Requirements Specification for the Wireless Ski Timer
Wireless Ski Timer Group: David Pomeroy, Phil Da Silva, Nick Hnatiw, Mike Coughlin
Background:
Ski racing is a highly technical sport where hundredths of a second can mean the
difference between victory and defeat. Competitors in the sport are constantly finetuning their equipment and their technique in order to have the fastest time on race day.
Athletes spend a great deal of time training and testing equipment on practice race
courses. It is very helpful to time athletes during training so they can have direct
feedback about which combination of equipment and technique is most effective.
This document is the requirements specification for an electronics system to
accurately calculate the time it takes for a skier to traverse down a mountain. The timing
system is to be easy to use and inexpensive comparatively to timing systems currently
available. The system will be sold fully functional without any need to purchase any
more equipment.
Deliverables:
There are 5 major deliverables.
1. One working prototype of the electronics only (the design and packaging is
not part of the project).
2. The following manufacturing related artwork and documentation:
(a) wiring artwork
(b) drilling plan
(c) silkscreen and overlay
(d) parts list
(e) BOM
(f) Report detailing a manufacturing test plan and the associated analysis
3. User’s manual
4. System specification, including the design concept, block diagrams, functional
description of the blocks, system description, and any analysis done during
system design
5. Schematic diagrams and circuit descriptions
Principle of operation:
The ski timing system will consist of three units, a timing, start, and finish unit.
The start unit will be placed at the start of the race; this is generally the top of the
mountain. The finish unit will be placed at the end of the race, again generally at the
bottom of the mountain. The timing unit will be worn by the racer. The start unit will be
activated via an input from an external gating system. This activation will send a signal to
the timing unit. The signal will enable the timing unit to start keeping time in a
stopwatch fashion. The timing will be stopped by a signal from the finish unit. That
signal will be activated upon the input from an external gating system at the finish of the
race. The time will be calculated and then displayed to the user.
User Interface:
The user interface is divided between the start and finish units. Both the start and
finish units will have an external gate input, a buzzer, and an on/off power switch. In
addition the finish unit will also have a 4 x 16 character VFD, and a keypad with
functionality for ten digits, enter, escape, up, and down buttons.
Input:
The inputs are comprised of:
 A switch based input located on both the start and finish units. When
closed, a signal will be sent to the processor that will in turn send a signal
to the racer’s timing unit. If the timing has yet to start it will. If the timing
unit is currently keeping time, then it will stop and send its time data back
to the finish unit.
 A keypad on the finish unit will consist of twelve buttons. Those buttons
will include functionality for ten numeric, enter, escape, up, and down.
These buttons will be used for basic menu navigation.
 The finish unit’s antenna will require circuitry to allow communication
from the timing unit. They will communicate in the UHF range of
approximately 850-900MHz.
Output:
The outputs are comprised of:
 A 4 x 16 VFD display on the finish unit. This display will be the primary
means of communicating to the user. It will display a welcome message
on power up as well as allow the user to navigate the menu system for
result manipulation and to see results of each racer upon completion of
their race.
 A buzzer on both the start and finish units. The buzzer will emit an
audible sound that represents a start or finish gate has been tripped.
 Antenna on the start and finish units. The antennas will output a
frequency that will allow the timing unit to either start or stop its running
race time. This frequency will be in the UHF range of 850-900MHz and
will perform similar to that of RFID.
The User’s Manual:
Our timing system is in place to precisely measure the time it takes a skier to
negotiate the mountain. It will consist of three units. The first unit enables the timing of
the second unit. The third unit will disable the timing of the second unit as well as
calculate the race time and displays the results.
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Bring the starting unit to the start line, again which is generally at the top
of the mountain.
Bring the finishing unit to the finish line, again which is generally at the
bottom of the mountain.
Turn on both timing units by switching the “On/Off” switch to the on
position
Hook up external gates into gate ports on both star and finish units.
Allow racers to pass through start gate to enable timing unit worn by the
racer
Upon passing through the finish gate, total time will be shown for each
racer
Have good ski racing
Acceptance Test:
The performance test will be done at 6 levels
1.
2.
3.
4.
5.
Ensure timing units are reset and started properly at start gate
Ensure RFID system at finish units acquires total race time
Ensure that the units function properly under real world conditions
Test menu functionality
Run through field tests
Timer Reset
1.) During the reset process, we will test the logical levels of all signals involved,
i.e. making sure time registers are reset, by emitting a beep from a temporary
buzzer that will indicate a time values have been zeroed, and ensuring clocks
are powered up
Communication Testing
2.) During the transmission process, we will ensure signals from the processor are
correctly being output to the antenna and input to the antenna, by using an
oscilloscope. We then ensure the antennas are transmitting / receiving by
using a spectrum analyzer.
Real World Testing
3.) The units will be observed to be functional while applying extreme
temperature changes to the circuitry. The counter clock will be monitored
using an oscilloscope to ensure the correct frequency is output. Internal circuit
temperatures will be measured both in the lab and in average operation
conditions to evaluate nominal operating conditions.
Menu Testing
4.) Run through ever menu entry and sub entry and test input ranges to ensure
proper function.
Field Testing
5.) Nominally there would be a proper field test using actually operating
conditions. These conditions include temperature, elevation, and range.
Product Cost:
The end-product cost is approximately proportional to the cost of the parts. A
rule of thumb for a loosely estimated final manufacturing cost is to double the BOM. For
this reason the cost of all the parts of the entire system should be less than $250. This
would allow for a rough final estimate of the manufacturing cost to be approximately
$500. This is a convenient final cost for it is within the research budget and it allows the
retail price to be doubled to $1000. This allows a doubling of profits while keeping the
unit well under the current cost of similar products on the market to date. The retail price
can also be scaled back to allow the unit to be more attractive while still making an
acceptable profit.