MEC202

Project Background and Objectives

Background: Existing public water dispensers have problems such as inconvenient operation, easy cross-infection, difficult water temperature adjustment, and insufficient lighting. Through the investigation of campus water dispensers, it was found that the touch screen water dispensers have low operation accuracy, and the key-controlled water dispensers have poor lighting around them, and the hot water overflow may cause scalds.

Objectives: Design a touchless smart water dispenser to achieve functions such as automatic filling, touchless operation, multiple water temperature mode selection, ambient light detection and illumination, and voice and screen interaction, so as to meet the needs of users to use the water dispenser safely and conveniently.

Planning and Division of Labor: The project is carried out in stages, including preliminary research, component purchase, function realization, assembly and debugging, and report production. Team members have clear division of labor and are respectively responsible for the realization of functions such as water temperature detection, pumping and voice guidance, bottle and water depth detection, screen interaction and illumination, and related report work.

Design Concepts

Automatic Filling Function: Three methods of realizing automatic filling, namely fixed water volume, measuring bottle volume and measuring bottle height, were compared. Finally, the method of measuring bottle height was selected because of its low cost and independence from bottle shape.

Touchless Control Function: Two methods of voice control and gesture control were analyzed. Considering that voice control is affected by noise in public places and has high cost, gesture control was selected to achieve touchless operation, and the APDS – 9930 gesture sensor was used.

Water Temperature Adjustment Function: Three water temperature adjustment methods of multi-tank water storage, outlet heating and adjusting pump speed were compared. Because the first two methods have high cost or potential safety risks, the method of adjusting pump speed was selected to achieve five water temperature modes (90°C hot water, 65°C slightly hot, 50°C moderate, 35°C slightly cold, 20°C cold water).

Ambient Light Detection and Illumination Function: Three schemes of timed lighting, sound detection lighting and ambient light detection lighting were discussed. Finally, the ambient light detection lighting method was adopted. The ultrasonic sensor was used to detect user approach and bottle height, and the gesture sensor was used to detect ambient light to achieve automatic lighting and energy conservation.

Voice and Text Interaction Function: Three interaction methods of buzzer and screen, indicator light and voice player and screen were compared. The combination of voice player and screen was selected to facilitate user operation and understand the status of the water dispenser.

Prototyping and Testing

Prototyping Method: A physical prototype of the water dispenser was built, and its overall framework and working process were introduced. Each function module includes bottle and water depth detection module (using HC – SR04 ultrasonic sensor and VL530X time-of-flight ranging sensor to determine bottle height and water level), gesture control module (using APDS – 9930 sensor to achieve gesture recognition and ambient light detection), water temperature sensor module (using DS18B20 digital thermometer to detect cold and hot water temperature), water pump module (using L293D chip to control two water pumps to achieve water temperature adjustment), ultrasonic and infrared sensing illumination module (using ultrasonic sensor to detect users and bottles, combined with gesture sensor to achieve lighting control), screen interaction module (using 2.8-inch TFT screen to achieve visual interaction) and voice command playback module (building an MP3 player to achieve voice prompts), and the circuit connection and working principle of each module were described in detail.

Test Results

Test of Bottle and Water Depth Detection Module: The height measurement test was carried out on three different bottles. The results showed that the measurement error of most bottles was within 5%, and the system had high stability; the test of the water level detection sensor also showed high stability and accuracy.

Test of Gesture Control Module: For the test of intermediate proficiency users, the recognition rate of the gesture control module reached 92.31%, and the recognition rate of skilled users was over 95%, verifying its effectiveness.

Test of Water Temperature Adjustment: The water temperature adjustment effect of the five water temperature modes was tested, and the results were basically consistent with the expectations. Although there were some temperature differences, they were within an acceptable range, proving the feasibility of the water temperature adjustment module.

User Feedback: Collected feedback from different user groups such as teachers, doctoral students and undergraduates. Most users recognized the touchless operationhe technology.