On Sunday 10 February 2013 18:52:38 Leonardo Marsaglia did opine: Message additions Copyright Sunday 10 February 2013 by Gene Heskett
> Thank you guys for your recomendations. I've been trying and succeded > (more or less) using oscillators like the ones from the PC switching > power supplies, all of this based on DIY circuits found on the > internet. The thing is that, since I'm planning to use LCNC to move the > coil along the part, it would be pretty awesome if the system could > handle the heater control part too. > > Anyway, the real deal here is always how to have a clean square signal > to fire the igbt's. I'm using dedicated IC's to turn on and of the > transistors the one I used is TL494, but the matter is I always have > little spikes at the output of the firing IC's, not at the oscillator's > output. I couldn't attach a picture of the scope since is too big. > > Those spikes have a duration of about 1 uS, but I don't know if this is > secure and I don't want to blow up the igbt's. In the picture there's > only one of the signals, there's the other one 180؛ phased that has the > same problem. 1 microsecond can be an eternity to an IGBT. As for your spikes, make sure that the scope is /not/ grounded thru its power cordage, but is grounded locally to your circuit. Even a 6" ground lead can and often will show over voltage spikes where there really aren't any. > Again thanks a lot for your help, I decided to talk here about this > because I know there's a lot of people here with way too much knowledge > about power electronics, so If you can help me a little I would be very > thankful! > > Leonardo. > > 2013/2/8 Peter C. Wallace <p...@mesanet.com> > > > On Fri, 8 Feb 2013, andy pugh wrote: > > > Date: Fri, 8 Feb 2013 09:00:58 +0200 > > > From: andy pugh <bodge...@gmail.com> > > > Reply-To: "Enhanced Machine Controller (EMC)" > > > > > > <emc-users@lists.sourceforge.net> > > > > > > To: "Enhanced Machine Controller (EMC)" > > > <emc-users@lists.sourceforge.net > > > > > > Subject: Re: [Emc-users] Signal generator for induction heating > > > > > > On 8 February 2013 00:29, Sebastian Kuzminsky <s...@highlab.com> wrote: > > >> Maybe a stepgen component in quadrature mode? That would let you > > >> easily control the frequency of the output signal. > > > > > > That would be 90 degrees phase-shift I think, so not quite right. > > > > > > siggen might be the way to go. I think there are bridge control > > > chips that handle the dead-time in hardware, and that might be a > > > more reliable approach. > > > > > > I think that the three-phase PWMgen on Mesa cards has complementary > > > signals, with deadband, that might be worth putting an oscilloscope > > > on. > > > > > > -- > > > atp > > > If you can't fix it, you don't own it. > > > http://www.ifixit.com/Manifesto > > > > This sounds like an ideal application for an Arduino (or cheaper > > microprocessor) with an _isolated_ serial link to set the parameters. > > Many little Micros have PWM hardware that will generate > > non-overlapping push pull > > drive though it may be harder to find one that can adjust the > > frequency and duty cycle independently. > > 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> Parkinson's Law: Work expands to fill the time alloted it. I was taught to respect my elders, but its getting harder and harder to find any... ------------------------------------------------------------------------------ Free Next-Gen Firewall Hardware Offer Buy your Sophos next-gen firewall before the end March 2013 and get the hardware for free! Learn more. http://p.sf.net/sfu/sophos-d2d-feb _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
