On Tuesday 21 May 2013 10:26:05 Peter C. Wallace did opine: > 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
Despite my confidence that I knew what I was doing, it turns out that the SOA ratings on the bugs I bought and which arrived while I was trying to get some sleep on a dairy farm in NYS, turns out to suck dead toads through soda straws, Peter. It appears that the only way I can make a 10 amp sink, would be to make >15 identical circuits and stack them. I'm not all that fond of semi's in series. Page 5 of this link <http://www.st.com/web/en/resource/technical/document/datasheet/CD00000005.pdf> defines the bad news. Operation in parallel, so they get the full jolt from the motor, says I'd have to use an emitter R high enough to keep the individual bug under .350 ma. So a 10 amp sink would need 30 of them. Sooo, I am back to wondering how much pure R I can find around the place that is not already in my EDM lashup. That has a pair of 50 ohm 200 watters, and those, even in parallel, won't do much more than slow it at about half the rate it was accelerated at by the controller. 10 ohms would be a more serious load. Using the 5 ohm I have from full speed, it could exceed 20 amps at the initial contact close an I can see demagnetizing the PM fields. Do you have any better ideas for a semi choice? These $2.25 each ignition coil switchers sure aren't it. Thanks Peter. 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> If you have to ask how much it is, you can't afford it. A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. ------------------------------------------------------------------------------ Try New Relic Now & We'll Send You this Cool Shirt New Relic is the only SaaS-based application performance monitoring service that delivers powerful full stack analytics. Optimize and monitor your browser, app, & servers with just a few lines of code. Try New Relic and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_may _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
