Mark-World - Tech Projects To Amuse The Curious
Robotic Arm
This robotic arm is controlled using a Raspberry Pi mounted just behind it and partly visible.  

Once a ball is detected the arm will fetch it and drop it into a box with one program I have written in python.  Another program runs a continual demo of moving balls from one place to another for a long running demo that does not need interaction but IS smart enough to adjust to somebody moving a ball.

Grabby is a Robotic arm that is both fun and interactive.   This robotic Arm has a gripper and a sensor to detect balls in different ways and allows smart activities like 'fetch' and more.
A short video showing this arm playing smart 'fetch'
Robotic Arm playing fetch in a  short Video

(The shaking has been fixed now but video is older)

A Raspberry Pi runs a python program for whatever mode is desired.  One mode is a sort of 'smart fetch' mode and another is a sort of ongoing demo that moves balls around from full to empty spots on a continuous basis that makes for a nice demo at robot shows.

The distance sensor is a VL53L0X mounted on my own 3D printed pieces on a mini Servo.  I call this a ToF (Time of Flight) Radar and have used this technique before to point the servo and measure a distance.  In this case I decide a ball is there if it is not too close or not too far and the resolution of the sensor is about 5mm or so.

The other servos for the arm itself are run from a Pololu servo controller that is commanded by the Raspberry Pi serial port and not over USB.  

The orange 'grabber' is driven by a mini servo that opens and closes the claw using a clever scheme where the servo rotates a disk that then pulls 4 fish lines, one from each finger, to then close or open the claw.

I designed and share a mini-servo holder used in this arm and the share can be found on for thing 2894532.  The gripper was also on thingiverse and I found it as thing 2303095

The metal parts for this arm were found on EBay and came with the main servos that control each joint.  This arm is said to have 6 'Degrees Of Freedom' which means 6 different things are separately controlled.

An older claw that came with the metal parts kit and was run as a demo using pololu software control is seen in THIS VIDEO
Robotic Arm