EMC and heat development in a kiosk application

Background

Our EMC and thermal experts were approached by a company that had developed a kiosk application. Although the application seemed to function correctly, significant exceedances of the CE standards were measured during EMI tests. These exceedances posed a risk to the surrounding systems.

Problem Identification

Upon further investigation, it was found that the kiosk contained various adapters for the printer, cash dispenser, computer, monitor, and network switch. These adapters were placed close together in a connector block at the bottom of the kiosk, generating significant heat. This heat buildup caused the internal temperature of the kiosk to rise quickly.

To address the overheating issue, the designers had considered installing a fan. However, due to the poor quality of the fan power supply, this idea was ultimately abandoned.

Design Challenges

Although the kiosk's touchscreen functioned well, there were minor grounding issues. Additionally, the internal computer was placed above the adapters, causing it to draw in preheated air. This design negatively impacted the lifespan of the electrolytic capacitors in the embedded computer. The display, placed above the computer, was also affected by the heated air. Since this display was located on the outside of the kiosk, the extra heat was particularly undesirable.

ESD and EMI Issues

ESD tests further revealed that several connectors were insufficiently grounded, occasionally causing image disturbances. A cost-driven choice for a network filter contributed to leakage current, causing the application to exceed EMI measurement standards.

Solutions

Through a series of simple adjustments and the replacement of two components, the kiosk application was modified to comply with all CE standards. These adjustments included:

1. Repositioning power adapters: The adapters were rearranged to reduce heat buildup.
2. Improving grounding: The grounding of connectors was improved to prevent image disturbances.
3. High-quality power supply: The power supply and network filter were replaced with higher-quality alternatives.

Results and Future Improvements

The adjustments resulted in a kiosk application that met all CE standards. Additionally, the likelihood of malfunctions was significantly reduced, leading to fewer on-site repairs and a substantial reduction in service costs. In future developments, the importance of thorough EMC and thermal management will be incorporated earlier and more prominently in the design process.