made up of a single
column of pulsating LEDs which when rotated will displays the text message.
360° Viewing Angle
The message can be
read from any angle around the rotating display horizontally and around
90° vertically.
The Message is Programmable
The unit's microprocessor
can receive data from an Infra Red link to update the message.
The Message can be
Scrolled
An I/R sensor detects
the drum position and synchronises the message scan. Thus creating either
a still or scrolling message.
3D
Display in Action
Jonathan Ashworth
was one of the Work Experience lads that helped
create some of the initial prototypes.
How
it Works
The Flash
Presentation at the top of this page shows how the single column of
LEDs describe the characters when mechanically rotated.
The eye's
persistence
of vision ensures that the previous LED positions are held in view
even though they've already changed.
A PIC16F873 Microprocessor
switches the column of LEDs on and off in sequence. The sequence
depends on the characters used in the message. The prototype software is
written in the 'C' Programming Language and is shown by CLICKING
HERE.
The software was
developed using Microchip's MPLAB-ICD software package. The photo below
shows the display unit connected to the ICD's pod which enables In-Circuit
Programming and Debug:
Unit
Design and Construction
The complete
prototype display demonstration unit consists of:
Display Unit
Prototype Motor Drive
Mechanism
Display Unit:
A microprocessor was
used for:
storing the displayed
message
storing the LED column
codes for all alpha-numeric characters -
Circuit Diagram of
the prototype can be viewed by CLICKING HERE
Hardware Construction:
Front
<- The Prototype PCB -> Back
Completed
Display Unit
The Display Unit's
main components are visible in the photo above:
PP3 9 Volt Battery
8 LEDS on the Right
2 Controls on the Left
for:
Message Select
Message Scan Rate
PIC Microprocessor
Chip between the 2 Controls
On/Off Switch at the
Top
6 Pin In-Circuit Debug
Connector just below the Switch
Prototype Motor Drive
Mechanism:
The Drive Mechanism's
main components are visible in the photo above:
Counter Balance Unit
Motor Drive Unit Prototype
using a 4" Cooling Fan.
Possible
Applications
Public
areas such as Train Stations and Airports where access to
information is vital. This form of display should reduce the congestion
of people crowding around the traditional 180° message panel.
Prototype
Development
The prototype
has passed it feasibility stage i.e. will it work? The next
stages of development will involve:
Constructing a more
rugged motor drive mechanism than the one described above.
The larger the display
unit's diameter the more characters can be displayed simultaneously. The
next prototype unit will be around 4 feet diameter.
The rotation speed
of the above drive mechanism needs to be increased to at least 600 R.P.M.
The message would then refresh 10 times a second which should reduce the
flicker
problem associated with running at low speed.
Developing the microprocessor's
software to include a complete character set.
Possible provision
for the descending characters: g,j,p,q and y.
The display unit will
have messages transmitted serially from a PC. This will be achieved using
a bank of I/R emitting and detecting LEDs across the gap between the fixed
motor and the rotating unit.
The onboard microprocessor
will interpret this information in the form of a 2 Byte Packet containing
Commands and Data. These can represent:
Selection of which
display unit (1 to 4 described above) the data relates to:
Selection of Character
Position on relevant display
The rate at which the
message is changed or moved. Used in message scrolling.
The motor drive unit
will be expanded to hold 4 display units giving a 4 row character display.
Message synchronisation
is achieved using another I/R sensor similarly described above. This detects
the drum position and synchronises the message scan. Thus creating either
a still or scrolling message.
