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Mouse Droid based on Runt Rover Whippersnapper with Raspberry Pi

Currently travels programmatically, but will add ultrasonic navigation and autonomy.
AttachmentSize
Rover on the test bench.1.99 MB
Rover while still in the bag.146.29 KB

This is my first attempt a building a robot powered by a Raspberry Pi.

The base is a Runt Rover Whippersnapper by Actobotics. It was cheap and very easy to put together, and I wanted it to have 4 wheels. My idea was to basically build a Mouse Droid from Starwars, but I'm not interested in making it identical to the ones in the movies. I just want a small autonomous robot.

I was able to get the basic robot working with Python code I wrote myself by using:

  • a 2000 mA Powerbank (used for charging cell phones) to power the Raspberry Pi wirelessly.
  • Edimax Wifi dongle to connect to the Pi... though I may try and convert to Bluetooth in the future.
  • a L298 Dual H-Bridge motor controller to drive the motors.
  • 4, AA 1.5V batteries to power the L298.

This works perfectly and I am very happy about it. I was even able to get the servor working on a testing board, I just haven't connected it yet. I plan to add the PING sensor in the future for collision avoidance.

April 25, 2016:

I am trying to fix the turning problem by replacing the L298 with an Adafruit DC Motor Pi Hat. I'm just learning about all this and I had a couple of messages posted on the Adafruit board but I think I figured it out. With the Pi Hat which I accidentally bought from Robotshop when I was trying to buy the 16 Channel PWM Hat, I will be able to control 4 motors but no servos. So I'll have to get the PWM Hat to control any other servos it looks like. The hats are stackable, but I'll also need to order a taller header bus/thingy/doey to stack them properly.

Of course, I have practicaly 0 soldering experience and I want to practice a few small items first before I try and solder a GPIO header onto a $30 controller board.

Alternatively I might be able to use the PWM at with the L298, but I think the Motor Hat plus the PWM servo hat will make a better solution.

Please let me know if I'm completely screwing up here and if you have any better ideas please tell me!

Videos:

The built in video tool seems to not like my embed codes.

Rover moving back and forth: https://youtu.be/EtUPPmMu4y4

Rover failing to turn properly: https://youtu.be/CWzI2EXhmxQ

 

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The l298 is a great standby h bridge, but it needs a bit more power to overcome the voltage drop it has. I would use either a 7.4Fv Lipo/Li-ion or  at least 6 aa rechargeable nicad or nimh. You could use a https://www.pololu.com/product/2753. It has a lower vd. You may even want to ramp up Pwm to the motors for better control.  As for the pi gpio and pwm, it is iffy. If all you are doing is moving a sensor with it you should be fine. See here for more info where I do ithttp://www.instructables.com/id/Web-controlled-rover/

The tabs on those motors are really small indeed - when it comes to soldering, practice makes perfect, but start out with the right technique. Planning to add any more sensors?