Difference between revisions of "S17: Propeller Clock"

Revision as of 03:31, 21 May 2017

Project Title

Propeller Clock (Persistence of Vision Based Analog Clock)

Abstract

Persistence of Vision (POV) refers to the optical illusion in which after image of an object seen by the eye, exists for a brief time, usually 1/10th of a second. We have used this phenomenon to create a POV clock where we display the face of an analog clock by driving one dimensional LED array (1 x 17) using precise time delays. To reduce the weight in order to achieve higher RPM necessary for POV displays, we have used wireless power supply modules to drive micro-controller and LED array which are located on the rotating arm.

Introduction

The main idea of the POV display is to flash/blink the LEDs at exact same location in each revolution. If the speed of revolution is fast enough, then the human eye cannot distinguish between two different blinks and the LEDs appear to be static and constantly glowing. Usually the motion picture frame rate is 24 frames per second and this seems to be an ideal condition for smooth POV system. However, anything above 10 updates per second can provide illusion of continuous motion.

In this project we have used 1200 RPM(no load) motor and have used 5mm bright LEDs (~10mA) which aid in creating a POV clock. Initially, the idea was to use slip ring to avoid mounting of SJOne Board on the rotating arm. However, RPM limit of 300 and limited number of wires on slip ring reduced it's feasibility. Hence, we mounted LPCXpresso LPC1769 board on the rotor and provided wireless power supply so that we can reduce the weight on the rotating arm by avoiding heavy battery. LPCXpresso LPC1769 board was chosen over SJOne board because of it's light weight and form factor which made it suitable for mounting on the rotating arm.

Instead of controlling the RPM of the motor and displaying the clock using fixed delays, we calculate and correct the time delay according to the varying RPM which in turn will compensate/nullify the effect of varying RPM on the display (moving/ dragging / stretching of the analog clock). For this, we have used reed switch.

Objectives

The main objective of this project is to implement the following:

• Determine the power consumption of the system especially the maximum current requirement so that it matches with the specified ratings of the wireless power transfer module.

• Design hardware system (PCB) which is fairly balanced and as light as possible so that it can be mounted on the rotating arm of the motor to provide balanced and stable rotation with sufficient RPM.

• Design precise time delays using timers interrupts to flash the LEDs at precise location.

• Design hardware and algorithm for compensating the change in RPM (to display a stable clock face - avoid rotation/dragging of clock face) using reed switch.

Team Members & Responsibilities

• Aakash Menon
  • Designing precise timer interrupts for providing timing base for updates in each rotation.
• Aditya Choudhari
  • Hardware and PCB Designing.
• Aditya Deshmukh
  • DC Motor Interface.
  • Reed switch/IR sensor interfacing and programming.
• Ajinkya Mandhre
  • Soldering the components.
  • Algorithm for displaying POV clock's hour/minute/second hand and final integration of all the codes.
• Kalki Kapoor
  • Algorithm that keeps track of actual time to be displayed.

Schedule

Parts List & Cost

Below is the bill of materials required in this project.

Design & Implementation

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Hardware Design

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Hardware Interface

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Software Design

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Implementation

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Testing & Technical Challenges

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My Issue #1

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Project Video

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Project Source Code

• Sourceforge Source Code Link

References

Acknowledgement

We would like to thank Professor Preetpal Kang for the knowledge he has given us about FreeRTOS and coding for bare metal ARM.

References Used

1. http://www.nxp.com/documents/user_manual/UM10360.pdf
2. http://people.ece.cornell.edu/land/courses/ece4760/FinalProjects/f2012/cfz4_sjh234/cfz4_sjh234/FinalProjectDocumentation.html
3. http://people.ece.cornell.edu/land/courses/ece4760/FinalProjects/f2013/js2839_yc969/js2839_yc969/js2839_yc969/index.html