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Sunday, 15 April 2018 19:29

Where to start?

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Question #1:  Where to start?

Well, if we're going to get something to move, we might as well start at the bottom of the "stack".  Given that FRC uses all DC motors (steppers and servos are for more precise motion control), we should start there as well. 

Since we are working with the RasPI, motors need to be smaller.  12VDC motors (without proper power protection) would fry the Pi. 

Fortunately, I happened to have an old Lego Mindstorm set I bought my kids when they were little (all the way back to the RSX...).  I found two Lego motors that should do well.

Of course the RasPi has lots of low power I/O capability (Digital Inputs/Outputs, UART, SPI, I2C, PWM), but not enough to drive multiple motors.  So, we're going to need a motor controller board.  We want something small that works well with the RasPi, but enough to drive motors at between roughly 3-6 VDC.  I chose this one from Adafruit

While I was at it, I ordered another Pi (I wanted to dedicate one to the robot and I'm using my first one).  I also ordered some standoffs (to keep the RasPi and the MotorHAT separate but well supported), a power supply and an SD card for the RasPi.  Between these new pieces and the left over parts I should have enough hardware to get started.

 

Just a note about power supplies...I'm going to start with all the pieces on a prototyping board, connected with two separate plug in power supplies, one for the RasPi, and one for the motors.  We need to keep in mind that eventually we need to be mobile. 

For the RasPi, I plan on using one of those tube like rechargable batteries that generates 5V (used frequenlty for cell phones), and a separate battery pack for the motors.  Probably a holder for 4 AA batteries.  That should give 6V for the motors, and separate 5V for the Pi.

OK, so parts on order, some parts on hand, time to think about software and how we're going to drive this thing around....

 

 

 

 

Read 19 times Last modified on Monday, 16 April 2018 16:36

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