Deep Touch Pressure Abdomen Belt Group 32 Kevin Rathbun & Luke Fleming & Chang-O Pyo ECE 445 Senior Design April 28, 2015

Introduction  Automated, remote controlled belt with air pump  For autistic children, simulates a squeeze  Helps teachers control students  Improves focus and reduces anxiety in autistic children

Features  Remote control with settings for both pressure and time  Air pump on timed schedule  Pump to different levels depending on the child  Low-cost, easy to use  ~5 inch wide flexible belt made of neoprene

The Belt Velcro Air tube for pumping

Old Block Diagram  Excluded Valve control  Nonspecific power supply design  Removed LED indicator / Added 7-segment display

Block Diagram Pump/ Valve

The Remote PCB 3V to 5V Converter Transmitter and Antenna 7-Segment Display Headers

The Remote Module Features  Includes 7-segment display for pressure strength (0-3) and timed pump (0-9)  4 switches for choosing pressure, time, deflate, and send signal  Transmitter and antenna sending data at 418 +/- 3 MHz

Remote Module Power Supply  3V battery power supply  Boosted to 5V using 3 to 5 converter  Transmitter required 3V while rest of components required 5V 3 to 5 Boost Converter Circuit

3V to 5V Boost Converter Schematic

3V to 5V Boost Converter Plots/Tests

Remote Module 7-Segment Display, Microcontroller, and Switches 4 push button Switches Microcontroller ATMEGA328P 7-Segment Display with LED Drivers

Original Hardware Design (Microcontroller)  To operate the ATMEGA328P on the breadboard, a 16MHz Crystal and capacitors are required Original Microcontroller schematic

Revised Design (Microcontroller)  16MHz crystal and and 2 x 22pF capacitors were added on the circuit Revised microcontroller schematic

Original Hardware Design (Seven segment Display)  Common-cathode lines on seven segment display connected to 3V supply instead of ground  Each LED driver shares STCP and SHCP signal from microcontroller instead of having separate signals Original 7-Segment Schematic

Revised Hardware Design (Seven Segment Display)  Seven segments are connected to ground  Separated STCP and SHCP signals on microcontroller Revised 7-Segment Schematic

Software Requirement for Remote  Read input from 4 switches  Control seven segment display  Send 8-bit data (time & pressure) to transmitter

8-Bit Data of Pressure and Time  Microcontroller can output 8-bit serial data output data = x x x x | y y y y  First 4-bit(x) : Pressure strength (0~3) : 0000~0011  Last 4-bit(y) : Duration(0~9) : 0000~1001  Ex) if user sets pressure to 3 and time to 9, then output data =

Software Requirement for Belt  Read data from receiver  Read data from sensor  Process data and control motor with valve

Flow Chart of Remote Module  Time and pressure switches make increments of each values  Each value is converted to 8-bit data for 7-segment display  When start switch is pressed, data is sent to transmitter

Flow Chart of Belt Module  Code records received data  Code processes both received data and pressure sensor data  Control outputs for motor and valve with processed data

Programming Challenges (Original Code)  Delay function puts microcontroller to sleep  In sleep, it can’t read new data Serial Monitor of Belt Module (Original)

Programming Challenges Overcome (Revised Code)  Millis function allows microcontroller to multi-task  Can read new data during operation Serial Monitor of Belt Module (Revised Code)

Receiver-Transmitter Specifications  Receives digital data from microcontroller at 9.6 kbps  Transmits data at 418 +/- 3 MHz  Receives that data at 418 +/- 3 MHz  Converts received data back to digital for microcontroller

Receiver-Transmitter Plots/Testing  Digital waveform input to transmitter at 4.8KHz, created by waveform generator  Output of Transmitter/Input of receiver  Output of receiver

Main Belt PCB Motor/Valve Control Receiver/ Antenna Voltage Regulator

Main Belt Features  Receiver and antenna, receives data at 418 +/- 3 MHz and converts to digital signal at 4.8Kbps  Motor control for inflation and solenoid valve control for deflation  Voltage regulator  Force sensor

Main Belt Voltage Supply  Batteries supply 6V for running the motor at maximum operation  Voltage regulator reduces to 5V for the microcontroller and force sensor  Diodes drop voltage to 3.3 +/- 0.3V for receiver

Main Belt Motor Control Original Design  Original design included a H- bridge for motor control  Expecting inflation and deflation capabilities Hex-Bridge schematic

Updated Main Belt Motor/Valve Control  Simpler design utilizing a BJT as a switch  Same circuit for both valve and air pump Air Pump/Valve control

Force Sensor  Original design included a pressure sensor  Force sensor testing after demo  Larger fluctuations in voltage compared to pressure sensor (0-1.5V versus mV) Force sensor voltage readings, 200mV divisions over 15 seconds

Hardware Failures  Boost converter couldn’t supply enough current  PCB design flaws  Antenna range  Broken pressure sensor

Future Work  More efficient PCB design  Low power indicators  Bluetooth/Transceiver chip  LCD display for more user friendly interface  Phone App to replace remote control

Thank You