Hi All, I recently had looked at a case where a piece of equipment being tested for conducted RF immunity has some of its LEDs lit by the RF when the equipment was unpowered, which caused a test failure as the LEDs indicated a safety condition. The equipment had no power switch, when its function was needed, power was applied from another device. It means there is also a possibility of LEDs lighting in a powered-up device, not because the electronics are affected, but by the LEDs themselves lighting. Should we be testing RF immunity on unpowered devices?
This perked my interest and I have designed a small (2x3 inch board) for testing frequency response and sensitivity of LEDs to RF signals to 500 MHz. Just from the prototype, I see that LEDs vary quite a bit in frequency, some going to 500 MHz and beyond. I have also noted some conditions that affect the RF response, so I have built into my design a feature that makes the LED response independent of the characteristics of the amplifier furnishing the RF signal. The board schematic looks very simple, just five "components," but to implement the schematic takes about 15 real components to work properly.. This design and the problem LEDs can cause will be included in my class the third week of February (class is full of examples of strange problems in equipment and their solution). I will also host a web meeting next week, Thursday 9 am Pacific time, for those interested in this board design. Contact me privately if you are interested. The session is not free as I have invested a fair amount of time in the board design and construction which I will share during the meeting. Not sure yet what the fee might be, interested in input on this, but it will not be expensive. Doug [cid:[email protected]] - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> _________________________________________________ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
