After re-examining this I think the part I missed was the use of the word 'inserting.' If the resistors are inserted only at stopping points and removed when moving, that makes more sense. Still seems awfully inefficient though. Eric On Fri, 27 Feb 2004 17:05:02 -0600 Eric Christensen wrote: > I don't understand how this would help. If I understand what you're saying, > you have this circuit: > > 19R Step Coil > 24V--------\/\/\/---+----UUUU----------- GND > | > V1 > > > With this setup, V1 will be 5 volts when 1A is flowing through the circuit. > This means that as far as the stepper is concerned, this is identical to the > original 5V, 1A setup. But now you are wasting 20 watts in a resistor. > > What did I miss? > > Eric > > > > On Fri, 27 Feb 2004 23:56:45 +0100 > Robert Soubie wrote: > > > 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 -- 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