steve@maths.warwick.ac.uk (Steve Rumsby) (05/22/91)
[Blanket disclaimer: I'm not a qualified electrician, just an semi-competent amateur who's very out of practice... ] Light slowly dawns...I now know whats going on. It's been so long since I've looked at domestic lighting circuits that I'd forgotten exactly how they worked. In the UK, at least, here's how the light and switch are wired: Live -------------------------------------------- |_____ | \ switch _____| | O bulb | Neutral------------------------------------------ The switch is a single pole switch in the live feed to the bulb. The security devices which are designed as straight replacements for a normal light switch have to work in this set-up, and if they want to draw power from the mains then the only way to do that is to trickle current through the bulb filament, even when it is "off". THIS WON'T WORK WITH FLUORESCENT BULBS. The comments about inductive loads and high startup currents may be true, but in this case seem to be red herrings. It doesn't matter whether the security switch uses a SCR or a mechanical relay, if it can't leak current through the bulb, it can't get power. So, it looks like I want either a battery powered device, or one that will take a neutral return so it doesn't have to leak through the bulb. I guess the former is preferred, since the latter means I have to hack at my walls to replace the cable to the switch to give it a neutral conductor. The search goes on... Steve. -- UUCP: ...!ukc!warwick!steve Internet: steve@maths.warwick.ac.uk JANET: steve@uk.ac.warwick.maths PHONE: +44 203 524657
rasnow@bek-mc.caltech.edu (Brian Rasnow) (05/24/91)
Disclaimer: I'm a physicist. If you need a little leakage current, how about a parallel resistor with the fluorescent tube?? Brian Brian Rasnow, Caltech, Pasadena, CA 91125 rasnow@bek-mc.cns.caltech.edu rasnow@caltech.bitnet