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Group 16 Emily Jaeger Amy Rosenthal Nicole Typaldos. A New Minimally-Invasive Bedridden Patient Weighing System. Current weighing techniques are inadequate and often dangerous Lifts require suspension of patient over the bed - PowerPoint PPT Presentation
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A NEW MINIMALLY-INVASIVE BEDRIDDEN PATIENT WEIGHING SYSTEM
Group 16Emily JaegerAmy RosenthalNicole Typaldos
THE PROBLEM Current weighing techniques are
inadequate and often dangerous Lifts require suspension of patient over the
bed Uncomfortable for patient and time consuming
and difficult for nurses Built-in scales have low accuracy (1% of
patient weight) Beds with built in scales are expensive,
causing a low adoption rate
DESIGN REQUIREMENTS Weigh bedridden patients within 0.23 kg (0.5 lb)
and with minimal movement of patient. A single user with no additional training to operate
the device and obtain patient weight in less than 5 minutes.
Device will not interfere with normal patient care. Adult and obese patient weighing 22.7 kg to 453.6
kg (50 lb to 1000 lb) should remain comfortable. Automatic readout to display screen. The device will cost a maximum of $10,000.
A COMPARTMENTALIZED FLUID FILLED BLADDER The Bladder
Location of the weight sensing The Controller
Allows the user to interact with the device and stores all important data
The Cart Contains a pump and reservoir to fill, drain,
and store the fluid when not in use
ANALYSIS – THE BLADDER Smallest bed deck size: 90.2 cm x 203.2
cm Bladder dimensions selected to be 90 cm
x 200 cm to accommodate all bed sizes The bladder had to be thick enough to fit
the sensor while also minimizing the volume of water The internal thickness is 3 cm in order to
accommodate the sensor
ANALYSIS – THE BLADDER Maximum weight to be held is 453.6 kg
(1000 lb) Given the area, this translates to a
maximum internal pressure of 8.0 kPa
ANALYSIS – THE CONTROLLER Power Requirements for Each
Component
Component Input Current Input Voltage Range Power Range
LCD Display 2mA 5V 10mW
MCU 10mA 5V-6V 500mW-600mWPressure Sensors (4) 8mA 7V-8V 56mW-64mW x (4)
16- Key Keypad 1.8mA 4.5V-5.5V 8.1mW-9.9mW
Fluid level sensor 10mA 5V 50mW
TOTAL 792.1mW-925.9mW
ANALYSIS – THE CART Pump Selection
Needed to be able to overcome the maximum pressure within the bladder to refill if patient is present
Needed to fill within our set goal of 5 minutes
To pump up to 53 L (14 gallons) in 5 minutes, or 2.8 gallons per minute minimum
DETAILS – THE BLADDER Material: PVC Tarpaulin (5 mm thick) Dividers: High Density Polyurethane
(HDPE) (2 mm thick) Overall dimensions: 90 cm x 200 cm x 3
cm 4 compartments each with a pressure
sensor
DETAILS – THE BLADDER Pressure to Weight
Each compartment contains a pressure sensor
The tare value of each sensor is stored in the controller
Using the area of the specific compartment, the weight on that compartment is obtained
These pressures are then summed by the controller to output the patient’s weight
DETAILS – THE CONTROLLER Internal Components
LCD Display High contrast Displays desired 40 characters Minimizes glare in the hospital
setting MCU
Takes at least 10 inputs Can store information and still
obtain new information 16-key keypad
Numbers: 0 through 9 Function keys: Tare, Get weight,
Adjust, Units, Cancel, Yes
DETAILS – THE CONTROLLER External Components
4 Pressure Sensors (140PC Series, Honeywell)
Gauge input Linear within desired range
Fluid Level Sensor (eTape, Milone Technologies)
Varies resistance based on fluid level
DETAILS – THE CART Cart Frame
Constructed from alloy 6061 aluminum 2.5” and 2.0” extruded square tubing (1/4”
thick) 3/64” thick sheets for platforms 1.25” extruded circular tubing (1/16” thick)
Tiered design to minimize dimensions
DETAILS – THE CART Water Reservoir
Material: HDPE (1/16” thick) Volume
Maximum: 66.8 L To fill line: 57.4 L
Opening near base with fitting for connection to pump
Design allows for higher fill accuracy as volume lowers
DETAILS – THE CART The Pump
Rotary vane pump (McMaster-Carr) 19.7 L per minute (5.2 gallons per minute) Maximum pressure of 1.66 Mpa (241 psi)
DETAILS – SAFETY CONCERNS Cords and tubing pose a tripping risk High pressure produced by the pump,
requires safety labeling and careful usage Water spill risk due to the tubing Controller displays warnings and
confirmation screens when certain functions are called
Training required for nurses to ensure proper usage
PRODUCTION – THE BLADDER
ComponentQuantity Unit Price Total Cost Lead Time Supplier
PVC Tarpaulin (per square meter) 2 $15.00 $30.00
30 to 45 days
CTA Hi-Tech Textiles Co.
In order to seal the bladder, high frequency welding is used.
Production cost ~$100
PRODUCTION – THE CONTROLLERComponent Quantity Unit Price Total Cost Lead Time SupplierKeypad 16 key customize 1 $28.68 $28.68 1 week Digi Key
LED display 1 $24.68 $24.68 1 week Allied ElectronicsControl Panel Enclosure 1 $58.98 $58.98 1 week OKW Enclosures, IncPressure Sensor 4 $127.75 $511.00 1 week Jameco Inc.Keypad Encoder Chip 1 $5.19 $5.19 1 week Jameco Inc.3-PIN Sensor connector 4 $0.40 $1.60 1 week Allied ElectronicsPCB circuit wiring black (100 ft roll) 1 $7.95 $7.95 1 week Jameco Inc.PCB circuit wiring red (100 ft roll) 1 $7.95 $7.95 1 week Jameco Inc.PCB circuit wiring white (100 ft roll) 1 $7.95 $7.95 1 week Jameco Inc.6-PIN Wiring connector 1NA $8.90 1 week Allied Electronics6-PIN Wiring connector recept 1NA $8.90 1 week Allied ElectronicsAC-DC power supply 1 $11.86 $11.86 1 week Digi KeyMicrocontroller Unit 1 $7.70 $7.70 7 weeks Digi KeyPrinted Circuit Board 1 $30.58 $30.58 2 weeks Sunstone CircuitsAMP Panel mount connectors/mate 5 $1.08 $5.40 1 week Allied ElectronicsCard edge connector (connect keypad output to pcb) 1 $1.30 $1.30
1 weekAllied Electronics
Total $728.62
PRODUCTION – THE CONTROLLER OKW provides free prototype creation with
the purchase of controller housing products. The PCB printing and customization would
cost $30.58. (Sunstone Circuits) Circuit assembly and soldering could be
done by team members For mass production
Circuitry assembly would cost $158 Milling of the enclosure would cost $14
PRODUCTION – THE CARTComponent Quantity Unit Price Total Cost Lead Time Supplier
HDPE (48" x 48") 1 $20.23 $20.23 < 1 week US Plastics Corp
Female Tank Fitting 2 $12.46 $24.92 1 week McMaster-Carr
Black Hose (per ft) 12 $1.20 $14.40 1 week McMaster-CarrHose Male Fittings (set of 2) 2 $16.68 $33.36 1 week McMaster-Carr24" eTape Continuous Liquid Level Sensor 1 $49.99 $49.99 2 weeks Milone Technologies
12-24B-XD Wheel 2 $42.74 $85.48 1 week Darcor Casters
12-24-XD Wheel 2 $34.25 $68.50 1 week Darcor Casters5/16" Square Bolts, 1" length (25 ct) 1 $5.59 $5.59 1 week McMaster-Carr2.5" Square Tube Aluminum, 1/4" thick (8 ft) 1 $97.34 $97.34 1 to 2 weeks The Metal Store2.0" Square Tube Aluminum, 1/4" thick (6 ft) 1 $56.80 $56.80 1 to 2 weeks The Metal Store1 1/4" Circular Tube Aluminum, 1/16" thick (8 ft) 1 $37.30 $37.30 1 to 2 weeks The Metal Store
Rotary Vane Pump 1 $1,160.16 $1,160.16 3 days McMaster-Carr
Total $1,654.07
PRODUCTION – THE CART Aluminum components are welded
together Rate of ~$60 per hour For 2 hours of welding: $120
For prototyping, the tank is created through plastic welding of sheets of HDPE: ~$50 for fabrication Mass production would utilize injection
molding
PRODUCTION OVERALL Total cost of materials: $2,412.69 Total cost of manufacturing: $300.58
Total cost for a single prototype: $2713.27
CONCLUSIONS Attempted to solve the problem, but
many unforeseeable complications arose throughout the design process
Due to these complications, a patent was not pursued
LESSONS Communication and clear explanation
is critical when working in a team Even the smallest parts play a critical
role In preliminary design, all possible
calculations, even trivial ones, should be completed to avoid surprises later on
QUESTIONS?
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