The cnczone link tom posted is what I have been working on. The current schem/pictures are here http://www.electronicsam.com/images/KandT/servostart/schem/latestcurrentlimit/ use at your own risk :)
It might be overkill for your application but might give you some ideas. The input is PWM/PWM (sending pwm in one input is cw - sending pwm in the other input is ccw) (plus an enable). I have run this directly from the printer port but am using the pluto for faster encoder counting when using it to run closed loop (servo). It has been lightly tested up to 22a 180v. (the limit right now is the boot strap diodes are only rated for 200v). For my app that should be fine as 150-160v is where my servos max out. This thing has evolved slowly over the last few years. Started out as a simple opto-isolated h-bridge. Added current limit and enable. (this when thru a few iterations as I had some issues with current paths and current sensing) finally after fighting current sensing issues (mainly trying to filter out the mosfet turn on spike) I added a blanking circuit. (makes it so the current sense circuit doesn't read anything for aprox first 5us the mosfets turn on). The way it is setup - the circuit is really designed for 20khz or lower pwm. couple videos of the previous versions.. ;) http://www.youtube.com/watch?v=qY-FCN5ZXkg&feature=channel_page http://www.youtube.com/watch?v=i3zB1ZJv8cM&feature=channel_page picture of latest version (one I brought to Wichita.) http://www.electronicsam.com/images/KandT/servostart/schem/latestcurrentlimit/right.JPG people had fun turning the servo shaft and running it into current limit. (it was set to 5a at the time) sam Tom wrote: > Ian Wright <watchm...@...> writes: > > >> Hi, >> >> I'm looking for inspiration as to how I can use a 12 volt >> 6-8 Amp motor >> to drive my mini-mill spindle. I'm currently using an old >> mains voltage >> teleprinter motor which, although it does the job admirably, >> is as noisy >> as hell and I have to leave the room while it screeches >> away. I've now >> got this nice little 12 pole 12 volt motor which should do >> the job >> better and quieter but, while I am fitting it, I would like >> to get some >> automatic control over its speed. So, does anyone know of any >> schematics/circuits which I could build to allow me to hook >> the motor up >> to EMC2 and send it meaningful M3 / M4's? >> >> Ian >> -------------------- >> Ian W. Wright >> Sheffield UK >> > > > Hello Ian, > > Since you mention "schematics/circuits" I am assuming that you intend to > build > your own H bridge controller for the 12V spindle motor that you have. True? > If > so, you will need to decide on what control signal (0-10-vdc + dir, pwm + > dir) > you will use. If, for example, you decide to use 0-10vdc + dir then you will > need to decide how to output it (CNC4PC, Mesa 5i20, motenc, etc.) and how to > properly isolate it so that switching noise from the spindle > amplifier/H-bridge > & motor commutator does not interfere with the logic side of your controls. > > Once you have an isolated spindle control signal, then you can adapt any > number > of H bridge controllers to use that signal. The Unitrode UC1637 is an H > bridge > controller that can be configured to use a 0-10v control signal, and could be > used to control a homebrew H bridge consisting of P channel high side / N > channel low side mosfets. See the datasheet here: > http://www.iutenligne.net/ressources/etudes_realisations/Lequeu/kart/pdf/SLUA13 > 7.pdf > > Here is a link to an open source dc servo design discussion that might help. > http://www.cnczone.com/forums/showthread.php?t=25929 > > Good luck, > Tom > > > ------------------------------------------------------------------------------ > Register Now for Creativity and Technology (CaT), June 3rd, NYC. CaT > is a gathering of tech-side developers & brand creativity professionals. Meet > the minds behind Google Creative Lab, Visual Complexity, Processing, & > iPhoneDevCamp as they present alongside digital heavyweights like Barbarian > Group, R/GA, & Big Spaceship. http://p.sf.net/sfu/creativitycat-com > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.339 / Virus Database: 270.12.46/2145 - Release Date: 05/31/09 > 05:53:00 > > ------------------------------------------------------------------------------ Register Now for Creativity and Technology (CaT), June 3rd, NYC. CaT is a gathering of tech-side developers & brand creativity professionals. Meet the minds behind Google Creative Lab, Visual Complexity, Processing, & iPhoneDevCamp as they present alongside digital heavyweights like Barbarian Group, R/GA, & Big Spaceship. http://p.sf.net/sfu/creativitycat-com _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
