Light-emitting diodes (LEDs) have become so prominent in so short a time that new standards and specifications are emerging faster than most engineers can gain familiarity with them. Prime among those are standards involving overcurrent and overvoltage protection from such organizations as the International Electrotechnical Commission (IEC), the Institute of Electrical and Electronics Engineers (IEEE), Underwriters Laboratories (UL), and the US Department of Energy's Municipal Solid State Street Lighting Consortium (MSSSLC), among others.
Experts say that most designers have a rudimentary understanding of the technical protection requirements for LED-based systems, but often need to be schooled on the details.
"Engineers know surge immunity," Usha Patel, director of the Latin American sales and segment marketing for Littelfuse Inc., told Design News. "They know they have to protect against lightning. They know they have to protect against inductive spikes. But there are areas where they still need to be educated."
The need to know involves many factors. Without protection, overvoltages and inductive spikes can damage sensitive electronics. And lack of understanding can cost money up front.
Patel, who has been involved with a DOE task force and other organizations on the creation of the specifications, suggests engineers familiarize themselves with the following standards:
Overcurrent protection for LED bulbs.UL 8750 addresses protection against the risk of shock and fire.
Overcurrent protection for LED luminaires. Key standards addressing the issue of overcurrent at the luminaire include UL 1598 and UL 1993, as well as UL 1310 and UL 8750.
Overvoltage protection for LED bulbs. Energy Star standards based on IEEE C62.41.2-2002 deal directly with surge suppression at LED bulbs. Outside the US, IEC61000-4-5 is the surge immunity specification for LED lighting.
Overvoltage protection for LED luminaires. DOE standards based on IEEE C62.41.2-2002 deal with surge immunity requirements for outdoor LED lighting.
Well, I won't go so far as to say that they are a racket, but....... they are not a non-profit organization. They have a bad reputation because of their poor customer service, yet if you pay them extra money for expedited testing you can still get the testing you need completed on schedule.
Some engineer colleagues of mine say that UL is a racket. They have toured some of their facilities, and found their practices and testing areas to be very unprofessional and ineffective. Once a company set out to protect consumers, now is just a company to absorb as much money as they can.
After hearing the stories, I have to pause and question any UL standard.
Some humanoid walking robots are also good at running, balancing, and coordinated movements in group settings. Several of our sports robots have won regional or worldwide acclaim in the RoboCup soccer World Cup, or FIRST Robotics competitions. Others include the world's first hockey-playing robot and a trash-talking Scrabble player.
A recent example of a major CAE revamp is MSC Apex, released last month by MSC Software Corp. In a discussion with Design News, MSC executives noted that its next-generation platform is designed to substantially reduce CAE modeling and process time, “in some cases from weeks down to hours.”
The Thames Deckway would run for eight miles close to the river’s edge, rising and falling slightly with the tidal cycle. It will generate its own energy from a series of devices that will line the pathway and use a combination of sources to make the path self-sustaining.
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