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Topic: Need to power small dc motor car for specific distance and stop (Read 4 times) previous topic - next topic

GrisGris

Thanks for the input
This car is by far the most complicated. Others are fully mechanical, forced air, mouse trap etc.
Jim, Thanks for the links. We'll try those tutorials in class.
MaJ, thanks for the specifics thats our level of operation. I think we'll go with your suggestions.
I'm sure we'll have more questions in the near future.
Les Bon Ton Roulet

MaJiG

#16
Feb 12, 2013, 06:42 am Last Edit: Feb 12, 2013, 06:57 am by MaJiG Reason: 1
I am attaching a breadboard picture and a crude schematic, which has the motor connected to 3.3V as I believe you are using a 3V pager motor, yes?

You can have the students breadboard the project without the Hall Effect sensor like this:

*Run the wire from D12 to +5V to simulate the wheel being out of alignment.

*Download and run the code. The D13 (READY) should be OFF, indicating that you aren't ready to start.

*Move the D12 wire from +5V to GND, which simulates the magnet aligning. The D13 (READY) LED should come ON to indicate that the wheel is now aligned and we're ready to go.

*Press the GO button. The motor should start running.

*Now move the D12 wire between between GND and +5V ten times.

*After the tenth transition from HIGH to LOW (this number is a constant in the code), the motor should turn OFF.

You can test the setup and get everything working so that, when the Hall Effect comes in, you are already 90% done.  Be mindful of the heat of the motor.  It might not like running for more than 30 seconds or so.

The breadboard pic is generated by Fritzing here: http://fritzing.org/

GrisGris

Thanks MaJ
That's what we will do today.
The sensor is in the mail as of yesterday. 
I'll post back with our results tonight.
We'll probably have more questions too.
In the immortal words of Darnell Turner "That was a straight up Street Ballin move Willie."

MaJiG

BTW, you're going to need small powerful magnets. Like these http://www.amazon.com/Grade-Super-Strong-Neodymium-Magnets/dp/B001ANVAHI/ref=pd_cp_hi_1

They need to be axial. You would glue one with South toward the sensor and three with North toward the sensor.

Using four will balance the wheel and turn OFF the Hall Effect Detector, which is latching.

Willie the postman???

Keep me up updated...

GrisGris

OK we got the sensor and most of the circuit connected. We even think we understand what's going on. But here are our questions so far:
1. The code says D13 should have a LED to indicate ready but it is not shown in either diagram. We assume that the other end should be grounded but we are not sure of where to put it on the breadboard.
2. Our sensor has 3 leads the one in the diagram only has 2. According to the datasheet we think D12 should go to the output. The middle leg should go to ground and the input should should connect to 3V. Right? But again we are unsure of how to place it on the board.
3. Our go button is a spring loaded NO. Is that correct or does it need to operate in a closed position? 

Right, Willie the Postman... From the yard sale scene where Joy steals the ball from the game and Willie pops out his glass eye as a replacement.
My other favorite is Billie... "He can still be your brother, he just has to be an outside brother"
Thanks again for the help

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