[TriEmbed] Pinewood derby help

John Vaughters jvaughters04 at yahoo.com
Tue Jan 10 10:50:58 CST 2017


Craig,
Sounds like an interesting physics optimization problem. If I am reading this right. Still go down hill, but now you have a motor and not just gravity as a force. 
- When does the weight become a mass drag to the motor?- How to use the motor torque speed curves to find optimum gear ratio?- All the while trying to optimize acceleration within the race distance to make sure motor does not reach max speed and become a drag.- Keeping the car straight to not drag the edges by creating optimum weight distribution to prevent front back torque caused by motor drive.
I am sure there are more factors, but it sounds like fun to try to calculate the physics first and then test the ideas with all the great low cost sensors and computing devices we have these days. Or take another track and create a statistical study of design parameter method to find the optimum, or join the physics and study of design. 
All in All Great Fun!!!
The motor drive problem being the the easiest thanks to the great folks on this list. For me, I prefer the optical isolated drive methods, but that is because I am intellectually lazy and just use what works and is easy to do. It is always nice to see the talented folks on this list analyze this ever reoccurring question on motor drive circuits. I always learn more, every time it is brought up.
Let us know how you do in the competition and how the final design looked. 
Thanks,
John Vaughters

 

    On Monday, January 9, 2017 8:47 PM, Craig Cook via TriEmbed <triembed at triembed.org> wrote:
 

 That is very helpful.


Just changed my order to add some TIP120's.

The current motor has a .1 uF cap soldered to both terminals.

I'll make the changes you suggested.


Now I need to figure how how to add a "Micro Limit Switch Lever Arm Subminiature SPDT Snap Action" into the picture.  When the starting gate drops this should activate and turn everything on.  I'll be working on that waiting for my order.

Appreciate everyone's help.


Thanks

Craig

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