Stepper Motor Driver

Stepper motor driver

Bipolar stepper motor driver board: this circuit board is used for driving a single small power stepper motor. The driver boardcan be connected to a stepper motor with a 3-5V power supply to a maximum of 2.5A current.

The Diode Inc. ZXMHC3F381N8 H-bridge MOSFET transistors are used in the circuit to drive the stepper motor windings, it isa complementary array containing 4 transistors to form an H-bridge. The advantage of using MOSFET is that this device issimpler to interface with the logic circuit. Unlike the bi-polar transistor, it is controlled by a gate voltage and the gate power isonly drawn at the transistion time. It consumes almost no gate power to maintain the device at the ON state, thus the heatdissipation on the device will be less. But the MOSFET requires a stronger pull up and pull down power to turn the channelsON and OFF. The interfacing logic devices to the gate terminals should use 74HCT, 74HC, and etc. series devices. Since thisMOSFET's gate threadhold voltage is 3V, the LVTTL (3.3V logic) should not be used to drive the transistors.

In the 2-coil, bi-polar stepper motor, the driving pulsesrequire 4-phase signals. The A terminal is alwaysinverted to A' terminal, same as the B-B' terminals. The

B-B' pulse phases are 90o lagging when it turns in a

clockwise direction and 90o

leading at a counter-clockwise direction.

stepper motor driver http://www.hteck.ca/electronics/stepper-motor-drv/sm-driver.html

1 de 3 16/03/2014 02:16 p.m.

The driver schematic contains 2 major input signals from the controller. The direction control (DIR) commands the rotor in turning clockwise orcounter-clockwise. The step pulse control (/STEP, inverted logic) turns the stepper motor one step ahead. The driver board circuit U2, 74LS93 ,a binary counter, a 74LS74 D-FF, U3, and a 74HCT157 2-1 multiplexor decodes the DIR and STEP signals and generates the sequence of4-phase stepping pulses.

Some controllers provide a signal to control the motor ON/OFF, the /EN is lower active input signal (0=ON). The /EN input needs to beconnected to GROUND when it is not used.

Testing on a Hewlett-Packard (HP) ScanJet stepper motor, which is a 5V supply bipolar stepper motor,there is not much information that can be found about the specifications for this motor. The only markingson the label is the part number: STH-39D1126, and that it has a 4.1 ohm coil resistance and 1.8degree/step.

The motor's wiring terminals connect to the driver board:A - YELLOWA' - REDB - BROWNB' - ORANGE

Testing the driver board in LinuxCNC 2.5

The Driver boards are being tested in LinuxCNC with 3-axis exampleG-code. Three HP LaserJet III printers' stepper motors are connected tothe driver boards which are driven by the lp0 (LPT1). The HP LaserJetIII printer stepper motor is 5.1V rated unipolar stepper motors. Thismotor can be wired in a bipolar mode with the winding's center tapterminals not being used, and the rated supply voltage is 7 volts.However, in the test, it is operating in a bipolar mode and the powersupply of 5V is used.

The HP LaserJet III stepper motor's wiring terminals connect to thedriver board in bipolar configuration;

A - GREENA' - WHITE / GREENB - REDB' - WHITE / RED

The BLACK and WHITE terminals are no connections.

Since there is the same waveform to drive the bipolar stepper motors and the unipolar stepper motors in full step mode. The same circuit can be


2 de 3 16/03/2014 02:16 p.m.

modified to drive the unipolar stepper motors by replacing the H-bridge MOSFET. The modified circuit is relatively simpler since it only needsfour N-channel MOSFET transistors The connections to the logic has a slight difference. Although the circuit does not support wave driving andhalf-step driving modes, the full step driving has the maximum torque size efficency and gives less vibration. This unipolar driver can operate athigher voltage supply, it supports up to 12V 3A motors.

The driver board is modified by replacing the two H-bridge MOSFETs withfour N-MOSFETs. The HP LaserJet III stepper motor is wired in unipolarmode. The BLACK and WHITE terminals are connecting to the +5Vpower supply.

Bipolar stepper motor driver schematicDownload (PDF file)

Unipolar stepper motor driver schematicDownload (PDF file)

Back


3 de 3 16/03/2014 02:16 p.m.

Documents

Stepper Motor Driver