Mechanical arm – home made robot

This mechanical arm is a manipulator with three degrees of freedom.

Mechanical part of the project and motors were made of metal elements from old wipers mechanisms and other components which can be easily found in almost every workshop. The motors from wipers are perfect for that project, because they have very high torque and large ratio. One of the motors was removed from a printer and is used for controlling the gripper.

There is an encoder, which counts pulses on each of three motors that move the arms. Encoders are necessary for determining the right position of the arms. There are also microswitches on each arm, which are used for determining the zero position after switching the supply.

Electronics was divided into two parts:

• PCB with executive elements
• PCB with control system

There is also a small keyboard.

Executive system:
Engines are powered by H-bridges (STA434A). The bridges are controlled by optocouplers, which protect the microcontroller against possible overvoltages and implement the logic of bridges control (so there is no possibility to give signals which could damage the bridges).

Control system:
Control system consists of microcontroller Atmega16, 2x16 LCD display, MAX232 for communication with a computer, operational amplifier for measurement currents of the engines, etc.

Program for Atmega16 allows you to control the robot:

• manual move each of arms and opening/closing the gripper
• speed adjustment (carried out with PWM)
• watching the current position and speed on the display
• remembering positions (up to 20 positions) + remembering the currently set speed
• remembering sequences (programs) of set positions (up to 10)
• looking for previously saved position with a possibility to follow the remembered points and looping the search

Using this robot, you can perform simple operations consisting of cyclic transfer of an object from one place to another.

Remembered positions adn sequences are stored in the EEPROM of the microcontroller, so after the robot is started, just reset the positions and you can carry out the remembered sequences.

Also current of the engines is measured to date. That provides indicating the overload.

Pictures:






Link to original thread (useful attachment) – Robot- mechaniczne ramię