[TriEmbed] Pinewood derby help

[John Vaughters]

> I hadn't considered the motor actually slowing the car down though.
It wouldn't really slow it down, but it would prevent it from speeding up, or become a dragging force once you reach the top RPM the motor will run with the applied load at the top voltage. It is a significant force to consider. The extreme example would be a 100:1 gear ratio on a motor. You get to top speed quickly, but just try to speed it up with another force, it is difficult. The motor and gear leverage is the limiting factor.
Probably the best sensor you could use would be an acceleration sensor. Then you could play with the gear ratio that gets you to a constant acceleration and top out near the finish line. It would be fairly clear that you top out with the sensor. Between the best time and acceleration measurements you will find the best gear ratio. Also, consider ramping the voltage with your PWM to prevent wheel spin. If you really want to go all out and do not care about the motor, test over driving the motor with higher than rated voltage. They can take it, but only for so long before they spark themselves short.
Good Luck and Have fun!!!! 

    On Tuesday, January 10, 2017 12:56 PM, Craig Cook via TriEmbed <triembed at triembed.org> wrote:
 

 >Still go down hill, but now you have a motor and not just gravity as a force.

Correct.

If I can make it work I also want to be able to ssh into the CHIP when at the race track so I can make tuning adjustments.

Race day is 27 Jan.

It's going to be a power-to-weight and traction problem.  I hadn't considered the motor actually slowing the car down though.


If there is interest I could do a TriEmbed presentation on "How I made a block of wood into a Race car with the help of TriEmbed".

My Son's car is going to have LED headlights and tail lights.  That is run from a CR1616 battery I already had.  Will be run in a parallel circuit with resistors.  Already have that working on a breadboard.  Fitting 5mm LED's into a block of wood and hiding wires is interesting.  I sacrificed a cat6 cable for it's wiring.



Got a note today that my digikey order has been shipped.


Thanks

Craig

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