You have just contradicted yourself. No matter what the load any inductive load will produce a voltage spike with reverse polarity when power is removed. be it a simple power on, power off, or the off periods of a PWM drive. The diode provides a shortcircuit path for the destructive voltage.I have run test for my work place and shocked them with osciloscope graphs of -400v spikes running around the system because of lack of diodes
BTW, you may want to start writing some nasty letters to IC manufacturers, because they have been putting clamping diodes across the transistors for decades. Like these guys, for example:http://www.mitsubishielectric-mesh.com/products/pdf/m54530p_e.pdfOr these flipping idiots:http://pdf1.alldatasheet.com/datasheet-pdf/view/202145/TI/UN2003A.htmlStupid, manufacturers! Don't they know any better?!!!!!!!!Must be a bunch of stupid programmers. lol
Quote from: sparkylabs on Mar 25, 2013, 06:31 pmYou have just contradicted yourself. No matter what the load any inductive load will produce a voltage spike with reverse polarity when power is removed. be it a simple power on, power off, or the off periods of a PWM drive. The diode provides a shortcircuit path for the destructive voltage.I have run test for my work place and shocked them with osciloscope graphs of -400v spikes running around the system because of lack of diodesWho contradicted whom?
Sparky,I happen to be an electrical engineer for a major aerospace company. So I guess if you lack confidence in my education, perhaps you should avoid flying. Having a bad day, are we?Honestly... it doesn't make a flipping difference, really. Back EMF gets shunted to ground with the diode. It follows the path of least resistance and the diode provides that. That super scary 400 VOLTS!!!!!! you are so eager to show us has practically no current capacity to it at all to it. It is just absorped by ground within femtoseconds. I can one up you and show you 1000V!!!! by walking across a carpet!!! But very doubtful I will blow a BJT by touching it. Why? Because it has practically NO current to it at all, not even close to enough to breakdown the junction in a BJT. FETs on the other hand... and even that is actually more theory and suspicion than even actually proven. The danger is all in the voltage itself and the way semiconductors are formed. A high enough potential across the collector to emitter MAY be enough to breakdown the junctions and the transistor self-destructs. MUCH more likely with a FET than a BJT. In fact, do you have any idea how many thousands of everyday products that you use that do NOT even have a diode in the circuit? Yet they keep on clammering away, happily. Imagine that!It CAN damage a transistor, and it is good practice to have a diode whichever way you choose to install it. But it is not even close to being as dramatic as you are making it. If one were to run a 12V motor (especially just a fan) and not even put a diode in there, I doubt they would ever even have trouble.You go read a book, Sparky.
I'm out of popcorn, damn. Lefty
The testing I refered to where i got -400V was to work out why thermostats in the system where being broken when a certain relay turned off a certain fan (24V 15A), so much for little energy and that was not even using cmos stuff AND the spike was arcing across relay contacts before getting the the cheap automotive thermostat
Oh and to answer your question: The cookie monster eats it. That's what happens to it.
Are you sure ? remember you can: 1) ask the audience, 2) phone a friend, 3) go for 50/50