Very cheap idea! I
Very cheap idea! I like!
Quite simple to compared to the others.
Now I’m tempted to go buy a pedometer just to hack it and see what I can do.
Using acceleration is an
Using acceleration is an interesting idea. I think you can use the euation for calculating velocity from constant acceleration, v=v0+at, where v is velocity, v0 is original velocity, a is acceleration and t is time. If you sample the acceleration from your accelerometer every second, you can “pretend”, that the acceleration is constant for that second until the next sample. Of course this is inaccurate, but you can increase the accuracy by increasing the sample rate.
Don’t know if this makes sense or is at all correct.
Well, with sampling, I’ve
Well, with sampling, I’ve always been told to sample at double the speed. Looking at how long strides are on skates as my base, I’d want to sample 2-3 times per second, which would imho be accurate enough for me.
I also need to figure out storing things in eeprom so that if the batteries die I still have my data. Ideally I’d like to take the distance in each minute, and store it. That way I can tell when my fastest minute is, average speed, etc.
2-3 times per second should
2-3 times per second should be enough, if you put the accelerometer on yourself, because your body wont be accelerating as much, but you will be moving the skates back and forth a lot, so they will have a lot of accelerating and decelerating and may need more samples.
I think the final design
I think the final design will use accelerometers. The only thing I have to figure out now is an easy way to get all the information saved on the chip to either a text file or into an excel sheet.
I really wish I had paid more attention to computer programming instead of just hardware…
Some of the PIC18 chips have
Some of the PIC18 chips have USB support, so if you use that, you should be able to hook it up to your PC and download the data. The data can be stored on a I2C eeprom. On the PC, you should have a program that can read the data and save them to a file. Read all values (time, acceleration, speed, position etc), separated by a ‘,’. Each line should be separated by a CR/LF. This file, you should be able to import into Excel.