Radiative immunity test. The Raspberry Pi is at the front right corner of the table. The video camera at the left is for monitoring output while the test is run
Electronics has its hazards in the form of electric shock, toxic fumes from components, fire due to short circuits, etc. Ideally, every component and equipment should be designed such that it poses no danger to its users. Various national or international standards are framed keeping in view the working environment and usage of the product. For every product, there are certain requirements to be met in order to ensure the safety of the users.
A background on international certifications
Every consumer electronics device that is commercially available in the global market has a certain mark on its back or side, such as CE or CCC, which shows the certification that it adheres to. Every country has a technical barrier, which is bureaucratically controlled to protect the local market or local imports. In India, we have the Bureau of Indian Standards (BIS) that sets the standards for the Indian region.
Kalyan Varma, head-India, TUV Rheinland, explains: “If you make a product that meets the entire Indian requirements, considering all the environmental conditions that we have in India starting from Kashmir to Kanyakumari, along with the BIS requirements, it would be a better product than what we get with the CE mark of Europe.”
While we do the design, we need other electronic components which we don’t produce by ourselves. We need to make sure that these components, which were bought from other suppliers, are also CE- and RoHS-certified. Otherwise, the whole designed part would not be allowed in the CE market
— Yu Yinsheng, general manager, Foryard Optoelectronics
Designing compliant products is challenging
Compliance testing assesses the electromagnetic compatibility (EMC) of the device and the electromagnetic noise generated by it. EMC testing ensures that products that have passed this test don’t cause interference to other products of the consumers and also don’t get affected by them.
Liz Upton from the Raspberry Pi Foundation explains how the Raspberry Pi got through CE, FCC regulation and C-Tick requirements: “The Raspberry Pi had to pass radiated and conducted emission and immunity tests in a variety of configurations (a single run can take hours), and was subjected to electrostatic discharge (ESD) testing to establish its robustness.”
• Standardization Testing and Quality Certification (STQC) Directorate
• Bureau of Indian Standards (BIS)
• Telecommunication Engineering Centre (TEC)
• Wireless Products Certification Wing (WPC)
• Central Drug Standard Control Organisation (CDSCO)
• Automotive Research Association of India (ARAI)
• Bureau of Energy Efficiency (BEE)
CE. It stands for ‘Conformité Européenne’ and is mandatory for products targeted at the European Economic Area. It is a declaration by the manufacturer that the product conforms to the EC directives.
FCC. Short for ‘Federal Communications Commission,’ it works towards six goals in the areas of broadband, competition, spectrum, media, public safety and homeland security. The FCC regulations are meant for the US market.
C-Tick. The C-Tick mark is intended for use on products that comply with EMC standards. It indicates that the product complies with the applicable standard and establishes a traceable link between the product and the supplier responsible for placing it on the Australian or New Zealand market.
CCC. It stands for ‘China Compulsory Certificate,’ and is mandatory for products targeted at the Chinese market. It is said to be one of the most difficult certifications, not because of the technical requirements but the difficulties related to the language of documents and compulsory on-site testing of manufacturing.
IEC 60950. This is an electrical safety requirement standard for IT and telecom products like laptops and phones. In India, this standard is known as the IS 13252 by the Bureau of Indian Standards.
Radiated immunity testing involves hitting the Raspberry Pi hard with narrow-band EM radiation while checking (amongst many other things) that the device is still able to send Ethernet frames to a hub. The first time the team did this, the light on the hub stopped blinking: no frames were making it through. They did it again but still nothing changed. Finally, they discovered that the hub (which gave every appearance of being CE marked, so it should have been able to get through these tests itself) was being knocked out every time somebody pressed the button,” Upton explains.
The team finally solved the issue by placing the hub outside the field, and the Raspberry Pi got through its immunity tests with no problem at all.
This shows that it’s not just the design but the components also that need to be robust. Yu Yinsheng, general manager, Foryard Optoelectronics, informs that CE and RoHS are the most common certifications that their products are designed for.
“While we do the design, we need other electronic components which we don’t produce by ourselves. We need to make sure that these components, which were bought from other suppliers, are also CE- and RoHS-certified. Otherwise, the whole designed part would not be allowed in the CE market. Now we have chosen electronic component manufacturers that we trust to be our partners,” Yinsheng explains.
In India, we recommend manufacturers, particularly embedded electronics services providers, to get some pre-evaluation done, as the failure rate, especially in EMC testing, is very high
— Kalyan Varma, head–India, TUV Rheinland
Challenges due to electromagnetic interference
Manufacturers, particularly those in embedded electronic services space, are recommended to get some preevaluation done, as the failure rate, especially in EMC testing, is very high.
“The first-time clearance is mostly like 10-20 per cent, as every product will have a certain amount of finetuning to be done. With pre-evaluation, you can have a better chance of higher pass percentage,” suggests Varma.
Pete Lomas, Raspberry Pi trustee and director of engineering at Norcott Technologies, led the team that designed the Pi. During the development of Raspberry Pi, Lomas says, the team was concerned that it would be an “open to atmosphere” design without the benefit of screening case.
“We designed countermeasures into the PCB from the outset. One decision was to use a full ground plane across the whole PCB to make sure that the ‘loop areas’ for potentially radiating signals were as small as possible. Decoupling was also important, and working on the advice of Broadcom engineers we placed these really close to the SOC power pins, which in this case was on the underside of the PCB directly below the processor and hence complicated the PCB design.”
“High-speed data lines, e.g., HDMI, were wired as differential pairs with matched lengths and carefully matched impedance. With all this in place, we were able to achieve a Class-A pass directly without PCB modifications. We need to do some modifications to achieve the more stringent Class-B and this work is ongoing,” adds Lomas.