Richard, The circuit you describe would not be acceptable if your intention is to have the LEDs touchable by a person. This is because you have not provided adequate isolation between the source of hazardous voltage (230 Vac-rms mains) and an accessible part. The only capacitor type that provides any degree of safety isolation is an approved Y rated EMC filter capacitors; Y2 capacitors provide the equivalent of Basic Insulation and Y1 capacitors provide the equivalent of Double Insulation. In many parts of Europe the mains plug/socket combination is not polarised and so you have a 50% chance of plugging in your device only to find out that what you hoped would be the neutral (and so 'earthy' end) is in fact the 'live' end [of course, the 50% is only statistics and Murphy's Law says that the odds are far less favourable ;-) ]. Of course, if you embedded your whole circuit in transparent plastic which itself met the requirements for double insulation then that would be another alternative from an electrical safety perspective. Remember also that for Europe you would need to consider whether a single fault in your circuitry would cause the LED to emit levels of radiation in excess of the AEL for a Class 1 laser device per IEC/EN 60825-1. If it did then you would need to take steps to either eliminate that situation from occurring or you would need to ensure that the MPE for Class 1 would not be exceeded for any likely viewing condition. Not a complete list of issues, but probably enough to be getting on with... Regards, Richard Hughes Safety Answers Ltd
From: [email protected] [mailto:[email protected]] Sent: Tuesday, April 29, 2003 6:22 AM To: [email protected] Subject: CE and driving LEDs from mains I had a quick question about possible CE (and other problems) with an odd circuit for driving 1W and 5W white LEDs (350mA and 700mA) from 240VAC mains. What are you views on the following. Have 350mA LED(s) in series with 1000mF cap from +ve to -ve within full bridge rectifier. So far so good. -ve of bridge to mains N. +ve of bridge goes through a 4.7mF "motor start" rated capacitor to main L. Is this legal? Will it run foul of CE regs. How do I measure the power efficiency? Many thanks Richard This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
