On Mon, 6 Feb 2012, Erik Friesen wrote: > Date: Mon, 6 Feb 2012 12:23:00 -0500 > From: Erik Friesen <e...@aercon.net> > 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] Control board > > I don't care about an analog measurement, I want the system to pause or > park when amps are outside of a set range. How would you do the first > scenario?
Measuring spindle current can be rather tricky as you normally need an isolated current sensor (with high voltage isolation and very high common mode noise immunity since the current will usually be sensed at a point with 180-360V PWM) Hall effect sensors are a common way to do this. The other way is a floating current sense resistor (but this normally requires a isolated floating power supply) For a small spindle where 1V drop across a current sense resistor is acceptable, a simple current sense resistor with an AC OPTO-isolator may be enough since the 1V is enough to activate the OPTOS LED. This is very simple but will be fairly inaccurate (LED turn on voltage will vary with temperature) and quickly ends up with too much power dissipation: 1A = 1W but 5A = 25W Also depending on the spindle drive electronics, you may not need to measure/sense any current since the drive does this itself. Running a servo spindle drive in torque mode allows LinuxCNC to monitor the spindle load directly (its just the PIDs output) > > On Mon, Feb 6, 2012 at 12:14 PM, Jon Elson <el...@pico-systems.com> wrote: > >> Erik Friesen wrote: >>> I have been looking pretty close at the pico systems board, however, as >> of >>> yet I am not clear how to integrate spindle amps monitoring with it. I >>> also want to monitor vaccum for a holddown system. >>> >> You just want an overcurrent limit, or you want an analog measurement >> available to LinuxCNC? The first should be fairly easy, assuming you >> have some kind of current sensor. The second is not easy, I just didn't >> put in a provision for analog inputs. If low-resolution is good enough, >> you could hook up an 8-bit ADC chip to 8 digital inputs and use >> the weighted-sum HAL component to turn that back into a value. >> >> Jon >> >> >> ------------------------------------------------------------------------------ >> Try before you buy = See our experts in action! >> The most comprehensive online learning library for Microsoft developers >> is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, >> Metro Style Apps, more. Free future releases when you subscribe now! >> http://p.sf.net/sfu/learndevnow-dev2 >> _______________________________________________ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users >> > ------------------------------------------------------------------------------ > Try before you buy = See our experts in action! > The most comprehensive online learning library for Microsoft developers > is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, > Metro Style Apps, more. Free future releases when you subscribe now! > http://p.sf.net/sfu/learndevnow-dev2 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
