On Sun, Oct 28, 2007 at 11:32:26AM +0100, Geert De Pecker wrote: > Chris, > > On your website, there is a picture of the mod you did to the sherline > spindle speed control. It looks like you bypass the max-speed trimpot > with an optocoupler. > > Are you able to get from lowest to full speed with this mod?
Yes. I had to set the pwm offset and scale very carefully. The response is pretty linear but 1% pwm does not give you 1% of the max speed. > Is this a regular optocoupler? Yes. > I understand you drive the coupler directly with the pwm signal without > any rc filter or so. Doesn't this make the speed less stable? I was > thinking about a solution like this, but would have put a rc filter to > 'convert' the pwn to a semi dc voltage. On that lathe, I have very fast PWM from the pluto-servo interface. If you want to use software PWM (actually I think you should use PDM) you may have to filter the output side of the opto or something. I'm not sure. If you want something a little fancier KB makes an isolator board with analog input. It can be set to 0-5V which is a great match for parport pdm. It has about the right RC filtering built in. (I used this on the NIST lathe). Chris ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
