January 30, 2013
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So I have had a few questions about if the Grand Prix / Pinewood derby track timer design or code would work on a Arduino. Well the short answer is no. Now that does not mean you can’t build a track timer with an arduino (I looked at them when initially consider the design) but there are a few reasons why (in my opinion) the Netduino is better in this situation. The most important is how the interrupt triggering works vs polling that you do on arduino.
If you want to know the “exact” time a car took to travel down a lane the resolution of that time is dependent on how small you can make the loop and that resolution can change if something else occurs on the arduino.
With the Netduino however you can set up hardware level interrupts on each of the input pins and those events have a timestamp from the hardware layer. Now it take considerable longer to process the events in the netduino but since you have that timestamp it is very easy to calculate the time elapsed. This allowed me to get to x.xxxx seconds vs x.xxx to x.xx seconds with the arduino.
Now some may ask if that is necessary and in response I will just give this example. In our first race after building the timer the final race was so close that on video you could not see a difference between the cars. Thier times were 3.1415 vs 3.1417.
If the time resolution was less than x.xxxx then this would have been recorded as a tie. Since using this system we have not had a single tie. This time resolution seems to fit the track we have which is 43′ long and only the first 10 to 12 feet has slope… if your track is shorter than that then you might need a higher time resolution.
Well I hope that helps. let me know if you have any other questions.
January 17, 2013
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Well it has been ages since I posted last but wanted to let any of you that might actually read this that I have found a couple of great places to get parts and supplies. For the last few months I have been running a Robotics club (based on the 3Pi Robot http://www.pololu.com/catalog/product/975)with some other fathers with kids around my sons age. We have done the line following, maze solving and are now moving on to much more advanced stuff like using an Ultrasonic Sensor and IR receiver. lots of fun.
Well one of the other father pointed me to a seller on Ebay called Chip_Partner http://stores.ebay.com/chippartnerstore and it is some Chinese group that sells electrical components dirt cheep and includes free shipping. So we needed 5 ultrasonic sensors and decided to give this place a try. Well for less than 12 dollars we had 5 of them shipped. It was supposed to take 2+weeks to arrive but 4 days later they showed up. Not sure how that works as this shipping would seem to cost more than that parts but it works. We have been using the ultrasonic sensors for a couple of months now with no issues.
The second place is Deals Extreme http://dx.com/. At first it just looks like another fake inline store that will just steal your money and if you ever do get it, it will not be what you wanted. However I realized that they have an entire section devoted to Arduinos and their stuff is super cheap (I mean cheap and not inexpensive). Some of it is clones of designs out there available for free on the web. what got my attention was this board: http://dx.com/p/avrmega328p-pu-development-board-for-arduino-152598 this Arduino has built-in Servo headers and is $16.60 US shipped. If you want to separate out the power for your motors the you can add this board: http://dx.com/p/l293d-motor-driver-expansion-board-motor-control-shield-blue-172881 it is only $8.80 US shipped so for about 25 dollars you can get 3 of the major components you would need to convert a old Remote controlled car into one controlled by an Arduino.
So I am going to order those 2 board and see if we have the same luck that we had with that Ebay group.