JohnRoss Posted June 30, 2009 Share Posted June 30, 2009 Interesting fault in that a 9W high efficiency bulb which we keep on in the hall so visitors can find the loo at night has started flashing when it is turned off. The circuit has a switch with an incorporated neon which is wired across the switch and lights up when the switch is in the off position, return path through the lamp it controls, so you can find it in the dark. When the switch is on the neon is shorted out. What I think is happening is that the high efficiency neon filled lamp is effectively in series with this indicator neon and ionises at regular intervals giving the brief flash. I assume the current through the neon indicator is not sufficient to keep the 9W going and so it goes out and the process starts again. I don't know if this is in any way dangerous but I assume that disconnecting the neon in the switch would be one solution. Has anyone else had this?..................................................JR Link to comment Share on other sites More sharing options...
Nick Trollope Posted June 30, 2009 Share Posted June 30, 2009 Suggest you read the advice I gave you on TF.I still reckon that it is not the lamp (per se). Link to comment Share on other sites More sharing options...
JohnRoss Posted June 30, 2009 Author Share Posted June 30, 2009 Ok Nick and thanks for both replies. I don't think it is a fault with the lamp either as I tried a couple of spares and they were the same. If I fitted an ordinary filament bulb it does not do it as the impedance of the ordinary bulb must be much lower than the neon high efficiency lamp except when it strikes I guess. As these type of switches are common and neon high efficiency bulbs are becoming so you would think that lots of folks would have noticed this effect. Another circuit with a different arrangement and where the lamp is not visible from the switch i.e. where the switch neon only comes on when the light is on and not off, wired between the lamp side of the switch and neutral I guess, also tend to glow when the light is switched off if using a high efficiency lamp but not a filament type. Could this be leakage across the switch do you think or some sort of induction? Ain't technology wonderful!...................JR Link to comment Share on other sites More sharing options...
Dave&Olive Posted June 30, 2009 Share Posted June 30, 2009 hi ok I read something a few months ago about low wattage lighting and 2 way switches , but cannot find it on the net now ... It went on about low wattage lights glowing dim when fitted with 2 way light switches ....... Nick back to you on this Dave Link to comment Share on other sites More sharing options...
JohnRoss Posted June 30, 2009 Author Share Posted June 30, 2009 Found this http://www.sciencefile.org/cgi-bin/yabb2/YaBB.pl?num=1226927074/5 See quote by Philips about the capacitor further down the page, what do you think?.......................................JR Link to comment Share on other sites More sharing options...
Nick Trollope Posted July 1, 2009 Share Posted July 1, 2009 Still comes down to the neon, I'm afraid. I'm having this conversation with John on TF, too....Dave, a 2-way circuit isn't that different from a single circuit (in this respect at least) and specifically they won't cause this problem with a CFL. I must have installed 100's of CFLs on 2-way switch circuits. Unless there are neons in the switches. Link to comment Share on other sites More sharing options...
Chancer Posted July 1, 2009 Share Posted July 1, 2009 Yes I have come across it once before, the starting circuit in the compact flourescent ballast uses a capacitor, this is very slowly charged by the small current passing through the neon until it discharges to neutral via the pre-heat coil. Then the cycle repeats. Link to comment Share on other sites More sharing options...
JohnRoss Posted July 1, 2009 Author Share Posted July 1, 2009 I think Nick and JR's are right about the neon providing a charging path for some capacitor and the time constant of the neon and its series resistor plus any resistance in the CFL must determine the flash rate which in our case is once every 3 or 4 seconds........................JohnRoss PS Not sure of the circuit of a CFL but it must have diodes in it to charge a capacitor with d.c. to give this time constant and resulting critical trigger voltage. I would be interested in looking at the cicuit of one if anyone can give an URL PPS A note in the local paper saying that from today you cannot get ordinary bulbs of 100W or greater only CFL types from now on in France, big brother or what, thought the intention is good. Link to comment Share on other sites More sharing options...
Pierre ZFP Posted July 1, 2009 Share Posted July 1, 2009 My paper says that you can't buy bulbs of > 100W anymore so I took it to mean you can still get 100W.Or am I just being pedantic? Link to comment Share on other sites More sharing options...
Chancer Posted July 1, 2009 Share Posted July 1, 2009 I worked for a few months running the manufacture of CFL's but I cant even remember the ballast circuit details these days, I think there was a timed preheat circuit (the initial dim glow) before the neon arc was struck. Link to comment Share on other sites More sharing options...
JohnRoss Posted July 1, 2009 Author Share Posted July 1, 2009 Our paper, The Nouvelle République, says more than or equal to 100W now, more than 75W by the end of the year, 60W by June 2010, 40W by 31st August 2011 and 25W by 31st December 2012 and maybe we both are!.................JR Link to comment Share on other sites More sharing options...
JohnRoss Posted July 1, 2009 Author Share Posted July 1, 2009 Found this which gives a circuit diagram of a CFL if anyone is interested and disconnected neon and problem solved.............................JRhttp://www.en-genius.net/includes/files/col_081307.pdf Link to comment Share on other sites More sharing options...
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