Transcript Our Poster - College of Engineering | UMass Amherst

Maji Safi
Jason Arble, Peter Balkam, Kaitlin Menzie, Minh Tran
Faculty Advisor: Prof. Paul Siqueira
Abstract
System Overview
Maji Safi is a remotely controlled device allowing users
with a SMS-enabled cell phone to access measurements
of physical water parameters where the device is
deployed. Users text the device to issue commands to
detect the presence of water, return turbidity, temperature,
and pH measurements. The device then texts a web server
(running Twilio’s web API) to report measurements. The
server interprets the measurements and reports back to
users via SMS. Our device targets countries experiencing
economic water scarcity, where lack of information
regarding the water quality of unimproved water
resources leads to a poor water-delivery infrastructure.
Admins
● Water Detector (yellow)
● Temperature Sensor
(violet)
● Turbidity Sensor
(green)
● pH Sensor (red)
Data can be used to
supplement chemical
testing, allowing officials
to monitor sanitation and
correlate water conditions
over time with growth of
bacteria.
People
Scientists
Device
Control
Request
Block Diagram
Application
Control Signals
Sensor Readings
Sensor Readings
Sensing
The diagram (above left) are example use cases. We intend
to have it be used as a scientific instrument, tool in the
design and regulation of water distribution infrastructure,
and a means by which locals learn about the water around
them.
Above right illustrates possible deployment sites: refined
wells, unprotected wells, and small bodies of exposed
surface water.
Device Specifications
Parameters
Goal
Actual/Dev.
Device Volume
4400 ㎠
4000 ㎠
Housing
Water-Resistant, Buoyant
Water-Resistant, Buoyant
Server-User Response Time
< 5 minutes
< 1 minute
Phone-User Response Time
< 1 minute
< 30 seconds
Turbidity Sensor Accuracy
± 0.01-5 NTUs.
± 100 NTU
pH Sensor Accuracy
± 0.5
±1
Temperature Sensor Accuracy
± 3°C
± 3°C
Power Consumption
≅ 1.4 W
1.35 W
Battery Life
12 hours
18.5 hours
Deployment Duration
1-3 Months
1-3 months
SMS Text($)/Day
$0.01-$0.03 (1 SMS/Day)
$1.00-$5.00 (1 SMS/Day)
Cost/Device
<$100
$227.92
● Solar panel extends the deployment time, allowing
continuous measurements to be taken for weeks or
months.
● Sensors are fairly accurate, power efficient, but
could be improved upon or specialized for different
applications
Water Detector
The water detector uses
simple voltage divider (shown
right) whose output voltage is
read by the microcontroller. If
this voltage is between a
threshold between one and two
volts and makes a binary
decision on whether or not
there is water.
This threshold was
determined from an experiment
involving measuring the
resistance of different states of
water and calculating the
output voltage. This data is
shown in the table to the right.
Substance
Impedance
(1 cm)
Output
Voltage
Tap water
86 kΩ
1.50 V
Sugar Water
99 kΩ
1.65 V
Oatmeal Water
75 kΩ
1.36 V
Garlic Salt Water
65 kΩ
1.23 V
Rice Water
90 kΩ
1.55 V
Mud
4 MΩ
4.76 V
Acknowledgement
Special thanks to our advisor Professor Paul Siqueira,
our evaluators Sandip Kundu and Hossein Pishro-Nik,
Kris Hollot, Francis Caron and Professor John
E.Tobiason.
Department of Electrical and Computer Engineering
ECE 415/ECE 416 – SENIOR DESIGN PROJECT 2016
College of Engineering - University of Massachusetts Amherst
SDP16
User Interface: Web App
Sensor Calibration
Using the manufacturer’s
specifications(shown right) for
the turbidity meter, we found a
linear approximation of the
voltage-NTU relationship. The
pH and temperature sensor are
calibrated in a similar manner.
Water Detection Sensor Accuracy Improvement
User Interface: Android Application
Sends formatted texts to the device or web app
● No robust solution with additional hardware
Reads in SMS based responses from device
● Software solution:
○ Use the pH sensor to make the logic more
robust
○ If the pH is between 5.6 (acidic rain) and
8.5, it likely that there is water
Sampling Code Functionality
● The microcontroller will take samples at a set interval.
● After a set time the samples are averaged and the result is sent
out.
● Both the sample time and the sample rate can be changed
remotely by SMS.
Server
Twili
o
Bubble
Twili
o
Data Users
App (node.js)
Website
Power Supply
Given that our device must
operate remotely for long periods
of time, a solar panel was the only
option. This along with a Li-ion
battery ensures our device can
remain powered indefinitely.
User (water
gatherer)
Subsystem
RDB (PostgreSQL)
Power
Consumption
Server (AWS EC2 instance)
Microcontroller
0.6 W
GSM Module
0.6 W
Sensors
0.15 W
Total
1.35 W
Mobile
Site
Device Admins
● Node.js application built on express.js and running on an
AWS EC2 instance.
● App communicates with Twilio for SMS functionality
You can communicate with
Maji Safi!
● To see all the devices in an area, go to majisafj.me
● To use your phone like a device, make an account on
majisafi.me and register your phone as a device
● To query the server as a water collector, text a valid
location to:
Enclosure Design
Alpha
Beta
Alpha: Plastic is difficult to
seal
Beta: Foam affixed to achieve
buoyancy & stability
Parameter Alpha
Device
Beta
Device
Waterproof
No
Yes
Buoyant
Yes
Yes
Stable
Yes
Yes
Contains Entire
System
Yes
Yes
Cost Effective
No ($62)
Yes ($30)
Compact
Yes (4000 ㎠)
No (5600 ㎠)
Aesthetically
Appealing
Yes
No
Printed Circuit Board (PCB)
The GSM module, sensors, power supply and microcontroller
all come together at the PCB. The schematic for the PCB is
shown below on the left while the physical layout is shown on
the right.
(781) 325-4725
Cost
Item
Development
Cost
Production Cost
(1000)
Water Detector
$0.10
$0.00729
TSW-10 Turbidity Sensor
4.66
3.95
pH Sensor
29.50
27.19
Temperature Sensor
1.50
1.35
SIM Card
0.99
0.99
GSM2-Click w/ antenna
49.00
49.00
ATmega328P-PU
3.10
1.85
NXP LCP1768
46.00
Abandoned
8GB Micro SD Card
7.63
6.14
SD Card Slot
1.66
1.66
Resistors/Capacitors/16MHz Clk
1.02
0.29115
Li ion battery x2
29.90
23.92
Solar Panel
29.00
23.20
DC-DC Converter
9.95
9.95
Charger
17.50
17.50
3D Print
60.92
60.92
Total
292.43
227.91844