This is reminding me of the Linistepper http://www.piclist.com/io/stepper/linistep Plug, plug, plug... --- James. -----Original Message----- From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Robert Soubie Sent: 2004 Feb 27, Fri 02:57 To: PICLIST@MITVMA.MIT.EDU Subject: [EE ] Stepper motor voltage question On Fri, 27 Feb 2004 17:16:15 -0000, Alan B. Pearce wrote on Re: ] Stepper motor voltage question: Someone said: >>I run my mill on 24volts. Has plenty of torque, and have never had a >>problem with any of the motors. And you answered: >That would be a typical voltage to get the current to increase at >sufficient rate while stepping. However if leaving a motor stopped for >a while at this voltage you will find the motor will get very hot, >possibly damaging winding insulation. The way I have seen this sorted >is to use a switchmode regulator chip with a "change voltage" control >done by an external transistor changing the sense divider ratio. When >the control processor wants to move the motor it switches to high >voltage, waits a few milliseconds then starts stepping the motor. A few >milliseconds after finishing the motion the voltage is switched back to the holding voltage. Another solution is to limit the current by inserting resistors in series with the windings; this will provide low magnetizition times and good torque while limiting current when the motor has stopped. Computing the resistors values is easy; i e.g. the motor is 5 Volts @ 1 amp and it is fed from 24 Volts, then R = (24 - 5) / 1 or 19 Ohms; Dissipation is 19 Volts * Ampere or 20 Watts. Probably a good compromise could be to use a 15 Ohms 20 Watts resistor, part of the heath would go into the motor that can probably stand that (a rule of thumb is that you should be able to fry an egg on it). * Xrobert.soubie@free.frX (veuillez supprimer les "X") * http://www.astrosurf.com/soubie * Au royaume des aveugles, les borgnes sont mal vus... - P.Dac -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics