On 03/28/2015 12:37 PM, [email protected] wrote: > I have a question about the voltage to drive a stepper motor > 12 volts works but higher voltages make the motor weaker > I am building a simple stepper driver > A nema 23 2.7 amp stepper motor and 36 volt power supply > The controls are hand held, forward ,reverse, stop, and speed > I built the controls and driver using a 12 volt battery to test > Now I completed the project and am using the 36 volt supply > The motor runs at the same speed but it is so weak I can hold the shaft and > stall the motor > This is also the same with 36 and 24 volt batteries > With a 12 volt battery I can not stall the motor > I am using http://piclist.com/techref/io/stepper/SLAm/SLAm_bld.htm and an > Arduino > I would be happy if someone would point out my stupidity > > Richard
These come to mind, and may have been mentioned by other replies. The schematic shows a 5 Volt logic power supply. I would check to make sure a full 5 Volts is provided at all times and that the 5 Volt supply and your signal source share the same ground. Do you have a BOB (break out board) on a parallel port or some other signal source. Are the signals buffered or isolated? The driver schematic shows 3.3k pull up resistors which will source 1.5 mA, which would allow using parallel port pins directly (usually have a limit of 3 mA, often more), but might not be especially fast. If the BOB has isolation with opto-isolators, common optos can be quite slow. Insure that the reference voltage (.29V) is at the proper level. The reference is used for half power and shutdown features which could keep the motor from using full power if there is a fault somewhere. I didn't see a callout for current limit resistors for 3 amps, I assume the callout would be .1 Ohms. Oops, the text does talk about setting which resistors to use. You can try to verify your setup by measuring the resistance between the senseA pin and Ground, and senseB pin and Ground. This should be .1 Ohm, but most meters will have a hard time measuring this. Test by touching the meter leads together first and note the reading. Then test the pin and ground and the difference between the two values should be .1 Ohm. If you are using software stepping signals from the parallel port, your PC will need good latency. Even with good latency, the signals will not be very fast. I usually limit stepping modes to 1/4 or 1/8 stepping. The motor impedance is important too. Generally, more current produces more torque, more voltage provides higher speed. If one turns the motor shaft, the motor will produce a voltage and act like a generator. The voltage produced is dependent on the motor speed. Conversely, if one wants to drive the motor electrically, the corresponding voltage needs to be supplied for the desired speed. Of course the stepper motor speed is set by the stepping rate, but the voltage needs to be high enough to support the desired speed. Motors have different voltage per RPM specifications. The motor coil resistance or impedance is also related to V/RPM. Some less common motors will have a high V/RPM and not be suitable with this driver and application. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/ ------------------------------------------------------------------------------ Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
