Scott- I have seen some really simple circuits using common, cheap transistors that had unwanted oscillations in the range of 100 to 200 MHz, which failed radiated emissions.
The most recent one was similar to your circuit, though in the opposite direction -- a simple circuit with a few transistors driving the LED of an optocoupler for low speed digital data. The fix was simple (a small resistor in series with the base lead of the bipolar transistor driving the LED), but the test was essential, as the circuit otherwise performed without a problem. Don Borowski EMC Compliance Engineer Schweitzer Engineering Labs Pullman, WA, USA From: Scott Douglas <[email protected]> To: "[email protected]" <[email protected]> Date: 07/12/2013 06:46 AM Subject: EMC Required? Sent by: [email protected] Hi folks, Consider a simple circuit. IR diode, a transistor or two, some resistors and caps. Receives input from IR remote, converts to electrical and sends down a wire. No clock in the thing so you could call is passive. But does it need EMC testing for US or EU? The IR signal will be in the 35-50 kHz range so pulses down the wire will be the same. Does this make it fit within the realm of EMC required? The device is sold by itself without other products, but is always connected to something else in use. Something else could be a wide variety of anything. I think of it like a stand-alone audio speaker. Purely a passive device that is driven by signals that fall within the EMC required realm. So do you do EMC or not? Looking forward to your opinions on this. Scott - ---------------------------------------------------------------- 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 Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
