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USB Interfaced Force Sensor

USB Interfaced Force Sensor. By: Byron Roberts John Campbell Sean Larkin. Project Objectives. Interface sensor with computer. Sensor must convert an analog signal to a digital signal. Sensor output displayed on screen. Complete project as soon as possible. Facilitate group learning.

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USB Interfaced Force Sensor

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  1. USB Interfaced Force Sensor By: Byron Roberts John Campbell Sean Larkin

  2. Project Objectives • Interface sensor with computer. • Sensor must convert an analog signal to a digital signal. • Sensor output displayed on screen. • Complete project as soon as possible. • Facilitate group learning

  3. Materials Used • Flexi-force Sensor • MSP430 Micro-controller

  4. The Sensor • Tekscan FlexiForce sensor • thin • durable printed circuit makes up the sensor element • allows easy integration to many different areas. • Sensor detects and measures a change in force • determines the rate of change in force • detects force thresholds • identifies contact.

  5. Computer Interface Hardware • Texas Instruments MSP430 Microcontroller • Mixed-signal microcontroller • 16-bit CPU • Low power consumption • MSP430F2xxx series • Operating frequency 16 MHz • Voltage Range 0-3.6V • 14-pin JTAG connection • USB interfaced

  6. Computer Interface Software • IAR Embedded Workbench • Freeware code compiler and debugger • Supports 30 different processor types • Supports C programming

  7. Setting up the Software • Project -- Options • General Options • Target – Device • MSP430F013

  8. Choosing the right library • General Options • Library Configuration • Library -- CLIB • Taking up less memory • General Options • Library Options • Printf formatter -- Small

  9. Setting up the debugger • Debugger -- Setup • FET Debugger • Using the right drive • FET Debugger • Setup – Connection • Texas Instrument USB-IF

  10. IAR Sensor Program #include <msp430x20x3.h> #include <stdio.h> int i; void main(void) { WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer P1DIR |= 0x01; // Set P1.0 to output direction SD16CTL = SD16REFON + SD16SSEL_1; // 1.2V ref, SMCLK SD16INCTL0 = SD16INCH_1; // A1+/- SD16CCTL0 = SD16UNI + SD16IE; // 256OSR, unipolar, interrupt enable SD16AE = SD16AE2; // P1.1 A1+, A1- = VSS SD16CCTL0 |= SD16SC; // Set bit to start conversion _BIS_SR(LPM0_bits + GIE); } #pragma vector = SD16_VECTOR __interrupt void SD16ISR(void) { printf("%d\n", SD16MEM0/1291); }

  11. How it Works • TekscanFlexiForce sensor • Piezoresistive sensor • Meaning? Voltage directly related to force?

  12. How it works (cont.) • resistance is inversely proportional to the applied force and the conductance

  13. The circuit adjust in paint

  14. Set up • Simple set up • USB connected • Add weight • Readout on screen • keeps track of data collected • Gives digital actual weight readings

  15. Problems encountered • MSP430 not easy to program • Software integration with windows 7 • Surface area of sensor • Calibration difficult

  16. Applications of Force Sensors

  17. Future of our project • Digital read out to LCD display actual weight. • Send data to excel to make graph and permanently store the data • Extra portable scale

  18. References • http://www.intersema.com/docs/intersema_brochure_en.pdf • http://static.technorati.com/10/09/02/17535/oilrig3.jpg • http://www.futek.com/apps_load.aspx

  19. Thank You • Questions?

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