gate-lap-timer | RACE ON! @ USC

Gate timer to measure lap time on race day.

Required Hardware

• Arduino UNO or compatible board.
• DFRobot 1602 LCD shield.
• Jumper cables.
• Laser source and detector pair (OR) ultrasonic rangefinder.

Software Prerequisites

• AVR-GCC toolchain
  • For Windows PC, install WinAVR.
  • For Mac OS, install CrossPack for AVR development.
  • For Linux, use the package manager of your OS to install the packages gcc-avr, binutils-avr and avr-libc.
• Arduino device drivers
  • The Arduino IDE is a reliable source for Arduino drivers.
  • You may also need to install the official FTDI VCP drivers.
• Terminal
  • The terminal in both Linux and Mac OS will suffice.
  • You could use CMD on Windows, but you could optionally also install MINGW. Git for Windows bundles git with MINGW - I personally prefer this approach when using Windows.

Operation Modes

We can either operate the gate timer using a LASER switch or an ultrasonic rangefiner.

LASER switch mode

In this mode, we are simply using a swtiching digital signal to detect the passage of a car and start/stop the timer.

• Connect the LCD shield to the Arduino UNO.
• Attach the detector (Active High) to Arduino digital pin 3 (AVR pin PD3). You may use jumper cables for this.
• Power both the LASER source and detector using the Arduino. Then connect the Arduino to a computer with all the prerequisite software installed.
• Using the command-lines (Terminal/CMD), navigate to the root directory of this project and run the command make laser to flash the correct hex file on to the Arduino.
• The board is now ready to use as a standalone gate timer.

Rangefinder mode

This mode uses the rangefinder to detect the passage of a car to start/stop the timer.

• Connect the LCD shield to the Arduino UNO.
• using jumper cables, attach the Rangefinder to the Arduino board.
  • VCC and GND go to the appropriate pins on the board.
  • Connect the TRIG pin of the rangefinder to Ardunio pin D13 (AVR pin PB5).
  • Connect the ECHO pin of the rangefinder to Arduino pin D12 (AVR pin PB4).
• Connec the board to a computer with all the prerequisite software installed.
• Using the command-lines (Terminal/CMD), navigate to the root directory of this project and run the command make rangefinder to flash the correct hex file on to the Arduino.
• The board is now ready to use as a standalone gate timer.
• NOTE: The trigger distance and reset distance for the rangefinder can be modified by changing the constants towards the top of rangefinder_gate.c, available in the directory ./test/rangefinder gate.
  • A new hex file can be generated using the make command. We must then replace the raceon_gate_timer_rangefinder.hex file in the root directory with the new hex file that is generated.

Using the Gate Timer

• First, ARM the gate timer by pressing the RIGHT button on the LCD shield. Without this step, the stopwatch on the gate timer will not function. This prevents spurious and false starts/stops.
• Now, when the car first passes the gate, the timer will RUN with the time updating on the LCD every second.
• When the car passes the gate a second time, the timer will go to STP mode and stop timing. Now the accurate time (accurate down to 1 ms) is displayed.
• To run the gate timer again, it must be armed once more - see the first step.

LICENSE

This project and all the code in it is distributed as-is and with no warranty under the GNU General Public License, Version 3. The included datasheets are distributed under appropriate licenses as specified by the manufacturer/publisher of said datasheets.