Hall Effect Switches?
919244
If you are using the hall effect switch itself to change the magnetic field, I guess we would need to know what the amperage requirement of the electromagnet is to spec out the part.  \n\nThis answer is also difficult because we don't know the strength of the magnetic field used to trip the switch nor the time which the magnet would be in the switch range nor the distance from the magnet to the switch.\n\nIf you have access to a bunch of reed or hall effect switches, I would suggest trying several to see which one works?\n\nAlso -- a suggestion -- i would use the hall effect switch as a sensor switch only and not try to run it as a direct switch connected to an electromagnet.  Use it to trip a transistor or FET that will, in turn, drive the electromagnet.  \n\nDoes this help?
1161474
You can't. The polarity of a magnet is set. If you screw it up, sorry!
823421
light duty is the problem - would be very easy to make one using any push on connector in the circuit ( you need a spring loaded connector with the pin being non conductive - a 'blade' shaped pin would be the easiest to rig )\n\nanother possibility is to use a switch of any type ( a - b ) that shunts the circuit to a open   circuit  ( this can be activated by a pull - and switched back manually )
441296
In certain low volume and high speed circuits, transistors will always have their places. ALthough their are now many more radio chips.\nMIKE
171789
Many CRT's can do that. Take a look at these here:\n\nhttp://www.newegg.com/Product/ProductList.asp?Submit=ENE&N=2000190019+70002970+70000422&Subcategory=19&description=&srchInDesc=&minPrice=&maxPrice=&ATTR1=&ATTR2=&ATTR3=&ATTR4=&ATTR5=&ATTR6=2000190019+70002970&ATTR7=&ATTR8=2000190019+70000422&ATTR9=&ATTR10=
438682
sure. go to a science store or look up schematics on the web.
977381
Can you get your hands on a Flux Capacitor?
359816
http://www.vrml.k12.la.us/mike/Intech2/learning_about_magnets.htm\n\nCHECK IT OUT
873132
What sort of prints? What sort of current do you want to source? How few milliviolts do you want?
820585
If by C you mean "centronics" then YES there are A-B switches available, both manual and automatic that use the 1284 cable from PC to switch and 1284-centronics to the printers. (ALSO A-B-C-D!!)\n\nYou will just have to "shop around" on the various computer store sites.  Remember to use the shortest cables possible. Cables normally do NOT come with these switches, but are purchased locally.\n\nAn automatic switch will cost you about $30.00.  I use one myself, and it switches depending on which printer I pick from my list.\n\nThey can also be used in reverse to connect 2-4 computers to 1 printer.\n\nThe OTHER alternative is an PCI accessory card containing additional printer ports.  These are ALSO available, from the same sources and are USUALLY cheaper, but require an available slot on the MB.
1086026
You can get an idea on counting the discs on the insulator string and multiplying by 12kV/disc.\nAgain it is only a general rule of thumb and is not accurate.\n\nSource 50 years as an Electrical Engineer
898940
You can find printable schematics on the page I've linked below.\n\nGood luck.
170254
Try these sites. Some have better explanations than others.\n\nSwitching and inverters: http://www.kpsec.freeuk.com/trancirc.htm\nAmplifiers: http://www.tpub.com/neets/book7/25c.htm\nLogic gates: http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/trangate.html
195389
Rotational speed sensors have different types according to the operating prenciples of the design such as hall effect sensors, inductive sensors and magnetoresistive. The following link is about the hall-effect theory...\n\nhttp://w5ac.tamu.edu/~kc5nnw/359/wheelspeed/sensors.html\n\nThis is about a magnetoresistive type manufactured by philips:\nhttp://www.semiconductors.philips.com/acrobat_download/applicationnotes/KMI16-15.pdf#search='rotational%20speed%20sensors'\n\nhope I helped...
699448
There are mechanical ones, and electronic ones.\n1) Mechanical: A clutch, usually made of 2 magnets. One magnet rotates, the other one is fixed to a spring-loaded needle. The faster the first magnet rotates, the further the needle goes clockwise.\n2) Electronic: \na) Optical: The drive shaft has a marker in a colour distinctively different from the shaft's colour. A photo reflector (photo diode and photo transistor combination) reads the changes in colour (brightness), and produces pulses which can be electronically counted during fixed time periods.\nb) Hall Effect: Instead of colour markers and photo detection, a hall sensor is used at an irregular (metal) shape of the drive shaft. The rest is the same.
827050
Yupp... but unfortunately is a hardcopy on my desk. Perhaps you may straight to tell us what\n\n1. You are designing from HT to Transformer 11kV / 415V\n2. You are designinig from Transformer to LV ??\n3. What is the kVA of the transfomer?
858307
City and Guilds in electronic engineering, at a guess?\n\nOnly a guess mind - why dont you call the local company that installs them, or even ask your local fire brigade?\n\nHope that helps.