Thursday, June 7, 2012

Arduino Sandwhich 2: The Sea Perch

The Sea Perch Arduino Sandwhich sits in a similar Otter 2500 box on the bow of the Sea Hawk.  Its stack is only three boards high for now.

As with the Sea Hawk sandwhich, an Arduino Uno R3 forms the bottom layer. It also needs its own power source (a 9 V battery through the barrel plug; note that the battery is in a separate Otter Box and note that you don't want to use a normal 9 V battery brick because it won't last long enough for the mission and when it starts to get weak the logic will go crazy and your robosub won't behave properly. Use a NiMH hobbyists 9V battery pack!)

The second part of the stack is the ADAFRUIT MOTOR SHIELD whch comes in a kit from Adafruit and which you will solder together yourself.  It is the only inexpensive motor shield we know that can handle up to 4 motors and 2 servos, making it ideal for the Sea Perch.  Note that the Adafruit Motor shield needs its own battery source, which should be an 11.1 V to 12 V hobby battery.  Make sure you remove the jumper on the shield so that you  isolate the power from the Arduino board because you DO NOT want to power the motor shield from the Arduino power supply!

 ONCE AGAIN: MAKE SURE YOU REMOVE THE JUMPER ON THE JUMPER PINS  SHOWN ABOVE SO THAT YOU CAN USE A SEPARATE POWER SUPPLY FOR THE MOTORS AND A SEPARATE POWER SUPPLY FOR THE ARDUINO. The Adafruit Shield comes with the little black plastic jumper in place here and this would make both the Arduino and the Motor Shield use the same power supply (either plugged in to the terminals on this shield or into the barrel jack of the Arduino).  The problem with this is possible motor noise interference and erratic behavior on the part of the Arduino.  Safest is to remove the jumper so your Adafruit Shield looks like ours in the picture above.   You can read more about the topic here:
The top of the Stack is an Xbee shield. We recommend the one from Sparkfun because it plugs right into the stackable headers and will work (should work!) right out of the box without any configuration or wiring.  It draws its power from the Arduino board and once you  have loaded up our "running the Sea Perch from the computer keyboard" sketch onto the Arduino and you plug the Xbee USB dongle into your computer  and open the serial monitor in the Arduino IDE it should work as though you are connected to the board, only wirelessly.

With this configuration you should be able to pilot your Perch wirelessly from your laptop, safe and dry on the shore!

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