Tuesday, December 1, 2009
ALMOST DONE
Well, I'm busy with the dual pulse code for the processor and also a couple of bugs that is p***ing me off :)) I guess everyone is asking "why so many Mosfets?". Many Mosfets in parallel lowers the resistance that lowers the heat and increase the amps. The difference between six of these Mosfets and eighteen is a couple of hundred amps more and a welder that is not going to overheat and burn out. You can also see that I get excellent controlled welds at much lower energy rates than commercial welders out there. I'm also turning this Mosfets on and off at precise calculated speeds according to the data sheets to prevent them from going up in smoke.
I'm in the process of ordering more boards and will hopefully be done with the programming by the time they come in to make it available to you guys.
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Hi,
ReplyDeletedo you sell the pcb and construction manual ?
what is or would be the price ?
i have some batteries needing good welds asap :^)
kind regards,
Nice work Fritz! I've got batteries piling up, cant wait to have a real welder!
ReplyDeleteLookin good!
Shawn
so close I can almost taste it
ReplyDeleteha, I'm already walking around looking at stuff I could stick together with this. Good work, keep me in line for a few boards. :)
ReplyDeleteGreat progress Fritz! Nice to see a built board. How are the spot welds compared to your previous designs? Have you scoped the voltage across the fets themselves, to see if there is any inductive kickback generated during a spot weld? This tends to kill fets the quickest. I am well versed at surface mount soldering, with plenty of Metcal equipment, when ever the time comes to build boards. -Mike
ReplyDeleteMike, the spot welds are more precise and the on resistance of the mosfets on this welder are much lower than the SCR's on the previous one putting out a much higher current (1000+ amps).
ReplyDeleteWe are almost making a dead short and have no voltage spikes that will kill the mosfets. Mosfets are usually killed by too fast turn on/off speeds (Amps/uS), too high gate voltages, too much current, heat and very important Time(high currents longer than 8-10Ms).
I'm glad to hear that the welds are improved. The voltage spikes I think of, occur during a spot weld when there is a spark, after the fets have turned off. That spark is part of the over voltage spike generated noise that can hit a fet and damage it. Voltage can kill a fet without even warming it up. Another fet based welder had this exact problem. That's why I asked about it. Thanks for all of your great work Fritz.-Mike
ReplyDeleteMike, you must have read about the guy on endless sphere. If this is the guy you are talking about then I can tell you that he had other design problems that had nothing to do with a voltage spike. Go look at PodeCoet's welder on Youtube, he turns his mosfets on and off, producing a spark and cutting metal with it without killing his mosfets.
ReplyDeleteThat sounds like the guy Fritz. Are both rows of fets in parallel or does each row have it's own pulse?
ReplyDeleteI finally had the time to look up the video of that guy cutting metal with his setup. Most impressive. I'm not sure I'd need the capability to cut metal, but could your system do that if desired? Are both rows of fets in parallel or does each row have it's own pulse? -Mike
ReplyDeleteYes Mike, this welder can cut metal by just adding code to the microprocessor. I don't intend to do that though because this is a welder and not a cutter and yes all Mosfets are in Parallel.
ReplyDelete