## 2 Chameleon-1 Helmet Design (Neuro-Electro)
### Full 3D Chameleon-1 Helmet  
The parts mentioned above make up the Chameleon-1 helmet (see Figure 4). The design features four bases, two front columns, four supports (two in each of the hemispheres), two motion planes, four weight distributors, two sensor bases, eighteen arms (nine in each hemisphere, grouped in three joints), four expansion mechanisms, twelve slots in the bases and columns, two rear columns, two expansion cylinders, and a protective case (see Figure 4a).  
Currently, there are different EEG devices, each of which stands out for one or more features depending on the model. In the literature, different shortcomings of the devices made were observed, among which the most recurrent is the size and fixed positioning. Some designs have limited expansion, while the design of the Chameleon-1 helmet expands like no other, managing to go from a small-sized helmet to a large one, in addition to incorporating the mobility system, this being the most innovative point of the EEG helmet.  
Current EEG helmet designs are limited to a specific size, have fixed electrodes, and are not very ergonomic. Some EEG helmets also have one or all three of the characteristics mentioned above. For this reason, an innovative design was developed that offers alternatives that can satisfy each of the needs that are lacking in the options that are developed or on the market with applications in the health sector.  
The developed EEG cap is designed to accommodate multiple electrode positions within the extended 10-20 system, including \(F_{3}\), \(F_{4}\), \(AF_{3}\), \(AF_{4}\), \(F_{1}\), \(F_{2}\), \(F_{5}\), \(F_{6}\), \(FC_{3}\), \(FC_{4}\), \(FC_{1}\), \(FC_{2}\), \(FC_{5}\), and \(FC_{6}\). These regions are closely associated with cognitive processes, making them highly relevant for studies on brain activity. This configuration allows for flexible electrode placement, ensuring comprehensive coverage of the targeted cortical areas and facilitating accurate signal acquisition. Four support units were implemented to distribute the weight of the Chameleon-1 helmet. These characteristics can be observed in Figure 4b.  
The four support units adhere to the skull and provide stability to improve the accuracy of the data obtained during treatment sessions in addition to efficiently distributing the weight, as seen below in Figure 5a. Different materials were used to build the helmet, such as polycarbonate, polyamide, polyester ether ketone (PEK), acrylonitrile-butadiene styrene (ABS), polyacetal, polyetherimide, fiberglass, carbon fiber, and galvanized aluminum.  
Figure 4: (**a**) Isometric view, (**b**) 3D isometric view of the Chameleon-1 helmet.  
The back includes an eight-channel \(OpenBC1\) electronic board that uses a PIC32 MX2 50F128B microcontroller, which samples at 250 Hz in each of the eight channels. The board is responsible for processing and storing the information obtained by the electrodes during therapy sessions. It also includes a protective casing whose main function is to protect the electronic board of the helmet, as shown in Figure 5b.  
The helmet has a mechanism that allows expansion without difficulty, while the protective box remains fixed and attached to the helmet. These configurations and characteristics of the Chameleon-1 helmet help to have a good reading of the signals, generating reliability and stability to avoid significant data losses.  
Building upon the developed design and addressing the limitations of existing headbands, efforts were focused on testing and characterizing the data obtained through the Chameleon-1 helmet. The following section provides a detailed analysis of this process.