On Wed, 15 May 2013, Gene Heskett wrote: > Date: Wed, 15 May 2013 11:40:09 -0400 > From: Gene Heskett <[email protected]> > Reply-To: "Enhanced Machine Controller (EMC)" > <[email protected]> > To: [email protected] > Subject: Re: [Emc-users] Superglue, or Loc-tite for that motors flywheel? > > On Wednesday 15 May 2013 11:24:49 John Kasunich did opine: > >> The current in that design is very dependent on transistor parameters >> such as beta and Vbe that will change from part to part and with >> temperature. Adding emitter resistor(s) stabilizes things. >> >> On Tue, May 14, 2013, at 10:39 PM, Przemek Klosowski wrote: >>> On Tue, May 14, 2013 at 3:08 PM, Gene Heskett <[email protected]> > wrote: >>>> So it looks like I need to design a 10 amp constant current load, >>>> switch mode of course. >>> >>> Perhaps something simpler? I have a sinking feeling that the >>> electronics wizards will soon hand me my head on the platter but I >>> think that the following circuit might work as a current load: it >>> sets up a lousy voltage reference and uses it to trickle enough >>> current into the base of a Darlington pair to drive the desired >>> current through the load. >>> --------------------------------------------------------------------- >>> --------- > > That PNG you sent has the sense R in the wrong leg of the transistor John, > it should be in the emitter leg. > > Anyway, I just stumbled over some 400 volt, 15 amp darlington's at Jameco & > I will build one bias circuit, feed two of those in parallel but with > separate emitter R's in the .2 ohm range, $15 and change for 5 pieces by > USPS first class. I looked at the heat sinks that had bugs on them, but > they were 30 amp 45 volt PNP Germanium's, of little or no use here. > > I figure 2 of them sharing a heat sink about 5.5x10 x 2" tall, ought to > handle that till the cows come home dripping. > > That heat sink also has a 6 pack of 1N3210 diodes on it, 15 amp 150 volt in > a DO5 case, should make a nice bridge so this works in reverse too. ;-) > > Many thanks for the ideas everybody. > > 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> > Colors may fade in time. > A pen in the hand of this president is far more > dangerous than 200 million guns in the hands of > law-abiding citizens. > > ------------------------------------------------------------------------------ > AlienVault Unified Security Management (USM) platform delivers complete > security visibility with the essential security capabilities. Easily and > efficiently configure, manage, and operate all of your security controls > from a single console and one unified framework. Download a free trial. > http://p.sf.net/sfu/alienvault_d2d > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users >
When using bipolar transistors as high power current sinks, make sure you are not violating their secondary breakdown specs (a lot easier to kill than you might think) Peter Wallace Mesa Electronics ------------------------------------------------------------------------------ AlienVault Unified Security Management (USM) platform delivers complete security visibility with the essential security capabilities. Easily and efficiently configure, manage, and operate all of your security controls from a single console and one unified framework. Download a free trial. http://p.sf.net/sfu/alienvault_d2d _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
