With a 4.7K base resistor you are getting at most about 1ma of base current. What do you expect the gain of your transistor to be? You could try about a 470 ohm to get 10x the base drive. Your transistors are probably not getting anywhere near saturation. Bob Ammerman RAm Systems ----- Original Message ----- From: "CVT-SSS" To: Sent: Monday, July 14, 2003 8:46 PM Subject: Re: Stepper motor how to increase the torque > Ok. Ishaan and Thomas, > > I also have tested the circuit using a TIP102 transistor, but the stepper > still rotate not continuously, at the left and right side turns slow and > very delayed, and after each delay goes back one or two steps .... what4s > wrong here ? maybe the resistors ( 4.7K ) connected from the pic to the base > of the transistor ? > > I also make some tests with an ULN2003 but I need to invert the signals to > low state to send the pulses. > > Augusto > > > ----- Original Message ----- > From: "Thomas C. Sefranek" > To: > Sent: Monday, July 14, 2003 7:08 PM > Subject: Re: Stepper motor how to increase the torque > > > > Your choice of driver transistors is poor. > > Use the TIP series or power FETs. > > > > * > > | __O Thomas C. Sefranek WA1RHP@ARRL.NET > > |_-\<,_ Amateur Radio Operator: WA1RHP > > (*)/ (*) Bicycle mobile on 145.41, 448.625 MHz > > > > http://hamradio.cmcorp.com/inventory/Inventory.html > > http://www.harvardrepeater.org > > > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body