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8/13/2019 Design of Irrigation Control Unit Using PSoC
Drip or trickle irrigation refers to the frequent application ofsmall quantities of water at low flow rates and pressures.
Rather than irrigating the entire field surface, as withsprinklers, drip irrigation [2] is capable of delivering water
precisely at the plant where nearly all of the water can be used
for plant growth. Because very little water spreads to the soil between the crop rows, little water is wasted in supporting
surface evaporation or weed growth. The uniformity of
application is not affected by wind because the water is
applied at or below the ground surface. A well designed andmaintained drip irrigation system is capable of an applicationefficiency of 90 percent. The trickle irrigation system with the
proposed control unit offers the following advantages
1. Reduced Weed germination: Water is directed to the
crop, leaving the area between the rows dry, so weedseeds located there are less likely to germinate
The proposed design utilizes [4] Programmable System OnChip platform by Cypress Semiconductor. One PSoC mixed-
signal array integrates a Microcontroller with as many as 100
peripheral functions. It provides low cost design through
reduced chip counts streamlined manufacturability, and
improved power efficiency.
The PSoC comprises a built-in MCU with flash memory and
SRAM link to essential system resources
•Sleep and watchdog timers•Multiple clock sources that include a PLL
•Internal main and low-speed oscillator
• External crystal oscillator for precision, programmable
clocking
PSoC devices can have upto two multiply & accumulators
(MACs), which provide fast 8-bit multipliers or fast 8-bit
multipliers with 32-bit accumulate, up to two decimators for
digital signal processing applications, I2C functionality for
implementing either I2
C slave or master, and availability of afull-speed USB interface
FIGURE 2 PSoC TOP LEVEL ARCHITECTURE
PSoC mixed-signal arrays free designers to route any signal to
any pin, shedding the constraints of a fixed peripheral
controller. In addition, global buses allow for
signal multiplexing and for performing logic operations,
eliminating the need for a complicated digital-logic gate
design.
IV. PSOC BASED DESIGN
The distributed sensor system [example WSN] collects details
of parameters like moisture content and temperature fromdifferent sectors of the field. The signal send by the sensor is
boosted up to the required level by corresponding amplifier
stages. This is further fed to A/D converter modules inside the
PSoC of desired resolution to obtain digital form of sensed
input for microcontroller core, which can be used in the
system to monitor sensed values and the current status ofrespective valves with the help of a LCD module. The
solenoid valves are controlled by microcontroller core
through relay drivers. A Chemical injection unit is used to mix
required amount of fertilizers, pesticides, and nutrients with
water, whenever required. This is again controlled by the MCcore based on a Look Up Table, programmed in. The LUT isalso programmed with PWM output rating corresponding to
the sensed value of temperature and pressure. As per the duty
cycle of the PWM output the speed pump motor can be varied
which further controls pressure of water. A flow meter is
attached for analysis of total water consumed. The requiredreadings can be transferred to the Centralized Computer for
further analytical studies, through the serial port present in the
PSoC. The in-built timer in PSoC can be configured, to
operate parallel with sensor system. In case of sensor failure
the timer turns off the valves after a threshold level of time,
which may prevent further disaster. The control unit may thenwarn about the pump failure or insufficient amount of water
input with the help of flow meter which is fed back to the MCcore for adjusting motor speed to control the injection rate
accordingly. The MC core controls the relay driver to control
the valves which are connected to the drip lines fitted with
emitters. The lateral drip tapes are polyethylene tapes with built in emitters. They are available in a variety of diameters,
wall thicknesses, emitter spacings and flow rates.
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