Silkrip ORR Computer Owner s Manual Silkrip Motorsports LLC Rev H 4/13/2017 IMPORTANT CHANGE TO SENSOR WIRING! Tom King The latest version of the Owner s Manual is available under the Services tab of the www.silkripmotorsports.com website 1
Contents Introduction... 3 Unpacking Your Silkrip ORR Computer Unit... 3 Installation... 3 Terminal Strip... 6 Basic... 7 What if I Want Changes?... 7 Glossary of Terms... 7 Operation... 8 Preset Waypoints for Silver State Classic Challenge and Nevada Open Road Challenge... 9 What About Two-Way Courses Like BBORR?...10 Preset Waypoints for Big Bend Open Road Race...10 Log...11 Advanced Section...13 Mileage Factor...13 Target Speed...13 Waypoints...13 Calibrating Your Crystal...14 Coarse Calibration...14 Fine Calibration...14 Calibrating Procedure...15 Source Code License Process...16 Motorsports can be dangerous. Use of this product without a navigator can cause distracted driving, and this is especially dangerous in high speed rally events. The manufacturer assumes no liability for any incidents that may occur during competitive driving events or at any other time. 2
Introduction Thank you for purchasing the Silkrip Motorsports ORR Computer. This manual is divided into two sections: Basic and Advanced. The Basic section describes how to operate the device in an ORR competition. The Advanced section describes how to change the source code to optionally configure your own waypoints and target speed and initial mileage factor. Unpacking Your Silkrip ORR Computer Unit The Silkrip ORR Computer comes in a custom box containing the following items: Computer Cable with keyed connector at one end and unterminated at the other Hall-Effect sensor with cable Two rare earth magnets (CAUTION: pinching danger; also keep away from electronics) In-line fuse holder and fuse GPS antenna Terminal strip Spade lugs Red wire and black wire (for + 12V battery connections) USB 2.0 cable Male A Male B, 6 feet (optional for connecting to PC) Owner s Manual The Computer has a cap over the GPS antenna connector (on the left side of the unit as you are facing the front of the Computer). You can remove this protective cap if you are going to use the GPS antenna. Note that the GPS antenna is often not needed in order to pick up the GPS signal at the start line. Also, the LED displays have a protective sheet which may be removed. Installation Install Hall-Effect speed sensor in front right wheel (see pictures) Install two magnets in front right wheel (use RTV rather than epoxy to glue the magnets); make sure the south pole of the magnet (marked) faces the Hall-Effect sensor Install in-line fuse on 12VDC line from battery Mount terminal strip under hood, connect wires to terminal strip (see diagram) 3
Run cable from inside cockpit through firewall to terminal strip and connect wires (see diagram) Mount computer securely in cockpit (not in an airbag path!) Connect cable to computer (see picture) Although there are a number of imaginative ways of mounting the Hall-Effect speed sensor, one of the easiest ways is on the back side of the disk brake dust shield up high. The sending unit may also be attached to a strut or any other part of the car that maintains its distance from the rotating wheel. 4
Route the wires along the brake line and then inside the front (usually engine) compartment. Mount the two magnets to the wheel 180 degrees apart with the marked side (south pole) facing toward the Hall-Effect sensor. Leave 1/8" to 1/4" of gap between the Hall-Effect sensor and the magnets. Use RTV rather than epoxy or super glue to mount the magnets because the RTV has more flexibility and is not as susceptible to brittle separation. CAUTION: The rare earth magnets supplied with the computer system are VERY POWERFUL and can cause injury if they slam together pinching a finger. 5
Terminal Strip Main cable has a round connector on one end (computer end) and is unterminated on the other end. Push the unterminated end from the cockpit through the firewall to the front compartment (often the engine compartment). Then use spade lugs to terminate the wires onto the terminal strip as shown below: Brown wire pulses from sensor Orange wire - gnd Red wire Sensor Power Yellow wire +12V Green wire from sensor (pulses) Black wire from sensor (ground) Red wire to sensor ½ amp fuse + 12 Volts from battery Ground from battery NOTE: A spade lug is normally attached to a wire using a crimper, but it is a good idea to solder the spade lug to the wire after crimping; this is because crimping is not always secure enough. 6
Basic Your target speed is pre-loaded into the computer based on your purchase specifications. The computer also comes with a default set of waypoints for the Silver State Classic Challenge events on Nevada Highway 318 or with a default set of waypoints for the Big Bend Open Road Race in Texas. It also comes with an initial mileage factor that changes dynamically during the event; the initial mileage factor is either a default value or is based on your specification of your front tire make, model, and size. What if I Want Changes? Change Service from Silkrip (target speed, waypoints, initial mileage factor) nominal fee Purchase a second Arduino Uno computer and have Silkrip program it and send it to you for mounting inside the original Silkrip ORR computer system Use the Advanced section to do the changes yourself using a PC and your purchased Source Code License Glossary of Terms Target Speed Your selected target speed for the event (e.g., 120 mph) Waypoint A defined point along the course with a known mileage from the start Mileage Factor The number of 100 millionths of a mile covered by each ½ revolution of your front right tire (e.g., a mileage factor of 60,000 means 0.00060000 miles or 3.168 feet) Mileage The number of miles from the start, shown in thousandths of a mile Ahead-Behind Time The amount of time you are ahead or behind your target time; the computer shows this in hundredths of a second on a continuous basis; note that a minus sign indicates you are behind, whereas no sign indicates you are ahead. Precision The resolution of the computer s measurements (e.g., a distance resolution of about 3 feet, and a time resolution of 1/100 second) 7
Accuracy The absolute accuracy of the computer s measurements (e.g., how close the distance measurement is to the real distance, and how close the time is to the atomic clock time) NOTE: The Silkrip ORR computer is quite precise and accurate in its time measurement, but it is only precise, not accurate, in its distance measurement. The lack of distance accuracy is due to tire expansion. However the Silkrip ORR computer compensates for this tire expansion inaccuracy by dynamically re-computing the mileage factor based on waypoint inputs along the course. Arm/Clear The switch to the right of the red Mark pushbutton is the Arm/Clear switch. When it is over to the right, it is Clear; when it is over to the left, it is Armed, ready for a pushbutton input. The yellow LED indicates Armed. Mark The red pushbutton on the left side of the computer is used to mark waypoints, including the start and the finish, as you travel down the course. The red LED indicates you have marked a waypoint, and you must Clear and then Arm before the next waypoint; this prevents multiple interrupts to the computer when you mark a waypoint. Power The switch on the far right is the Power On switch. The green LED shows power on. When the green LED is blinking (usually a minute or so after power on), it means the computer is picking up the Pulse-Per-Second time signal from the GPS satellite and is therefore able to compensate for the start line delay. Log After the finish AND BEFORE TURNING POWER OFF, you can continue to use the Arm/Clear and Mark buttons to read the log of your results at each waypoint; this is a circular buffer, so you can cycle through the log as many times as you like before you turn power off. Operation Turn power on before reaching the Start Line; note that there may be a 1 2 second delay before the LED displays light up Make sure the Arm-Clear switch is in the Clear position Top LED display shows Ahead/Behind Time in seconds and hundredths of a second Bottom LED display shows mileage to the thousandths of a mile Ignore the initial readings prior to the start; note that the software resets the Ahead/Behind time if it goes beyond about 320 seconds. THIS MEANS THAT THE COMPUTER WILL NOT BE USEFUL IF YOU GET MORE THAN ABOUT 5 MINUTES AHEAD OR BEHIND WHILE ON THE COURSE! 8
Green power light will begin blinking if the GPS receives the atomic timing signal; otherwise, the computer will still function but there will not be any reaction time compensation at the start. Put the Arm-Clear switch in the Arm position; the yellow LED will light. When the atomic clock display at the start shows your start time, push the red pushbutton. Make sure you do this within less than a second of your start time! The computer will automatically record your start time as the beginning of the second, thus compensating for your reaction time and the raster scan delay time of the atomic clock display (assuming the green power light is blinking). The red LED will light. NOTE: If you mistakenly hit the red pushbutton a second early or a second late, you can still compensate for this by targeting to be a second late or early at the finish. Don t worry - this is quite rare, and it is not fatal to your chance to trophy. After you get under way, switch the Arm-Clear switch to the Clear position when convenient. Both the yellow LED and the red LED will go out. About a mile or so before each waypoint, move the Arm-Clear switch to the Arm position. The yellow LED will light. At each waypoint, push the red pushbutton. The red LED will light. Move the Arm-Clear switch to the Clear position when convenient. The computer will adjust its mileage to the waypoint mileage, with a corresponding change in the Ahead-Behind time. At certain waypoints, the computer will automatically recalculate the mileage factor to adjust for tire expansion. The waypoints near the finish are the most critical! If you miss one, just leave the computer alone, don t make any further inputs, and use the Ahead-Behind time to guide you across the finish line. Preset Waypoints for Silver State Classic Challenge and Nevada Open Road Challenge Mileage Waypoint Description 0.000 Start 9.400 County Line Sign 36.600 Beginning of Guide Rail on right after Flag Station 4 at Notch Mountain 66.445 White River Narrows large wooden sign on stone platform on right 84.426 Curves sign just before the triple curves leading onto the final straight 88.019 Mail Summit Rd sign on right at crest of hill on final straight 90.000 Finish Line 9
What About Two-Way Courses Like BBORR? Just use waypoints on the way back, not on the outbound leg. For the outbound leg, start the computer as normal at the start line and also start your stopwatch. At the finish of the outbound leg, record your stopwatch time and calculate your ahead-behind time. Then on the inbound leg, use the computer and your waypoints, but compensate for your outbound ahead-behind time (e.g., if you were 5.3 seconds early crossing the outbound finish line, target to be 5.3 seconds late crossing the inbound finish line as displayed on the computer s Ahead-Behind display). Preset Waypoints for Big Bend Open Road Race Note: The strategy for BBORR using the Silkrip ORR Computer is as follows: 1. Arm, push the Mark pushbutton at the southbound start; also start your stopwatch 2. Use the Silkrip ORR Computer s Ahead/Behind time as a rough guide as your make the southbound run 3. Stop your stopwatch upon crossing the southbound finish line; determine how far off ideal time you are. 4. Turn power off the Silkrip ORR Computer, then power it back on in preparation for the northbound leg 4. Compensate for your southbound time differential in your northbound leg (e.g., if you were 5 seconds fast in the southbound leg, aim for 5 seconds slow at the northbound finish line as shown on the Silkrip ORR Computer Ahead/Behind time display). Northbound BBORR Waypoints Mileage Waypoint Description 0.000 Start 8.790 Downie Draw Sign end of tire warmup 31.080 Ft Stockton 30 sign 51.770 Ft Stockton 10 sign 57.800 Blue Adopt a Highway sign 58.500 Reflector at windmill 59.000 Finish Line 10
Log When you push the Mark pushbutton at the Finish Line, the mileage display freezes at the final recorded mileage, and the Ahead-Behind display freezes at the final time difference. Do NOT turn power off the computer. At this point (perhaps in the Finish Pits), you can access the log and write down the results at each waypoint. Clear, then Arm, then push the Mark pushbutton. The Ahead-Behind display will typically show a small negative number (e.g., -0.39) that represents the delay time the computer has added for the reaction time and raster scan delay time back to the beginning of the second of the atomic clock. The Mileage display will show a (relatively meaningless) number that is the distance you traveled between turning the computer on and the start. Clear, then Arm, then push the Mark pushbutton again. The Ahead-Behind display will display the number 0 (actually 000.00) to indicate that this is the start waypoint. The Mileage display will display the initial defaulted Mileage Factor (e.g., 60.000) just ignore the decimal point. Upon the next Clear, Arm, Mark sequence, the Ahead-Behind will show the ahead or behind time at the next waypoint (e.g., -0.97 seconds) PRIOR TO CORRECTING THE MILEAGE TO THE WAYPOINT MILEAGE. The Mileage display will show the miles at the waypoint (e.g., 9.356) prior to the computer correcting the miles to the waypoint miles. Upon the next Clear, Arm, Mark sequence, the Ahead-Behind will show 000.01 to indicate waypoint number 1 (the start was waypoint number 0), and the Mileage display will show the Mileage Factor. Continue reading the log values in this manner, writing down the results. 11
Here is a typical log: -000.39 002.347 000.00 060.000-000.96 009.359 This is just a tire warm-up section, no Mileage Factor recalculation 000.01 060.000 001.73 036.440 000.02 060.355 Note that the mileage factor changed dynamically this is the new mileage factor calculated at waypoint 2.* 008.33 066.459 You were about 8 seconds ahead at this waypoint 000.03 060.326 Mileage factor changed again, this time downwards -000.34 084.420 000.04 060.346 The Mileage Factor bumps back up again somewhat 000.02 088.017 000.05 060.346 The Mileage Factor is NOT recalculated here -000.09 90.001 Finish Line, less than 0.1 second off! 000.06 060.346 Again, the Mileage Factor is not recalculated here *Note that the Mileage Factor recalculation starts from the 9.400 waypoint to the 36.600 waypoint, disregarding the tire warm-up section from the Start to the 9.400 waypoint. New Mileage Factor = Old Mileage Factor x (Official Waypoint Difference/Measured Waypoint Distance) 12
Advanced Section By purchasing an optional source code license from Silkrip Motorsports LLC, you have access to making your own changes to the source code using a PC and downloading the revised code to the computer. Mileage Factor Although the Mileage Factor is adjusted dynamically, you may want to start with a close value based on your log results of prior runs. Here is the line of code to modify: volatile long MF = 64556; // Mileage Factor 0.00064556 miles per pulse Target Speed Here is the line of code to modify: int targetspeed = 120; // This is for a target speed of 120 mph Waypoints The system comes programmed with 7 waypoints (numbered 0 6). If you want to change just the waypoint miles, here are the lines of code to change: int WPMiles[7] = {0, 9, 36, 66, 84, 88, 90}; // These are the whole miles int WPThousandths[7] = {0, 400, 600, 445, 426, 19, 0}; // These are the thousandths So the pre-programmed waypoints are 0.000, 9.400, 36.600, etc. 13
If you want to change the NUMBER of waypoints, things get more complicated. For example, if you want to change to 8 waypoints (adding one at 72.614 miles), here are the lines of code to change: int WPMiles[8] = {0, 9, 36, 66, 72, 84, 88, 90}; int WPThousandths[8] = {0, 400, 600, 445, 614, 426, 19, 0}; boolean finishflag[9] = {false, false, false, false, false, false, false, true}; boolean RecalcFlag[8] = {false, false, true, true, true, true, false, false}; boolean startacc[8] = {false, true, true, true, true, false, false, false, false}; int logab[16] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; int logm[16] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; int logt[16] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; if (lognumber > 16) Calibrating Your Crystal The crystal oscillator in the Arduino Uno processor daughter board attached to the Silkrip ORR Computer main board will typically have a built-in error, either too fast or too slow. This affects the timing. Therefore, each Silkrip ORR Computer is calibrated prior to shipment with a coarse calibration to compensate for most of the error. And starting with the Revision H software, there is also a fine calibration built in to the software to tune out most of the remaining error. Coarse Calibration At the end of the Setup portion of the Source Code listing, there is a line of code like this: Timer1.initialize (9998); // this creates a 100 Hz timer signal calibrated 9998 for unit n The number shown in parentheses in this example 9998 is the coarse calibration. If you change it by one, it will make the real time clock slower or faster by about 0.01%. Fine Calibration In the Initial portion of the Source Code listing, there is a line of code like this: int crystalcomp = 39; // this varies by CPU and compensates for the CPU crystal error over 90 miles In this example, the number 39 is the fine calibration for the crystal. In the Loop portion of the Source Code listing, there are these lines of code that use this fine calibration: if (waypoint == 0) // if this is the Start 14
{ (actualtime = GPScount + (crystalcomp*(120/targetspeed))); // set the actual time back to the start of the GPS PPS signal // but compensate for the fast crystal in this Unit 2, which is 32 centiseconds at 120 mph over 90 miles (ABTime = 0 - GPScount); // log the starting GPS count The fine calibration number is thus adjusted for your target speed (with 120 mph as nominal) and then added to the delay time at the start from the time you push the pushbutton back to the actual start of the GPS second. If the fine calibration number is negative, it will get subtracted from the delay time. Calibrating Procedure Using the Silkrip Test Station, bench test your Silkrip ORR Computer at a target speed of 120 mph. Use an accurate stopwatch to time the result. Adjust the stopwatch results for GPS delay, finish line deviation, and the final ahead/behind time at the finish of your test. Then change the fine calibration number to make the adjustment. For example: a) Starting with a crystalcomp = 0, suppose your test results (from the log) over the 90-mile course of Highway 318 look like this: GPS delay = 23 (i.e., 0.23 seconds from GPS start to pushbutton at the start) A/B Time at Finish = 0.50 seconds Distance at Finish = 90.011 miles Stopwatch Time = 45:00.250 b) Adjust the stopwatch time as follows: 45:00.250 + 0.230 = 45:00.480 This is your reaction time at the start 45:00.480 (30 x 0.011) = 45:00.480 0.330 = 45:00.150 This is the extra time beyond the finish line at 120 mph; i.e., you were late pushing the pushbutton at the finish. 45:00.150 0.50 = 44:59.650 This subtracts the ahead/behind time at the finish. c) This means you need to change the crystalcomp to -35. 15
Source Code License Process Pay for and sign the Source Code License Install the Arduino IDE on your PC or laptop Set up the port and attach the USB cable between the Silkrip computer and your PC s USB port Download and install certain specified libraries to augment the standard Arduino set Create an Arduino Sketch with the Source Code listing Compile the Sketch Download the Sketch Modify the source code to suit your needs Compile the modified Sketch Download the modified Sketch and test it (note that you can buy a test kit including a speed simulator and test cable from Silkrip Motorsports LLC) 16