Neonate Growth Monitor
Target Product Profile (TPP)
UNICEF Height + Length + Weight Measurement Device
Design Aim from TPP
Bio-transducer for TPP
Strain gauge and rotary encoder
Design Inputs
Ease of Use
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< 3 steps to use with minimal training and calibration
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Small and portable
Suitability for Target Environment
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Able to withstand harsh climates and storage conditions
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5 year operational life in -10 to 45 ℃ and 80% humidity
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Rechargeable battery lasting > 48 hours with automatic shut off and low power notifications
Range and Accuracy
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Display in cm and kg with one decimal digit
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Accuracy and precision of ± 3 cm for length and ± 0.3 kg for weight
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Range of 5-100 cm
Early Iterations
The first enclosure design. The strain gauge at this point was too sensitive, as it was changing from the swinging of the key ring.
Testing the tare button and rotary encoder on the prototype after adjusting strain gauge sensitivity, but more adjustments were still needed.
Design Solution
Arduino and transducers
inside casing
Rotary encoder for length and height measurements
Carabiner attaches to baby wrap/blanket
Strain gauge
LCD display
The final solution being demoed.
Required Components
Transducers
Strain Gauge
● Is attached to a load cell and measures the deformations
● These measured deformations are converted into electrical signals
Load Cell Amplifier
● Used to amplify the changes in electrical resistance measured by the strain gauge.
● Output is a analog signal representing weight.
Digital Filtering
Digital filtering approach:
● Moving average filter instead of a low-pass active filter
○ Will get rid of high frequency noise caused by movements from the infant and user
○ Smooths out short-term fluctuations in the signal to simulate a low-pass filter
○ Implement a window size (number of samples to average) to get a balance between strain gauge responsiveness and smoothness
Signal Analysis
Once the digital signal is filtered, the series of values must be turned into weight values by establishing a relationship between digital values and weight- this is done through calibration.
Steps:
● Measure known weights with the device to create a reference and
establish a connection between digital signal and actual weight.
● This process will give a calibration factor that will be applied within the Arduino code to automatically convert digital signal values to weight values.
● The weight in kg will then be displayed on the LCD screen.
Signal Display
Arduino UNO to collect data and transmit to an LCD display which hosts signal processing code internally
● LCDs are cheap and don’t consume much power
● Display measurements in kilograms (kg) and centimeters (cm)
Test Plan Overview
The following components were tested and all tests passed.
Awarded Best Overall Prototype
Special thanks to Bradley Hilger and Anna Ryder for their teamwork on this project, and to Dr. Robert Stone for being a wonderful instructor and mentor during the project.