical conductivity A controlled mixture of gypsum or Calcium Carbonate CaSOs also known as Plaster of Paris 1s placed between the electrodes The resistance between the electrodes varies with the moisture content of the gypsum block which in turn varies with the suction pressure in the surrounding soil Measuring the AC resistance of th
36. ry 10 seconds code removed for publication NO Here 1s the real time clock module This 1s the header file watch h code removed for publication This 1s watch c code removed for publication This is the piece that deals with the watch timer and inserts a MSG SAMPLE type message in the queue at the sample rate Here 1s the short and sweet header file rtcq h code removed for publication And here is the implementation file rtcq c code removed for publication The important bit is the watch timer interrupt handler WATCH ISR It simply counts the number of 2 second ticks since this is the way the watch timer works This handler is called every Y second To count in seconds we simply count the number of half seconds If g sruiHalfSeconds 2 0 is true on every second This gives us an if statement where the body executes every second On every second we update the real time clock and calendar data structures via a call to update watch We then check 1f we have reached the specified sample rate in seconds and generate a message to the queue This makes the call to GetMessage in main succeed with the message type MSG SAMPLE Like I said earlier other types of events can be generated in a similar fashion by inserting messages of different types in the queue This technique is also useful for handling interrupt driven serial communications A serial receive interrupt handler routine would buffer chara
37. rying two parameters a 16 bit integer as WPARAM or a 32 bit integer LPARAM LPARAMS can represent pointers hence a message can in principle carry with it a pointer to a huge data structure In this reduced implementation a message only has a type and a single parameter Message Type Parameter The definition for a message message type and parameter are as follows Here are the full contents of the MessageQueue h header file code removed for publication To work with a message queue is as simple as working with a FIFO data structure with just one complication Code that en queues and de queues messages should never step over each other to make the state of the queue inconsistent Therefore we need a way to synchronize access to the queue variables This can be done with a semaphore or flag that should be used by only one piece of code at any time Here is the code code removed for publication This 1s all there is to it Now observe how this device simplifies and makes things clean In this usage sample I want to repeatedly take sample readings every 10 seconds or every hour the duration does not matter Here is a typical usage of the message queue and I use it in most of my time based applications but it can also be used to queue in keypad entries in the queue by a keypad interrupt handler for processing by some main processing loop Here is the queue in action This sample sends the time and date to the serial port eve
38. ssing board which is the next topic of discussion T he Analog to Digital converter The 10 bit A D converter feature of the upd78F9418 is essential to this application It is used to perform power management and actuators control The upd78F9418 user manual recommends the following protection circuitry on the analog inputs which I have implemented If noise greater than AVrer or less than AWas is likely to come to the AVner pin clamp the voltage at tha pin by attaching a diode with a small Vr 0 3 V or lower Reference voltage input AV REF C 100 to 1000 pF l All my measurements are ratio metric and make use of a potential divider The voltages to be measured include the solar cell voltage and supercapacitor voltage The solar cell voltage may rise as high as 5V under direct sunlight conditions and this voltage source charges the supercapacitors which are rated at 5 5 V The recommended value of A VREF is 2 5V which is about half of the voltages that I am trying to measure I used a simple potential divider to halve the voltages fed to the A D inputs I compensate for it in software using a multiplying factor of 2 The A D input circuit 1s as shown below 45 _AVREF 2 5 Voltage to be measured Potential divider filter capacitor Overvoltage protection J 2l oo EH g dL i oe Mi a BINO AINB E 4 dE 100 pF oes AGND A ND ACND AGND This input circuitry is probably overkill for this applicati
39. t the output frequency varies between 28 Hz when the block 1s dry to a maximum of around 1 3 KHz when wet immersed in water The circuit can be considered as a resistance to frequency converter A typical gypsum block resistance curve as a function of soil tension is as shown below c ue D BLOCK RESISTANCE IN OHMS Note the S shape of the curve s relationship This implies that at the extremes that is extreme dryness or wetness it the variations in resistance are the smallest Although the block s resistance can be measured using strictly analog techniques using an AC bridge followed by a precision rectifier and filter feeding to an A D converter the resistance to frequency approach offers better resolution and has a dynamic range of slightly more than 1000 Measuring soil tension is hence a matter of accurately measuring the frequency or period of the output pulse train of the circuit above Period measurement technique The NEC uPD78F9418 s 16 bit timer with capture register driven by an external edge detector as trigger is ideally suited for this type of measurement VDD VDD P ES Resistance as S To Gupsum Frequency M y INTPS TCAPS Block Converter VSS KORE9418 16 bit timer moda control register 52 TMICSO pardo tH LL L TOS P25 16 bit compare register 50 CARI INTP2 16 bit timer mode control register 50 IMTTMS
40. ve V activated by motor M2 Fertilizer flows from E3 through pipe P6 and valve V to the mixing point reached via pipe P7 Watering The water intake for the pump is the V1 V2 container via P1 and the outlet is through pipe P3 leading to interchangeable sprinkler head SP SP can be sprinkler or mister heads selected for maximum plant coverage El signals Sl and S2 carry fertilizer and pump motor control signals from the controller enclosure E2 running through sealed pipe P4 to enclosure El 20 E2 Enclosure E2 contains a micro controller MC a Lilon battery B and an audible buzzer BZ A user interface 1s provided through a liquid crystal display panel LCD and a keypad SW solar power The unit 1s solar powered via solar panel SP 21 Controller block Diagram Moisture Sensor Block Diagram 22 Power Sensing and Actuator Block D iagram 23 T he message pump paradigm Perhaps I have been programming under the Windows operating system for too long and have fallen in love with the concept of message pumps But I find that it has a tendency to simplify the software in both real time systems and in embedded systems Therefore I decided to im

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