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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
yeah i know Hboy007 i wanted tiemes too do the simple things first, before we hit him with the complicated stuff later, so he could at least get something working soon for is grade.
or ami not getting youre meaning? he needs somthing halfway good enough for school, we can help him progress but it might take more than the time he has, to get it perfect.
also, i think his problems are mostly due to the "bu508 whatterver" it would be less difficult to drive an STmirco, IXYS,IR, Fairchild IGBT or mosfet, instead
Registered Member #1667
Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374
>> I (too) wanted tiemes to do the simple things first, before we hit him with the complicated stuff later, so he could at least get something working soon for his grade.
I know, that should be what we all want and what I had in mind before all the details took over. There are different solutions to his problems with the initial circuit, some require a complete redesign of the power stage, some only aim at improving what he has started by arguments on an in-depth level of understanding of bjt dynamic characteristics (oops..).
I feel so sorry for him and all the confusion that I'd like to send ihm one or two BU2508AFI to finish this!
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
I also ran into this problem. BUxO8's need several amps base drive to work properly, but don't forget the heatsink. I used 2N3055's for basic flyback drivers but they aren't very robust if you short the output.
in fact you are better off incorporating protection circuits such as crowbarring (limits the damage) rather than replacing transistors all the time.
If you are careful TVS's can be had from any old junked 'brick or ATX PC power supply but watch out for the vicious charged capacitors within, they bite!
i once built a power supply using two PIC 12C508's and ten photoflash transformers, worked well. maybe use a 555 and 4017 going to an optoisolator, can generate 10% waveforms very easily.
the advantage of this approach is that even if the 555 goes Tango Uniform the chances are it won't fry anything as the 4017 will settle in one of the no output states.
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Bu508d breaking down.
