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Robotics is accessible to everyone and moreover it is simple to control. However, special attention should be paid to certain technical aspects. And more particularly to the handling of servomotors.

The project uses readily available components. Once the components are assembled, they will be coordinated by a micropython program with the Thonny application.

A previous version of this project was driven by arduino-IDE. The new generation of microcontrollers gives a new direction to projects and programming. The micropython language seems to me easier to use and in particular the Thonny interface. Of the three published articulated arm automation projects, this is the most successful.

The robot is an articulated arm that moves on three axes and is driven by 6 servomotors.

The particularity of the program is to be able to memorize the successive positions of the arm.

We can then ask the program to place the arm successively in the positions recorded as visible on the video. For the video only 7 positions have been memorized.

The program is responsible for smoothing the movement.

The positions will remain stored when the power is off.

Everything is controlled using a smartphone using a Bluetooth app.


Articulated arm kit

The complete articulated arm kit can be found for less than $50. Unfortunately if the mechanical parts are of good quality, the servomotors (MG996) are not. During the tests two servos burned out. They have been replaced by more expensive but robust DS3225MG servos. Mounting the arm does not pose any particular problems. Having noticed that screws were unscrewing under the effect of vibrations, I recommend adding self-locking washers.

Raspberry pico

A latest generation controller from the Raspberry family.

Bluetooth HC05

Easy to program module.

Power supply

The power supply must be efficient and allow current peaks of up to 2.5 amps. The display of the current consumption makes it possible to control the drifts. For example, in the event of a servomotor blocking, the current will increase sharply and the voltage may decrease below 4V, which may cause erratic movement of the servomotors. A visual control of the power supply becomes essential.

Android App

To control the arm, a smartphone or tablet with the “Bluetooth Remote” application will be used. This free application is simple to configure. It is based on the creation of programmable buttons. For each button, a sequence of characters to be sent via Bluetooth is defined. The Arduino equipped with the HC05 module will receive the information to transform it into actions.

EEPROM memory

The arm memory consists of a module containing an AT24C256 or AT24CXX Eeprom. This memory is used to keep the information after the model is turned off. This information is available after reboot. This module is connected in I2C.”

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