On Wed, 2010-12-08 at 13:53 -0500, John Kasunich wrote: > On 4 December 2010 00:46, Kirk Wallace <kwall...@wallacecompany.com> > wrote: > > > > I'm working on using an ATtiny to watch EMC2's charge pump. > > Why not use a charge pump circuit to watch the charge pump signal? > > That is what it was designed for, and is probably the most fail-safe > solution. The timeout period is set by the capacitors and resistors > you choose, and can't get accidentally changed or disabled. > > A charge pump circuit consists of two diodes, one small capacitor > (a few hundred pF or a few nF), one medium capacitor (a few tens > of nF), and a resistor. Also needed is something to look at its > output and turn off the dangerous stuff if the output drops too low. > That can be as simple as a transistor driving a relay coil, or you > could use a schmidt trigger input logic gate followed by whatever > you need to drive.
This is what I have from the last time I played with the above type of circuit (sourced by JK?): http://www.wallacecompany.com/machine_shop/Shizuoka/watchdog-1b.png It worked on my breadboard but didn't work when I transferred it to a PCB. Other things came up and I didn't get back to fixing it. > No microcontroller, no programming, no configuration, no bits. > Analog lives! > > John Kasunich The analog method is probably more practical, but the digital solution may be viable too. It may be possible to do this with very few components (Vregulator, cap or two, ATtiny2313), at the same cost and have more flexibility (wide charge pump frequency range, learning mode, different fault responses, complex WD signal). I'm still playing with it, and for me the programming hurdle is pretty high, so who knows what the result might be. For someone needing a one-off circuit for a particular machine, the analog circuit above is probably the quickest solution. Especially, if there were(was?) a widget or cloud app that one could use to calculate the part values and model performance (Spice? but that is another unfilled time sink). -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ This SF Dev2Dev email is sponsored by: WikiLeaks The End of the Free Internet http://p.sf.net/sfu/therealnews-com _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
