Group SD0801

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Touchpad Testing Device

Group Members: From left to right; Kalana Maldeniya, Sarthak Ahuja ,Michael Benson

Advisor: Dr. Chao You

Client: Daktronics, Inc

Introduction

The project basically aims at building a device that checks the swim timing system used by Daktronics, Inc. Daktronics swim timing system has a touchpad that hangs at the end of each racing lane and indicates to the timing system when a swimmer has finished each lap. If the timing system malfunctions, it is necessary to be able to independently test the touchpad to determine whether it requires replacement.

Requirements

1) A visual and audible indication of actuation of the touchpad.

2) A force probe for measuring the force required to activate the touchpad.

3) An LCD screen for displaying the force of actuation.

4) A female DB9 serial port for updating firmware through a computer.

5) Design a battery power supply for the unit.

6) Use pulse width modulation to drive a piezoelectric buzzer through a micropin at the time of actuation of touchpad (audible indication).

7) Display the current applied force irrespective of the actuation of touchpad in another line on the screen.

8) Make the load cell submersible.

9) Use decoupling capacitors on the ICs.

10)Sleep the micro and turn off the LCD screen until the touchpad is actuated

Design Option

The device would have a sensing circuit that would sense a touch on the touchpad (i.e. change in capacitance). The output from the sensing circuit will be input to a microcontroller (PIC) to give visual and audible indications through an LED and a buzzer.

For measuring the actuation force an external force sensor will be used which will produce a current proportional to the force applied at the instant when a touch is sensed by the sensing circuit. The measured force will be displayed on an LCD screen using PIC. The following block diagram reveals the idea