hziemann@daisy.waterloo.edu (Hans Ziemann) (02/13/91)
I am new to this newsgroup, and have not had time to do any reading. I have a simple question that a few people may be able to help me with, if you are in the right geography. I am taking a power control course right now, and we got to discussing light switches. A few years ago, when I was in Germany, studying at the Technische Universitaet Braunschweig, I noticed that they have light switches that turn them selves off after a short time. These were used in hallways, garages, and the like. We have tried our darndest to try and propose a simple way of making this work, but have failed miserably. I would like to make one of these as a course project. Could someone in Germany or otherwise, who knows how these switches work, send me a description or even a schematic (I understand both the north american convention and the european convention -- just tell me which one it is). Or, if you know of someone who knows how this works, could you pass allong this request? Please send it to me directly, as I have trouble keeping up with newsgroups. If you too are interested in this, send me mail, and I will let you know once I find out. Please send it to me at hziemann@daisy.waterloo.edu hziemann@daisy.uwaterloo.ca or equivalent... I have canabalized dimmer switches already and think the process is somewhat similar. But, then again... Any and all help will be greatly appreciated. Thanks a bunch. Hans Ziemann University of Waterloo Electrical Engineering
hziemann@daisy.waterloo.edu (Hans Ziemann) (02/13/91)
I should add, that a bimetal bar is quite unlikely, in that the switch can be repeatedly activated in close succession, and there are no noticable shorted time periods. I agree that it is a simple solution, but based on thermodynamics and the observed behaviour, I do not think that a bimetal bar could cool that quickly. I hope that there is another solution. Hans
agn@bovic.Eng.Sun.COM (Andreas G. Nowatzyk) (02/13/91)
Said switches were usually based on a pneumatic monoflop in a remote wiring closet. The relay coil depresses an air-piston with a valve to let the air rush out and an adjustable leak that determines the time delay until the contacts open. It is retriggerable: the delay starts from the moment you release the momentary light switch. All switches are wired in parallel and are frequently illuminated with a neon light that draws a small current through the relay.
Norbert.Zacharias@arbi.informatik.uni-oldenburg.de (Norbert Zacharias) (02/13/91)
hziemann@daisy.waterloo.edu (Hans Ziemann) writes: >I noticed that they have light switches that turn >them selves off after a short time. Hi Hans It works very simply. U have some of paralell wired switches s1 to sn. With that u trigger the relay rel. This relay / is a special one. It opens after a elected *---------/ 0------* time. You can buy it in elektricstores | s1 | | / | ####### *---------/ 0------* # rel # | s2 *----------#######--------------| | / | # | *---------/ 0------* # | | s3 | / % % | | / | ----/ 0-----% L %------* *---------/ 0------* | % % | | sn | |--0 | | 220 V AC |---------------------------*--------------------------0 hope this help Norbert -- ============================================================================= Norbert Zacharias Norbert.Zacharias@arbi.informatik.uni-oldenburg.de FB Physik 148964@DOLUNI1.bitnet Carl-von-Ossietzky-Universitaet Tel. 0049-441-7983527 Was Du nicht willst das man Dir tu, das will auch nicht was willst denn Du? Heinz Erhard =============================================================================