3. The Kurber 5000
The Machine:
• A slipform paving machine
• In production for over 30 years
• Automated control to ensure proper grade
• Hall effect sensor
The Issue:
• Harsh working environment
• Uses a magnetic pendulum to determine tilt
• Moving parts are more vulnerable breaking
4. The Concept
Can we design a more robust sensor?
• Eliminates moving parts
• Works with current control system
• Easy to install and calibrate
5. Specifications
● Has an inclination range of +/-80
● Has an accuracy of +/- 0.10
● Operating voltage of 5V +/- 0.2V
● Voltage outputs are ratiometric
● Voltage output from 0v to 5v
● 00
voltage of VDD/2
● Operating temperature 0-85C
● Compensates for bumps
● 2 Prototype PCBs
● Additional bonus goals
6. Challenges Faced
● Source impedance too large for ADC
● Non-linear voltage follower output
● Eeprom writing for permanent offset storage
● Surface mounted components
● Understanding the concept of the sensor
8. Accelerometer
● Two-Axis acceleration reading
● Accelerations may be static like gravity
or dynamic as motion or vibration
● Outputs analog voltage for each axis
9. Analog Circuit Design
● DC signal only signal of use
● Design low pass filter that provides 0.5 hz cutoff frequency
● Low pass filter can as simple as RC circuit between
accelerometer output and ADC
● Voltage follower implementation
● Voltage inverter to ensure voltage follower output is linear
11. • We selected PIC24FV16KM202
• Operating voltage 2 to 5v
• 12 bit ADC
• Fine enough resolution to discern voltage changes
from the accelerometer
• 8 bit DAC
• Output can scale at least 0.1° angle changes.
• Wide range of interfaces including I²C, SPI, USB, UART
Software Design: Microcontroller
12. Microcontroller
• Capture port is configured to interrupt on a rising edge.
• Once interrupt is triggered the current value for Vx
is stored
in eeprom as Vout0g
13. Communication
● All signals that either come in or go out of the
microcontroller.
● Need to setup ADC/DAC to receive/output analog signals
● We used these equations to calculate ADC sensitivity and
DAC resolution.
14. ADC/DAC Setup
• Setup ADC to samples of the X and Y channels.
• Each sample takes 14*TAD = 62.5uS
• The ADC samples until ADC buffer is full (16 samples).
• This gives a sample frequency of 7.142kHz.
• The average of each channel is taken (8 samples each).
• This oversampling and averaging also acts as a LPF
• Variable passed to DAC Data and outputs per data sheet
• Variable = angle*16+128, which gives the desired output
voltage per angle. It is also ratiometric
17. PCB Design
● Same Dimension as control board
● Inputs: Power, Calibration offset
● Outputs:
○ Analog
○ Digital UART output via RS232
● Header for interface with control board
● On-board switch and LEDs
○ Indicates + or - with blinking indication
18. Printed Circuit Board (PCB)
● Large ground plane
below accelerometer
● Debug header
● Pass through header
● PikKit 3 interface
● On board calibration
20. Design Verification
● Verified angle mathematically with the analog output
● Verified UART with RS-232 cable and putty software
● Control board interface tested
● Constructed a miniature Kurber 5000 for testing
21. Customer Feedback
“Just finished my initial evaluation.
The device appears to function
exactly as intended, good work.”
-Rick Bergenheier
23. Conclusion
✔ 00
voltage of VDD/2
✔ Operating temperature 0-85C
✔ Compensates for bumps
✔ 2 Prototype PCBs Provided 3 PCBs
✔ Additional bonus goals
● Project was completed on time
● All specifications and bonus goals were met
● Customer is happy
✔ Has an inclination range of +/-80
✔ Has an accuracy of +/- 0.10
✔ Operating voltage of 5V +/- 0.2V
✔ Voltage outputs are ratiometric
✔ Voltage output from 0v to 5v
25. 2. Organizational Structure
● Brad Bauer - Team Leader, Accelerometer Specialist, Device Testing.
● Mohamud Jama - Software Communications and device selection.
● Tim Dirks - Software Algorithm and PCB verification.
● Abdiqani Sidow - Analog circuit and filtering.
● Komlavi Dagban-A - Primary PCB design.
26. 3. Description of Individual
Responsibilities
● Brad Bauer - Team Leader, Simulations, Parts Sourcing, and Accelerometer: Provide
assistance with implementing the software code to interpret accelerometer readings,
the digital interface with the microcontroller, and orientation on the PCB. Built final
display fixture.
● Mohamud Jama - Software Communication: Develop code allowing for ADC and DAC
communications with a resolution within design specs.
● Tim Dirks - Software Computation: Develop code for converting the output
accelerometer values into inclination readings with temperature and zero g offset
compensation.
● Abdiqani Sidow - Filter Design and Power Management: Design filters that provide a 1
Hz cutoff frequency while regulating current draw from the accelerometer. Ensure
standard power management practices are implemented and created Gant Chart
● Komlavi Dagban-A - PCB Board Design: Develop a printed circuit board with correct
footprints and proper traces that conform with suggested practices in the individual
component's data sheet.
