L23_Stepper Motors

L23_Stepper Motors - Stepper Motors ECET 209 – Lecture 23...

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Unformatted text preview: Stepper Motors ECET 209 – Lecture 23 Introduction to Microcontrollers ECET 209 Purdue University 2 Stepper Motors • • • • • Move in small increments of rotation Can hold a position indefinitely under load Can rotate continuously Can move quickly to position and “freeze” Are used for – robots – printer head positioning – disk drive head positioning ECET 209 Purdue University 3 Stepper Motors • Permanent Magnet Rotor • Set of Windings – Create Poles – Orientation allows • A Slightly Shifting Magnetic Field • By Activating One Field at a Time • That Step Around the Motor ECET 209 Purdue University 4 Electrical Characteristics +V Coil 1 Coil 2 Coil 3 Coil 4 control 1 2 3 4 ECET 209 Purdue University 5 Stepper Operation Coil 1 Coil4 Coil2 Coil 3 ECET 209 Purdue University 6 Stepper Operation Coil 1 Coil4 Coil2 Coil 3 ECET 209 Purdue University 7 Stepper Operation Coil 1 Coil4 Coil2 Coil 3 ECET 209 Purdue University 8 Stepper Operation Coil 1 Coil4 Coil2 Coil 3 ECET 209 Purdue University 9 Stepper Operation Coil 1 Coil4 Coil2 Coil 3 ECET 209 Purdue University 10 Electrical Characteristics +V Coil 1 Coil 2 Coil 3 Coil 4 control 1 2 3 4 ECET 209 Purdue University 11 Stepper Modes • Full Step • Half Step • Wave Drive ECET 209 Purdue University 12 Full Step Sequence C o il 1 C o il 2 C o il 3 C o il 4 1 0 1 0 1 0 0 1 0 1 0 1 0 1 1 0 7.5 degrees / step ECET 209 48 steps / rev Purdue University 13 Half Step Sequence C o il C o il 2 C o il 3 C o il 4 1 0 1 0 1 0 0 0 1 0 0 1 0 0 0 1 0 1 0 1 0 1 0 0 0 1 1 0 0 0 1 0 3.75 degrees /step ECET 209 96 steps /rev Purdue University 14 Wave Drive Sequence C o il 1 C o il 2 C o il 3 C o il 4 1 0 0 0 0 0 0 1 0 1 0 0 0 0 1 0 7.5 Degrees per step, 48 steps/rev ECET 209 Purdue University 15 Micro generates sequence Micro Coil 1 Coil 2 Coil 3 Coil 4 Port ECET 209 Purdue University 16 Full Step Sequence C o il 1 C o il 2 C o il 3 C o il 4 1 0 1 0 1 0 0 1 0 1 0 1 0 1 1 0 7.5 degrees / step ECET 209 48 steps / rev Purdue University 17 Half Step Sequence C o il C o il 2 C o il 3 C o il 4 1 0 1 0 1 0 0 0 1 0 0 1 0 0 0 1 0 1 0 1 0 1 0 0 0 1 1 0 0 0 1 0 3.75 degrees /step ECET 209 96 steps /rev Purdue University 18 Micro generates sequence Micro Port ECET 209 Purdue University 19 Counter generates sequence Coil 1 Coil 2 Coil 3 Coil 4 UP/DN clock counter ECET 209 Purdue University 20 Position Sensor • • • • The motor’s gear has a slot cut in it This slot serves has a reference indicator The lab board has an IR gap sensor The output of gap sensor is provided in the IO header of the stepper board ECET 209 Purdue University 21 In Lab • Supply the PLD a Direction bit – CW = 1 – CCW = 0 • Supply a STEP pulse ( High then Low ) – Speed Limit of 250 steps / second • Delay between steps • Monitor the reference indicator – Determine when the motor is “home” ECET 209 Purdue University 22 ...
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