Robotic Arm Controller From Homemade Conductive Paint

The goal of this project is to find an original and intuitive way to control a digital robotic arm made with the Processing program, using components that are compatible with Arduino. This consists of 5 different parts differentiated by colors. The first and the fourth can rotate (in both directions) up to 360 degrees and the others only up to 120 degrees.

In order to test its functionality, a game was designed in which the last piece of the robot has to touch a red ball, that changes its position as each game is completed. All this was initially controlled from the computer keys, but we had to find another way to meet the proposed objective.

That is why we have designed a prototype in which, by selecting each piece through pushpins that are connected to a circle of conductive paint, we can determine the position of each of them, by rotating a 3D piece with another pushpin on top of the paint.

The first thing that came to our minds was to make something tactile, but without the use of screens. That's why we investigated the different options we could use and discovered conductive paints. For this, we were inspired by the projects shown in the images, from which we came up with the idea of making a potentiometer from the paint, to control the angle of rotation of the pieces.

To control which piece we selected, we were inspired by the functioning of Makey Makey, which is based on different ways of creating open circuits that, when you touch them, being us ground, the circuit closes and the action is executed. However, we came up against the problem that everyone conducts current differently, so we had to standardize the contact between components with pushpins.

In this section, you can see how the different components are connected to the Arduino UNO. To make it easier to read, it has been explained element by element according to the function they play in the code and in the prototype.

For the prototype, we wanted to design a support that would allow us to hold the computer screen (we used a touch screen computer that could be folded 360 degrees) with the robot program incorporated, while at the same time having the robot controls all in the same object, imitating a bit the old videogame machines. That is why the support consists of two parts: the carcass and the part of the commands. For the first part, we used a 4mm thick MDF board to build it. This would not only have a specific space to place the screen, but also to store the different components needed to operate the robot.

Check if the paint is conductive before painting the diffuser. To test it, we recommend first drawing a line and, with a voltmeter and a wire connected to the arduino, see how much potential it drops. Then, we suggest to paint a line with the thickness you want for the panel (with two pieces of masking tape leaving the desired separation). And lastly, check if the perimeter of the circle is adequate to conduct and there is the necessary resistance (paint a circle of the desired diameter and thickness).

Thanks to this project, we have learned how to use conductive paints in order to create new types of circuits to control things like robotic arms. Also, it has enabled us to expand our knowledge of electrical circuits by playing with the concept of open or closed circuit to make the selection of each part of the robot.

At the same time, we have improved our programming skills by creating a code from scratch that executes this complex idea such as a potentiometer made of paint synchronized to a ring of LEDS, which as we have seen, the set is not always easy to calibrate due to the constant voltage variation it receives.

Another thing that we have found very interesting is to have controlled other types of programs that we already knew as Processing from Arduino, which shows us the infinite number of things that can be programmed with this simple and practical tool.

Although it has not been an easy project to execute, it has motivated us a lot to do it, because it has shown us that sometimes, no matter how complex an idea is, if you have the resources, effort and dedication necessary to do it, in the end it becomes a reality and with very good results.