1. RAINWATER HARVESTING CONTROL SYSTEM
Deval Dixit - M.Eng Electronics 2013
INTRODUCTION
c
TECHNOLOGY BACKGROUND
The rapid expansion of urban areas in Ireland , along with increased demand from both the
industrial and domestic sectors, is posing significant challenges for municipal water supply
resources and infrastructures. The water demands in such a large volume is fulfilled by
neighbouring catchments. Out of which 1% of water is utilized for potable quality .
So as to reduce the dependency on potable domestic supply, the potential substitute is
rainwater harvesting. Harvested rainwater is renewable source of clean water and is ideal for
domestic utilization.
PROJECT BACKGROUND
Given Irish rainfall levels,
rainwater collected for non-
potable uses has the potential to
replace a considerable portion of
water consumption.
REFERENCES
[1] Capacitive Touch Software library, SLAA490A– Texas Instruments
[2] Mixed Signal Microcontroller, MSP430G2452,SLAS-722F, www.ti.com
Texas Instruments
[3] Fewkes, 2006, The technology, design and utility of rainwater
catchment systems, London.
Capacitive sense technology is employed as liquid level sensor. It is used to overcome the
traditional issues associated with mechanical levels or push button switches for measuring the
water levels inside the tank. This liquid level sensing uses point level measurement.
Point level measurement: In this type of measurement, sensors are placed at discrete levels on
the tank determining the level of water in tank as tank full detection, tank empty detection.
The MSP430 LaunchPad supports MSP430G2xx Value Line MCUs. These devices operate up
to 16MHz, feature up to 16kB Flash & 512B RAM. They also offer integrated ADCs, timers,
serial communication modules etc.
MSP430G2452 Capsense board is ultra low power mixed signal microcontroller with built in
16 bit timers, and up to 16 I/O touch sense enabled pins with built in communication using
the USI and have high performance analog comparator. In the project it typically applications
captures the analog signals, covert them to digital values and then process the data for
transmission to a host system.
Supervisor – Dr. Ken Deevy
Water Consumption In Houses In Ireland.
Capsense Board encapsulate on
MSP430 LaunchPad .
Principal of point level detection of
water in an opaque tank
Capacitance Calibration RO Method: With increase in capacitance (C1 to C2). The number of
oscillator cycles counted within the gate time decreases. When capacitance decreases (C2 to
C1), the number of cycles within the gate time increases. Capacitance and counts have an
inverse relationship in the RO method.
 Time Base 1 connected to RO circuit.
 Time Base 2 connected to system clock such as DCO.
OBJECTIVES
 Col_S1 (Sensor): Sensor will be high when water is above this level. Tank is Full.
 Col_S2 (Sensor): This sensor will be high when water is below this level. Tank is
Empty.
 Attic_S3 (Sensor):This sensor will be high when water is above this level. Tank
is Full.
 Attic_S4 (Sensor):This sensor will be high when water is below this level. Tank
is Empty.
 Rain sensor_S5: The sensor determines the rain action and will be high when
rainfall occurs.
 (All 5 sensors are capacitive type water level sensors )
 Automated Flap: This flap is controlled automatically through algorithm
written in control system. Remove first flush water from down pipes after the
rain action ends.
RWH control system Architecture
Relaxation Oscillator Measurement
Signal List For The RWH Control System
 Write algorithm for MSP430G2452 chip to evaluate the capacitor value
that determines the Water level sensing actions.
 Write software for MSP430G2452 chip UART half- duplex mode (only
transmit) to PC. Through FT230X USB-UART FTDI cable.
 Show sensor response in the Multi Chart Diagnosis tool. This tool will
receive calibrated data (capacitance value)from chip and plot the
response.
 Write control algorithm module that will monitor the sensors and water
supply either from Mains valve or RWH Tank pump.
 Integrate the whole algorithm modules to implement RWH control system
assembling.
Multichart
Diagnostic tool
 Harvested rainwater has potential to provide augmented source to treated
mains water for non-potable uses.
 Capacitive sensing can make devices more reliable and their
implementations in RWH system will value to customers as well as reduce
maintenance expenses.
 Low cost sensor application leads to cost effective control system .
CONCLUSION
Variation in Capacitance as
Dielectric between the
electrodes changes in the
tank.
28/5/2013