Shi Sen's robot arm using a Micro Magician
When I get some spare time I like to teach my son how to build things with Lego and K'nex blocks.He has some original K'nex blocks that I brought with me from Australia and a lot of "LoZ" blocks I have bought while in China. The LoZ blocks seem to be just as good a quality as the original K'nex.
I have been building this robot arm over about 3 weekends. Originally I did have it manually controlled using 3 levers to control the arm and gripper but it was very difficult to hold two levers in position while manipulating the third.
I decided maybe it was time to automate it using a Micro Magician robot controller. This allows the robot to be controlled using a cheap universal TV remote control and it can be powered with just 4x AA NiMh rechargeable batteries. Really it is not a true robot so much as a remote control toy right now. If I get time later I might give it an ultrasonic range finder and some other sensors.
The two main motors just have their control switch removed and the wires connect the motors directly to the two motor outputs of the Micro Magician.
The three motors controlling the arm have all been fitted with a control circuits from old servos that had stripped their gears. The 5K sensor potentiometer was replaced with two 2K2 resistors in series making them into continuous rotation servos. This allows them to plug into the Micro Magician controllers servo outputs and be powered directly from the batteries.
In this photo above you can see the servo control circuit fits neatly inside the K'nex motor housing. I have used my wifes hair bands to provide spring tension that helps support the weight of the arm and gripper. Two more hair bands are used to provide spring tension for the gripper which is controlled by two strings that run through the length of the arm to a motor between the wheels.
I have attached the code used in the video. In this case the robot uses an external IR receiver mounted on top of the robot. Although the Micro Magician does have a built in receiver the library does allow you to read IR receivers on any digital pin. This is useful when the control board cannot be mounted in a convenient location to receive a signal.