Xref: utzoo misc.consumers:4845 sci.electronics:2923 Path: utzoo!mnetor!uunet!husc6!uwvax!oddjob!ncar!gatech!udel!princeton!phoenix!jmsulliv From: jmsulliv@phoenix.Princeton.EDU (John M. Sullivan) Newsgroups: misc.consumers,sci.electronics Subject: Re: fluorescent lights and my brain Message-ID: <2814@phoenix.Princeton.EDU> Date: 8 May 88 04:21:30 GMT References: <530@scourge> <1182@ssc.UUCP> <1532@dataio.Data-IO.COM> <1143@neoucom.UUCP> <9890@ism780c.UUCP> Reply-To: sullivan@fine.Princeton.EDU (John M. Sullivan) Organization: Princeton University Department of Mathematics Lines: 49 Keywords: eyes head ache electricity I am posting this for my brother, Charlie Sullivan, who doesn't have access to e-mail. I will, however, make sure that he gets replies you send to me at sullivan@fine.princeton.edu John Sullivan --------------------------------------------------------------------- I work for a company, Lutron Electronics, that makes lighting controls, including high-frequency fluorescent ballasts and other products that can help people who are presently unhappy with fluorescent lighting, particularly near VDTs. My understanding of the issue of whether or not 120 Hz flicker is visible is that pure 120 Hz is not visible, at least not to most people, but that any small amount of a 60 Hz component in the fluctuation of light level is very easily visible and annoying. This can be caused by any assymetry between the two halves of the 60 Hz cycle. 60 Hz flicker is often most visible in the ends of the lamp, as they switch between being anodes and cathodes. Miswired fixtures, bad lamp socket connections, bad lamps, and combination air conditioning vents/light fixtures ("air handling fixtures") all contribute to increasing visible 60 Hz flicker. The filaments in the end of the lamp are normally heated to make them emit electrons to act as cathodes. If one end is not heated, it will not work as well when it is supposed to be a cathode, and the whole lamp can act somewhat like an old vacuum tube diode, and be brighter in one half cycle than in the other half cycle. One product our company makes is a high-frequency fluorescent ballast called Hi-lume. It operates above 20 kHz so that it is inaudible. It is also more efficient than a normal 60 Hz ballast. (The lamp itself produces more light and less heat than it would at 60 Hz, and a 60 Hz ballast has considerable losses in the resistance of its windings, and in the hysteresis of the magnetic material.) The >40 kHz pulsation of light is much too fast to be visible. Hi-lume is also capable of controlling the light level from 100% to 1/2%, which is good for setting a comfortable light level for working at VDTs. It is available in 120 and 277 volt versions, and for a variety of lamp types. Although there is never any visible flicker, there is some 120 Hz variation in light level. (The circuit was designed to do that to improve power factor.) An older version, identified by model numbers beginning with PCU instead of OSPCU, has no light level fluctuation below 20 kHz. We also have other products for controlling light level of fluorescent lamps which can be very helpful for reducing eye-strain for VDT users. Although Hi-lume gives the best dimming performance, other products include such things as systems that allow using normal 60 Hz ballasts to to minimize rewiring and installation trouble and cost on retro-fit instaltions. For more information you can call our hot-line at 800-523-9466 or 800-222-4509 in PA.