On Mon, 2012-02-06 at 07:32 -0500, Erik Friesen wrote: > I am doing a bit of 3 axis cnc routing on pvc. I would like to set it and > forget it while it runs. I have been thinking about building, or buying if > available, something down this line. > > Parallel breakout for stepper drive. > > Microchip pic32 or similar to monitor incoming steps > > Encoders on steppers to compare against steps. > > Pic set up as usb HID device, with misc IO for jogging, etc. > > Amperage monitoring on 110 out relays, controlled with HID or aux parport > io. > > I would set up the amperage and stepper monitors on the control board to > flip a bit if things get out of whack, which would be netted to the > machine-on.
If you are using the parallel port to generate step/dir signals, just adding another parallel port, set up as input, should be able to handle encoders just fine. Currently, the only practical real-time interfaces are the parallel port and PCI, so in my opinion, encoder data should go through one of them. Off-loading the encoder counting function to a microprocessor is reinventing the wheel since Linuxcnc already has this and more built in. I think the tricky bit is in getting analog data into Linuxcnc. Analog is not so hard because a fast hardware FPGA signal generator can produce an analog like signal with PWM or PDM. For analog to digital remotes, I tend to think that PCI or the parallel port should be used with a Modbus or SPI converter. There are SPI sensors available: http://www.wallacecompany.com/machine_shop/EMC2/serial_adc/ http://www.wallacecompany.com/machine_shop/EMC2/serial_dac/ Modbus is becoming more mature for controlling VFD's with LinuxCNC: http://wiki.linuxcnc.org/cgi-bin/wiki.pl?VFD_Modbus Arduino's, PIC's and AVR's could be used to support remote sensors: http://axis.unpy.net/01198594294 http://wiki.linuxcnc.org/cgi-bin/wiki.pl?AVR (see bottom for Modbus) http://wiki.linuxcnc.org/cgi-bin/wiki.pl?ModIO I've been working with using an AVR with the parallel port, which would have the advantage of being real-time, but would need to be fairly local to the LinuxCNC PC. I'm thinking of having the AVR convert to Modbus and/or SPI for the remote units. Some Mesa products have SPI capability: http://www.mesanet.com/pdf/parallel/5i25man.pdf It looks like the 5i25 might have everything you need, but there are so many ways to peel a banana. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
