Course:
Embedded Systems and Software 55:032
Instructor: Dr. Anton Kruger
Abhijeet Kher
Aakant Taurani
Why is measuring water turbidity important?
 Particles can be suspended in water
 Test for water quality
 Clear water is not always clean water
 Drinking dirty water can cause many GI
and other health problems
 Especially a problem in developing
nations
Cost
Our Project
Source: http://www.nextag.com/turbidity-meter/shop-html
~$60!!!
Components of Our Turbidity Meter
Phototransistors
Vial
Slot
LED
LCD
Microcontroller
Circuit Schematic
470 Ohms
Transistor 1
LCD
100k
Transistor
2
Voltage
Ratio Vs NTU Rating
100k
Voltage Ratio & NTU Correlation
 Voltage Ratio =
Voltage at Transistor 1
Voltage at Transistor2
 Using the polynomial equation in the
graph, we can obtain the
corresponding NTU rating
 Higher the Voltage ratio, lower the NTU
MS Excel plot of Voltage Ratio Vs. NTU Rating
 Significant error +/- 5 NTU
How it works:
Vial Inserted
LED Emits Light
Through Sample
or Gets Refracted
Phototransistors
Pick Up Photons
Output Voltage
Ratio and NTU
Rating to LCD
Screen
Calculate Voltage
Ratio and
Respective NTU
Rating
Signal Converted
to Voltage
Possible Improvements
 Building a more compact container
 Fixing/mounting LED and Transistors firmly to
prevent shock damage
 Error correction to provide a more accurate reading of
voltage ratio
 Using a custom made circuit to cut down costs further
 Increase accuracy by using more test samples
Demo
Questions?