RE: Noise from flourescent light ballasts?
Timothy...very germane, very instructional. Thanks, Bob Heller 3M Product Safety, 76-1-01 St. Paul, MN 55107-1208 Tel: 651- 778-6336 Fax: 651-778-6252 == Christman, Timothy (STP) To: emc-p...@majordomo.ieee.org Timothy.Christman@gu cc: (bcc: Robert E. Heller/US-Corporate/3M/US) idant.com Subject: RE: Noise from flourescent light ballasts? 09/06/2001 03:22 PM Please respond to Christman, Timothy (STP) Not sure if this is germane to the list, but... Many newer fluorescent fixtures use an electronic ballast -- they use a switching converter or flyback to develop the high voltage required for the bulbs (laptop backlight elements work the same way). Apparently this reduces the amount of iron required for the ballast transformer (and $$$'s?), but has the unfortunate side-effect of creating a massive array of unwanted noise sources. Usually the switching frequency is designed to be just beyond the audible range, which is consistent w/ your description. As Richard noted, any switching / chopper circuit could be the culprit. The lights tend to pose problems for measurement/instrumentation circuits w/ high source and high receiver impedance (where capacitive coupling dominates) -- pretty intuitive when you consider that the bulb in the fixture has a large surface area at high potential, switching at KHz. frequencies. Timothy J. Christman Test Engineer Guidant Corporation 4100 Hamline Ave. N. St. Paul, MN 55112 USA www.guidant.com Opinions are mine, not those of my employer. My employer is evidently smarter. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: Noise from flourescent light ballasts?
Not sure if this is germane to the list, but... Many newer fluorescent fixtures use an electronic ballast -- they use a switching converter or flyback to develop the high voltage required for the bulbs (laptop backlight elements work the same way). Apparently this reduces the amount of iron required for the ballast transformer (and $$$'s?), but has the unfortunate side-effect of creating a massive array of unwanted noise sources. Usually the switching frequency is designed to be just beyond the audible range, which is consistent w/ your description. As Richard noted, any switching / chopper circuit could be the culprit. The lights tend to pose problems for measurement/instrumentation circuits w/ high source and high receiver impedance (where capacitive coupling dominates) -- pretty intuitive when you consider that the bulb in the fixture has a large surface area at high potential, switching at KHz. frequencies. Timothy J. Christman Test Engineer Guidant Corporation 4100 Hamline Ave. N. St. Paul, MN 55112 USA www.guidant.com Opinions are mine, not those of my employer. My employer is evidently smarter. -Original Message- From: wo...@sensormatic.com [mailto:wo...@sensormatic.com] Sent: Thursday, September 06, 2001 11:07 AM To: emc-p...@majordomo.ieee.org Subject: RE: Noise from flourescent light ballasts? We have experienced noise from variable frequency motor controllers used in air conditioning systems. There may also be some of these controllers in your factory controlling conveyer belts and other machinery. Richard Woods -- From: Chris Maxwell [SMTP:chris.maxw...@nettest.com] Sent: Thursday, September 06, 2001 11:38 AM To: EMC-PSTC Internet Forum Subject: Noise from flourescent light ballasts? Hi all, We have personally experienced an interesting phenomenon. We build a certain circuit that detects a 20Khz tone. This circuit is housed in a product that has an EMI spray coated case. One of our engineers noticed that our techs on the manufacturing floor were having a difficult time setting up units on the floor. The tone detect circuit kept getting set off for apparantly no reason. However, back in the engineering lab, we have no problems. So we did a little experiment. We took a unit out to the manufacturing floor and opened its case (which is how they work on them in manufacturing). We held it up near the lights. The tone detect circuit went crazy. We put the unit down on the bench. No problem. But, if you leave it opened up on the bench and hold your hand over the board, the circuit goes off again. When we close up the case work, all of these problems go away. So, our obvious solution is to make a modified casework with tweaker holes so that manufacturing personnel can tweak the amplifier pots with the casework closed. But I'm still curious. What's causing the interference? I was wondering if flourescent light ballasts could be giving off an emission in the KHz range. (Maybe that's why holding it to the lights sets it off.) But what about the hand waving? If I assume the ballasts are giving off emissions, can I also assume that the human body can change the local field pattern? Am I barking up the wrong tree? Maybe its the LAN cables in the ceiling? Anybody else have a similar experience or some insight into this? Thanks, Chris Maxwell | Design Engineer - Optical Division email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024 NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA web www.nettest.com | tel +1 315 797 4449 | --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site
Re: Noise from flourescent light ballasts?
Chris, Fluorescent tubes are noisy anyway, but the old passive ballasts are starting to be replaced with active electronic ballasts. Those electronic widgets actually run at frequencies down near what you're using. Electrically they can be EXTREMELY noisy. The US has no real restrictions. As far as what you observe, the hand can act as a shield, or as an enabler which would enhance a picked up signal putting it right into your electronics. What's important is that your circuit is very susceptible when exposed and not when closed. That implies marginality in your design. You should take a look at just how much you reject and whether that is adequate for your needs. - Robert - Robert A. Macy, PEm...@california.com 408 286 3985 fx 408 297 9121 AJM International Electronics Consultants 619 North First St, San Jose, CA 95112 -Original Message- From: Chris Maxwell chris.maxw...@nettest.com To: EMC-PSTC Internet Forum emc-p...@majordomo.ieee.org List-Post: emc-pstc@listserv.ieee.org Date: Thursday, September 06, 2001 9:22 AM Subject: Noise from flourescent light ballasts? Hi all, We have personally experienced an interesting phenomenon. We build a certain circuit that detects a 20Khz tone. This circuit is housed in a product that has an EMI spray coated case. One of our engineers noticed that our techs on the manufacturing floor were having a difficult time setting up units on the floor. The tone detect circuit kept getting set off for apparantly no reason. However, back in the engineering lab, we have no problems. So we did a little experiment. We took a unit out to the manufacturing floor and opened its case (which is how they work on them in manufacturing). We held it up near the lights. The tone detect circuit went crazy. We put the unit down on the bench. No problem. But, if you leave it opened up on the bench and hold your hand over the board, the circuit goes off again. When we close up the case work, all of these problems go away. So, our obvious solution is to make a modified casework with tweaker holes so that manufacturing personnel can tweak the amplifier pots with the casework closed. But I'm still curious. What's causing the interference? I was wondering if flourescent light ballasts could be giving off an emission in the KHz range. (Maybe that's why holding it to the lights sets it off.) But what about the hand waving? If I assume the ballasts are giving off emissions, can I also assume that the human body can change the local field pattern? Am I barking up the wrong tree? Maybe its the LAN cables in the ceiling? Anybody else have a similar experience or some insight into this? Thanks, Chris Maxwell | Design Engineer - Optical Division email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024 NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA web www.nettest.com | tel +1 315 797 4449 | --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: Noise from flourescent light ballasts?
Hi Chris, We have discovered that at least one fluorescent light product line has a circuit that operates at 34 kHz. Use or make a loop antenna and sniff your suspect area with your spectrum analyzer; then you will know for sure what the interfering frequency and source is. Good luck, Don Umbdenstock Sensormatic Electronics Corporation -- From: Chris Maxwell[SMTP:chris.maxw...@nettest.com] Reply To: Chris Maxwell Sent: Thursday, September 06, 2001 11:37 AM To: EMC-PSTC Internet Forum Subject: Noise from flourescent light ballasts? Hi all, We have personally experienced an interesting phenomenon. We build a certain circuit that detects a 20Khz tone. This circuit is housed in a product that has an EMI spray coated case. One of our engineers noticed that our techs on the manufacturing floor were having a difficult time setting up units on the floor. The tone detect circuit kept getting set off for apparantly no reason. However, back in the engineering lab, we have no problems. So we did a little experiment. We took a unit out to the manufacturing floor and opened its case (which is how they work on them in manufacturing). We held it up near the lights. The tone detect circuit went crazy. We put the unit down on the bench. No problem. But, if you leave it opened up on the bench and hold your hand over the board, the circuit goes off again. When we close up the case work, all of these problems go away. So, our obvious solution is to make a modified casework with tweaker holes so that manufacturing personnel can tweak the amplifier pots with the casework closed. But I'm still curious. What's causing the interference? I was wondering if flourescent light ballasts could be giving off an emission in the KHz range. (Maybe that's why holding it to the lights sets it off.) But what about the hand waving? If I assume the ballasts are giving off emissions, can I also assume that the human body can change the local field pattern? Am I barking up the wrong tree? Maybe its the LAN cables in the ceiling? Anybody else have a similar experience or some insight into this? Thanks, Chris Maxwell | Design Engineer - Optical Division email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024 NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA web www.nettest.com | tel +1 315 797 4449 | --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: Noise from flourescent light ballasts?
I read in !emc-pstc that Chris Maxwell chris.maxw...@nettest.com wrote (in 83d652574e7af740873674f9fc12dbaa675...@utexh1w2.gnnettest.com) about 'Noise from flourescent light ballasts?', on Thu, 6 Sep 2001: I was wondering if flourescent light ballasts could be giving off an emission in the KHz range. Yes, if they are high-frequency ballasts. (Maybe that's why holding it to the lights sets it off.) But what about the hand waving? If I assume the ballasts are giving off emissions, can I also assume that the human body can change the local field pattern? Yes. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Eat mink and be dreary! --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: Noise from flourescent light ballasts?
We have experienced noise from variable frequency motor controllers used in air conditioning systems. There may also be some of these controllers in your factory controlling conveyer belts and other machinery. Richard Woods -- From: Chris Maxwell [SMTP:chris.maxw...@nettest.com] Sent: Thursday, September 06, 2001 11:38 AM To: EMC-PSTC Internet Forum Subject: Noise from flourescent light ballasts? Hi all, We have personally experienced an interesting phenomenon. We build a certain circuit that detects a 20Khz tone. This circuit is housed in a product that has an EMI spray coated case. One of our engineers noticed that our techs on the manufacturing floor were having a difficult time setting up units on the floor. The tone detect circuit kept getting set off for apparantly no reason. However, back in the engineering lab, we have no problems. So we did a little experiment. We took a unit out to the manufacturing floor and opened its case (which is how they work on them in manufacturing). We held it up near the lights. The tone detect circuit went crazy. We put the unit down on the bench. No problem. But, if you leave it opened up on the bench and hold your hand over the board, the circuit goes off again. When we close up the case work, all of these problems go away. So, our obvious solution is to make a modified casework with tweaker holes so that manufacturing personnel can tweak the amplifier pots with the casework closed. But I'm still curious. What's causing the interference? I was wondering if flourescent light ballasts could be giving off an emission in the KHz range. (Maybe that's why holding it to the lights sets it off.) But what about the hand waving? If I assume the ballasts are giving off emissions, can I also assume that the human body can change the local field pattern? Am I barking up the wrong tree? Maybe its the LAN cables in the ceiling? Anybody else have a similar experience or some insight into this? Thanks, Chris Maxwell | Design Engineer - Optical Division email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024 NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA web www.nettest.com | tel +1 315 797 4449 | --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
Noise from flourescent light ballasts?
Hi all, We have personally experienced an interesting phenomenon. We build a certain circuit that detects a 20Khz tone. This circuit is housed in a product that has an EMI spray coated case. One of our engineers noticed that our techs on the manufacturing floor were having a difficult time setting up units on the floor. The tone detect circuit kept getting set off for apparantly no reason. However, back in the engineering lab, we have no problems. So we did a little experiment. We took a unit out to the manufacturing floor and opened its case (which is how they work on them in manufacturing). We held it up near the lights. The tone detect circuit went crazy. We put the unit down on the bench. No problem. But, if you leave it opened up on the bench and hold your hand over the board, the circuit goes off again. When we close up the case work, all of these problems go away. So, our obvious solution is to make a modified casework with tweaker holes so that manufacturing personnel can tweak the amplifier pots with the casework closed. But I'm still curious. What's causing the interference? I was wondering if flourescent light ballasts could be giving off an emission in the KHz range. (Maybe that's why holding it to the lights sets it off.) But what about the hand waving? If I assume the ballasts are giving off emissions, can I also assume that the human body can change the local field pattern? Am I barking up the wrong tree? Maybe its the LAN cables in the ceiling? Anybody else have a similar experience or some insight into this? Thanks, Chris Maxwell | Design Engineer - Optical Division email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024 NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA web www.nettest.com | tel +1 315 797 4449 | --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
