On Sat, 2010-07-31 at 23:15 -0500, Jon Elson wrote: > I know a number of people are using my PWM servo amps with Mesa > controller boards. > A feature of the dumb control logic on the servo amp is that it needs a > short pulse in each direction > to clear the shutdown latches on the FET driver chips. I built a little > state machine into the driver to accomplish this, it is called the > "bootstrap" parameter. It gives 5% duty cycle pulses in each direction > on consecutive servo cycles, then goes to normal operation as commanded > by the PWM input. If you don't do this, the drive can act like it is > disabled until you attempt to move it both directions, then it will > suddenly come "live". > > So, has anyone written up a couple lines of HAL to do this, or how else > do you solve the problem? > > (This applies only to the brush version of the servo amp, the brushless > amp has a CPLD that manages this function.) > > Thanks, > > Jon
Is this the high side bootstrap that creates the high side FET gate control voltage? This has always seemed to create more trouble than it is worth. Why not have another supply with the proper voltage and not have to deal with the bootstrap? Or use N and P FET's? I know the bootstrap method may save a portion of the parts cost, but for the product quantities for the CNC market, it doesn't seem worth it. I may be showing my ignorance here. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ The Palm PDK Hot Apps Program offers developers who use the Plug-In Development Kit to bring their C/C++ apps to Palm for a share of $1 Million in cash or HP Products. Visit us here for more details: http://p.sf.net/sfu/dev2dev-palm _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
