Hi Bob, I just made a test with a 470 ohm resistor at the base of the transsistor, but when the first pulse starts the stepper motor stops at that point and never rotate. The algorithm sends a pulse ( to a1, b1, a2, b2 ) with the following sequence: a1 : 1000 b1 : 0010 a2 : 0001 b2 : 0100 after each pulse a delay of 10 mS to keep the signal and works well but without enough torque. Augusto ----- Original Message ----- From: "Bob Ammerman" To: Sent: Monday, July 14, 2003 8:47 PM Subject: Re: Stepper motor how to increase the torque > 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 > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body