This paper seeks to address design ethics, going beyond traditional approaches and focusing on socio-technical systems instead of on individuals. It investigates some issues that affect the ethical interests of designers as professionals, together with technological and environmental issues that have not received much attention from ethicists. The methodological framework combines the Value-Sensitive Design (VSD) developed in computer ethics with the methodology based on need, requirements and performances developed in architecture. This approach is applied to the development of connected appliances, dealing with problems in a positive and proactive way. Some guidelines are drawn at the end of the dissertation to achieve this purpose, establishing responsibilities and limits of the designer in the design process.