Hi All, I recently worked on a case where a conducted immunity RF test caused an unpowered circuit's LEDs to light up causing a failure. It turns out that LEDs can work well enough at much higher frequencies than one would expect. In addition to that, in the process of lighting up, a lot of harmonics are generated up to hundreds of MHz, at least. In fact, any non-linear element connected to a system cable will generate harmonics of an incoming RF signal, possibly causing radio interference. I have even seen corroded connections of wires do this and cause problems.
In the case of the LEDs, several tens of mA of RF current was available from the test and that interacted with resonances on the board. So, I am designing a board to evaluate LED RF sensitivity in terms of frequency response and amplitude of current. Should have it built soon. Seems like there is a need for such a device to allow designers to select the best part from suppliers. The board will include a current monitor with frequency response from DC to at least 500 MHz and will also gauge the possibility of EMI generated by the LED under test. The board, its design, and the background of the issue will be added to my class in the third week of February. Eventually I will publish this later on, possibly at DesignCon 2024 or another venue in 2024. 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
