watt is an energy rate. energy is watt*second. a 120 V 500 W lamp should have a resistance of about 29 ohm at operating temperature but will have a much lower resistance when cold (10-20% of on resistance maybe?)
other things walmart has that could potentially dissipate energy: grapite pencil leads, coffee makers or hot plates or crock pots, a countertop cooking burner (~20 ohm when cold), auto battery tester maybe, something else that has a brushed motor in it like a drill with a paint mixing attachment in a bucket of heavy oil, carbon rods from alkaline batteries, a stainless steel container full of really salty water with a stainless steel utensil suspended in it, a hair dryer, a discharged lead-acid battery, a space heater, a 12 volt air compressor attached to a small tire. --- On Sat, 5/11/13, Gene Heskett <[email protected]> wrote: > From: Gene Heskett <[email protected]> > Subject: [Emc-users] Question on stopping a 1HP treadmill motor > To: "Enhanced Machine Controller (EMC)" <[email protected]> > Date: Saturday, May 11, 2013, 5:45 PM > Greetings all; > > As I install the motor on my mini-lathe, it occurs to me > that if I do a set > of ice cube relays driven by those toys on the C41 board, it > strikes me > that with that huge flywheel fan combo, even an e-stop will > coast several > revolutions of the spindle. > > When I did the PMDX-106 for the mill, I used 2 relays, one > to switch > between the output of the controller with its DPDT poles, > the back side of > which dropped a 10 ohm 20 watt resistor across the motor to > make use of its > generating ability as a means of stopping it fairly rapidly. > As in 2500 > revs to zero in just a hair over 1 second. The 2nd > relay was used in the > usual DPDT reversing circuit. > > There isn't that much inertia in that setup, but this will > have a cast iron > fan cum flywheel that weighs a good 2 pounds to stop. > So a 10 ohm 20 > watter, taking the dump from 7000 rpm, is likely to be > considerably hotter > than bright red internally by the time its down to 100 rpms > as that will > translate to about a kilowatt of stored energy. > > 20 ohms won't have to take quite as much of a rapid thermal > shock, but the > wattage will be similar, so I don't see any way to make it > work that > doesn't involve a panel of at least 8 similar resistors. > > Unless someone else has a better idea? How about I > find some sockets for > the 500 watt halogen lamp sticks & use 2 of them in > series? > > Basically anything I can make off the local walmart shelves > (for under 50 > bucks that is). > > Cheers, Gene > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! > My views > <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> > Kansas state law requires pedestrians crossing the highways > at night to > wear tail lights. > A pen in the hand of this president is far more > dangerous than 200 million guns in the hands of > law-abiding > citizens. > > ------------------------------------------------------------------------------ > Learn Graph Databases - Download FREE O'Reilly Book > "Graph Databases" is the definitive new guide to graph > databases and > their applications. This 200-page book is written by three > acclaimed > leaders in the field. The early access version is available > now. > Download your free book today! http://p.sf.net/sfu/neotech_d2d_may > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Learn Graph Databases - Download FREE O'Reilly Book "Graph Databases" is the definitive new guide to graph databases and their applications. This 200-page book is written by three acclaimed leaders in the field. The early access version is available now. Download your free book today! http://p.sf.net/sfu/neotech_d2d_may _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
