On 07.02.13 19:04, Leonardo Marsaglia wrote: > The basic thing that I need is a Square wave generator, that outputs 2 > signals one at 180ยบ from the other, and with a duty cycle less than 50%. > This is to avoid complications with the switching transistors. I'm almost > sure that hal could do this, even read the signals to adjust the frequency.
If a frequency of twice the desired output rate is used to clock a JK flip-flop, the result is two antiphase 50% MS ratio clocks, from Q and Q' respectively. The "less than 50%" duty cycle that you refer to is called "dead time", and typically ensures that totem-pole connected power devices do not conduct at the same time, shorting out the power supply. While that can be added by simple diode/resistor networks when driving power MOSFETs, it is already included in many gate drive chips, such as the IR2111, which provides a deadtime of 650 ns, typical. (Others are adjustable, IIRC.) All that would be required then, is a 2x clock from LinuxCNC, or just a DC enable, if a gated oscillator were simply turned on and off by LinuxCNC. That would be much more robust than generating the antiphase clocks in software, where a software hiccup could lose the deadtime, destroying the power devices, or melting other gear. (Just my $0.02. :) It sounds like a very interesting project, and a lot of fun, but susceptible to the wrong things glowing red hot. Erik -- A good scare is worth more than good advice. (Proverb) ------------------------------------------------------------------------------ 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
