# Testing of Indoor Obstacle-Detection Prototypes Designed for Visually Impaired Persons
## 4 Conclusions  
Following these comparisons and after discussions with representatives of the target group, the developed prototypes should possess the following characteristics:  
* User-friendliness. * High autonomy. * Low manufacturing cost. * Safety. The initial prototype is economical, comprising solely a micro-controller programmable board, an HC-SR04 ultrasonic sensor, a 3.5 mm audio jack module, and a power supply consisting of a 9V battery and its holder. The algorithm measures the distance between the prototype and obstacles based on multiple readings at 200 ms intervals. It determines the danger level for the user and transmits an audio message. In this prototype, the message is embedded in the code written on the micro-controller of the development board. The transmitted message can be personalized in terms of both language and voice tone, offering users the option to use their own voice. Subsequently, this new code will be written to the micro-controller of the prototype's development board. The primary advantage of this prototype lies in its manufacturing cost. Its components, especially if low-cost micro-controller programmable board clones are utilized, can be acquired for approximately EUR 12. Additional costs include the casing and battery. The drawbacks of this prototype include its size and the limitation that only someone with access to the source code can change the language of the messages. Furthermore, the necessity of the prototype connecting to the user's ear with a headset restricts its placement. The second prototype for indoor obstacle detection is similar to the first, but it uses recorded audio messages that are stored on an SD card. To read and write the audio messages on the SD card, it was necessary to include a read-write SD module in the prototype. The algorithm undergoes modifications; constants, preserving the messages transmitted by the PCM, are eliminated and replaced with a method that reads different wave files from an SD card that the user will hear. Additionally, the files must be copied to the root of the SD memory card and adhere to a specific naming convention. Utilizing files written on an SD card to alter the language and tone in which messages are transmitted presents a significant advantage. Essentially, swapping an SD card with messages in English with another with files in Romanian will automatically change the  
Figure 21: Materials second figure. language in which the user receives messages about the danger in front of them. This change requires no software knowledge or access. A significant disadvantage resides in the size of the prototype. Additionally, the connection to the headset remains a limitation. Although changing the language by changing an SD card is the most significant advantage, it is also a disadvantage in that the replacement of the SD card can be challenging task for a visually impaired person due to its size and the fact that the port is not reversible. As demonstrated by the tests conducted for these prototypes, the following conclusions can be drawn:  
* Static obstacles of square or rectangular shape placed in the user's direction of travel will be detected and, depending on the distance between them and the prototype, will be signaled accordingly. * The variation in the reading count between the PCM and WAVE prototypes arises from the duration it takes for them to \"speak\" and the algorithm's capability to automatically eliminate false readings. * Static obstacles of cylindrical shape are detected if the user is close to them, but at a greater distance, they may not be detected, or the distance between them and the prototype may be calculated incorrectly, leading to an incorrectly transmitted message. * Testing with different materials used as obstacles has shown that the 40 kHz sonic wave is not absorbed or reflected in a direction other than the correct one. * Under the conditions of very long usage of more than 9 h, the prototype can offer false readings due to overheating of the micro-controller.