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Stellaris® Stepper Motor RDK User’s Manual

November 4, 2009

23

Also on this page are several LED status indicators, a simple reset circuit, and on-board user 
interface. The speed/position potentiometer's value is read by the microcontroller's ADC. Because 
the ADC's input span is 0-3 V, a resistor (R14) is used to pad the potentiometer voltage.

The microcontroller's on-chip analog comparator provides an over-current trip function. Diodes D2 
and D3 gate the greater of the two motor coil currents into an R/C network which connects to the 
inverting comparator input. Inside the microcontroller, this level is compared to a programmable 
voltage reference. An interrupt will be generated in the event of an over-current condition allowing 
the software to quickly shut-down the power stage.

Output Power Stage (Schematic Page 3)

The power stages on schematic pages 3 and 4 are identical. One power stage is used for each of 
the two coils in the bipolar stepper motor. 

The power stage consists primarily of a MOSFET H-bridge and associated gate drivers. The 
H-bridge allows the microcontroller to control the magnitude and polarity of the current in the 
motor. Each H-bridge has three logic control signals. PH_x1 and PH_x2 control whether the 
high-side or low-side switch is on. A common active-low enable signal can force all switches off.

To turn on the high-side MOSFETs, the gate voltage must be driven higher than the source. This is 
achieved by using a gate driver and a flying-[or bootstrap] capacitor. Using Phase A1 as an 
example: When the low-side MOSFET (Q4) is ON, diode D7 is forward biased and capacitors C16 
and C18 charge to almost 15 V. In turn, this charge allows the high-side MOSFET (Q3) to be 
turned on by the high-side gate driver. As the high-side MOSFET turns on, its source voltage rises 
taking the negative terminal of the flying capacitor along with it. The capacitor is sized to maintain 
a high-side supply voltage of at least HV

DC

 + 12.5 V during the ON state. If the capacitor 

discharges below 11.3 V (typ), the SPM's under-voltage lock-out circuit activates to prevent the 
MOSFET from moving outside its safe operating area (SOA).

Two 100m

Ω

 resistive shunts provide 100 mV/A current sensing. The resultant voltage is fed into 

an operation amplifier and into the comparator circuit on Page 2.

Page 3 also shows a linear hall-effect sensor for positional feedback. This circuit is not presently 
populated.

Table 3-1. Current Monitoring Circuits

Microcontroller 

Comparator

Microcontroller ADC

Function

Software programmable 
current trip

Measurement of phase 
current amplitude

Amplifier Gain

n/a

11

Resolution

137.5 mV (1.375 A)

10 bits

Scale

100 mV/A – 0.15 V

1 bit = 2.67 mA

Trip Threshold (typ.)

Programmable 
reference

In software

Trip Speed (typ.)

<10 us

Software-dependent

Содержание Stellaris

Страница 1: ...RDK Stepper 03 Copyright 2007 2009 Texas Instruments User s Manual Stellaris Stepper Motor Reference Design Kit ...

Страница 2: ...e are registered trademarks of Texas Instruments ARM and Thumb are registered trademarks and Cortex is a trademark of ARM Limited Other names and brands may be claimed as the property of others Texas Instruments 108 Wild Basin Suite 350 Austin TX 78746 Main 1 512 279 8800 Fax 1 512 279 8879 http www luminarymicro com ...

Страница 3: ...on Window 18 Chapter 3 Hardware Description 21 Block Diagram 22 Functional Description 22 Microcontroller Schematic Pages 1 2 22 Output Power Stage Schematic Page 3 23 Control Interfaces Schematic Page 4 24 Software 24 Chopper Control 24 Parameter Reference 26 Serial Protocol 26 Appendix A Parameters 27 Parameter Descriptions 27 Motor Running Configuration 28 Target Position 28 Maximum Current 28 ...

Страница 4: ...4 November 4 2009 Appendix B Schematics 33 Appendix C PCB Component Locations 39 Appendix D Bill of Materials BOM 41 ...

Страница 5: ... 4 2009 5 List of Tables Table 1 1 RDK Motor Specifications 11 Table 2 1 Description of GUI Main Window Controls 16 Table 2 2 Description of Configuration Controls 19 Table 3 1 Current Monitoring Circuits 23 Table A 1 Parameter Configuration Summary 27 ...

Страница 6: ...6 November 4 2009 ...

Страница 7: ...ure 1 2 Stepper Speed Torque Curve 11 Figure 2 1 On board User Interface 13 Figure 2 2 Stepper Main GUI Window 15 Figure 2 3 Configuration Window 19 Figure 3 1 Stepper Motor Control RDK Layout 21 Figure 3 2 Block Diagram 22 Figure 3 3 Chopper Waveform Generation 25 Figure 3 4 Current Control Software Flow 25 ...

Страница 8: ...8 November 4 2009 ...

Страница 9: ...l board and PC over a USB cable Customize and integrate the hardware and software to suit an end application This User s Manual and the Software Reference Manual are two important references for completing your project Software can be programmed in the motor control board using either the RDK GUI software or using a JTAG debug interface available from leading development tools vendors Features The...

Страница 10: ...s from PM and non PM motor construction Figure 1 1 Stepper Motor The rotor on a hybrid stepper motor typically has 200 teeth made from a suitable magnetic material and surrounding one or more powerful embedded magnets As the stator phase is energized the opposing pole in the next rotor tooth is attracted resulting in a single step Note that the torque curve of stepper motors is far from linear see...

Страница 11: ...emperatures Current to the motor should be adjusted so that the motor case temperature never exceeds 100 C Chopper Control A stepper motor can be operated at its rated DC voltage but only low step rates are possible This is because the current builds comparatively slowly in the stator coil To overcome this chopper control uses a supply voltage much higher than the motor s rating This allows the co...

Страница 12: ... reference design meets the following specifications Electrical Supported motor type Bipolar stepper Motor current rated current per coil 3 Amps Motor voltage continuous coil voltage 1 80 Vdc Supply Voltage 9 80 Vdc Mechanical PCB size 4 6 x 2 8 x 0 75 117 mm x 71 mm x 19 mm No heat sink necessary ...

Страница 13: ...current to the motor windings at each step in a stepping sequence The Stepper RDK firmware can be controlled in two ways The simplest way is using the on board interface which allows the user control of the motor speed or position using controls available on the RDK board For more complex control a PC hosted graphical program is available which not only allows setting of speed and position but als...

Страница 14: ...ped To start the motor running press the user button The motor begins running in the forward direction Forward is designated as clockwise Use the user button to start and stop the motor Each time the button is pressed the motor either starts running if it is stopped or stops if it is already running Each time the motor starts running it runs in the opposite direction from the previous time The pot...

Страница 15: ... is disabled and the knob and button have no effect If the program has not been used before then a dialog box appears that lets the user select the COM port to use Once a COM port is selected the program remembers the selection and does not ask again However at any time the user can re open the COM port dialog box by double clicking on the COM port indicator on the main panel The stepper motor ope...

Страница 16: ... Position Area Target Sets the position of the motor in steps The motor position can be set in two ways first by entering a value in the Target Position box or by clicking on the position slider and dragging it right or left to the desired position and then releasing it The position control is not available until the motor has been enabled using the Run button Actual Shows the position of the moto...

Страница 17: ...able if PWM mode is used and the current indicator will be grayed out Processor Usage Indicates the microcontroller CPU load by percentage Useful for estimating the loading of different applications and motor control algorithms Temperature Indicates the internal temperature sensor of the microcontroller 8 Special Indicator Area COM Port Displays the COM port number and status If the indicator is s...

Страница 18: ...are only be loaded if the motor is stopped Save Parameters to File The adjustable motor parameters can be saved to a file Selecting this menu choice causes all of the parameters to be read from the RDK board and stored to a file The parameters can only be stored to a file if the motor is not running Update Firmware This menu choice can be used to load new firmware onto the RDK target board A file ...

Страница 19: ...the winding current In PWM mode the Fixed Rise Time parameter can also be used see Fixed Rise Time Chopper In Chopper control mode the microcontroller firmware monitors the current flowing in the winding and switches the voltage to the winding on and off in order to keep the current at the desired value Closed loop PWM In Closed loop PWM control mode the firmware sets the PWM duty cycle based on t...

Страница 20: ...ast Decay mode during the time that no voltage is applied to the winding all the switches are open The current can no longer circulate and decays quickly 3 Step Mode Full With full stepping voltage is always applied to both windings and a four step stepping sequence is used Half With half stepping the voltage is off during part of the stepping sequence and an eight half step stepping sequence is u...

Страница 21: ...ponents complete the design by providing protection signal acquisition and power supply functions The entire circuit is built on a simple two layer printed circuit board see Figure 3 1 All design files are provided in the RDK CD Figure 3 1 Stepper Motor Control RDK Layout USB Interface Gate Drivers Mode Switch Speed Pot DC Bus Capacitors Fuse DC Power In Output to Motor Stellaris Microcontroller F...

Страница 22: ...or motor control including 6 high speed ADC channels a motor control PWM block and an analog comparator The RDK has a 20 pin ARM JTAG port for programming and debugging A standard debug interface can be connected to this header J1 Unallocated GPIO signals from the microcontroller are routed to pads labeled P1 P19 Several peripheral blocks are available for external use including SPI and UART1 The ...

Страница 23: ...ive low enable signal can force all switches off To turn on the high side MOSFETs the gate voltage must be driven higher than the source This is achieved by using a gate driver and a flying or bootstrap capacitor Using Phase A1 as an example When the low side MOSFET Q4 is ON diode D7 is forward biased and capacitors C16 and C18 charge to almost 15 V In turn this charge allows the high side MOSFET ...

Страница 24: ...n can be found in the Software Reference Manual and could be used as a general purpose control method from other hosts Software The Stepper Motor Control RDK software manages four primary functions Motor current control Real time chopper control of motor current Motor step sequencing Controlling the stepper motor s commutation sequence Motor velocity and position control Calculates motor speed as ...

Страница 25: ...l Figure 3 4 Current Control Software Flow Control Signal to Gate Driver Motor Winding Current Amps High side MOSFET ON Low side MOSFET ON Blanking Time Blanking Time Current Threshold ADC Sampling Start of step Chopping continues to end of step Read ADC Sample Sample Current Threshold ADC Interrupt ISR Start new acquisition Exit ISR Start OFF blanking timer Turn control pin OFF Y N Turn control p...

Страница 26: ...e current set point As an example the RDK GUI has several parameters that change chopper control behavior for motors and loads that have differing characteristics Parameter Reference See Appendix A Parameters on page 27 for a detailed description of the RDK s parameters Serial Protocol See the Stepper Motor Control RDK Software Reference Manual for more information ...

Страница 27: ...et Speed PARAM_TARGET_SPEED steps sec 10 10000 200 page 28 Acceleration PARAM_ACCEL steps sec2 100 60000 30000 page 28 Deceleration PARAM_DECEL steps sec2 100 60000 60000 page 29 Motor Drive Configuration Parameters Winding Resistance PARAM_RESISTANCE mΩ 100 5000 750 page 29 PWM Frequency PARAM_PWM_FREQUENCY Hz 16000 32000 20000 page 29 Fixed Rise Time PARAM_FIXED_ON_TIME μS 1 10000 800 page 29 Dr...

Страница 28: ...ar the target position at which time it decelerates to a stop This value is in whole steps so if Half Stepping mode is used then the actual stepping rate applied to the motor will be twice this value It may be difficult to get the stepper motor up to maximum speed if it does not have a load Acceleration This parameter is the rate at which the motor accelerates to reach the target speed Larger valu...

Страница 29: ...meter determines the PWM period Fixed Rise Time If PWM mode is used this parameter sets the amount of time at the beginning of a step that the winding is left with full voltage applied before PWM is used to control the current By leaving the full voltage applied to the winding the current rises as fast as possible allowing it to reach the drive current faster Caution If making adjustments to this ...

Страница 30: ...parameter specifies Chopper mode or PWM mode Chopper mode monitors the winding current while the winding is on When the current reaches the target value Drive Current it switches the winding off The winding remains off for the Off Blanking Time At the end of the blanking time the winding is turned on again and the current monitoring resumes In Open loop PWM mode the duty cycle is calculated to set...

Страница 31: ...ositive or 0 at each point in an eight half step stepping sequence In Micro Step mode the current in each winding is varied sinusoidally over a sequence of 8 microsteps per step In Wave Step mode full steps are made as in Full Step mode except that only one winding is energized at a time The unloaded motor runs smoother at slower speeds using half stepping but full stepping may be appropriate for ...

Страница 32: ...32 November 4 2009 ...

Страница 33: ...ics This section contains the schematics for the LM3S1968 Evaluation Board Contents Page on page 34 Microcontroller on page 35 Driver Coil A on page 36 Driver Coil B on page 37 Power Supplies and USB on page 38 A P P E N D I X B ...

Страница 34: ...ion 0 Jan 17 07 First Full Release History U_Stepper Microcontroller Stepper Microcontroller SchDoc U_Stepper Ph A Drive Stepper Ph A Drive SchDoc U_Stepper Ph B Drive Stepper Ph B Drive SchDoc U_Stepper Power Supplies Stepper Power Supplies SchDoc 0 1 Feb 07 07 Change USB device to bus power A Feb 09 07 First Production Revision A 1 Jul 10 07 Change C18 C19 C31 C32 to no populate Contents Page ...

Страница 35: ...LT TP7 ISENSEAB ISENSEA ISENSEB R2 1 0K R3 261K 0 01UF C4 ISENSEAB P10 P11 P12 P14 P15 P3 P16 P13 P1 P4 P5 P6 GND P2 GND R4 10K R5 10K 3 3V 3 3V Connect Optional Limit Switches to P1 2 and P3 4 Speed Position Control Pot 3 3V PA0 U0Rx 17 PA1 U0Tx 18 PA2 SSIClk 19 PA3 SSIFss 20 PA4 SSIRx 21 PA5 SSITx 22 PC0 TCK SWCLK 40 PC1 TMS SWDIO 39 PC2 TDI 38 PC3 TDO SWO 37 PC4 CCP5 14 PC5 CCP1 13 PC6 CCP3 12 ...

Страница 36: ...DT SDn 3 LO 5 VB 8 VDD 4 GND 2 U2 FAN73832 R21 33 0 1UF C16 PH_A2 15V 25V OMIT 10uF C19 100PF C12 0 1UF C15 R18 10K R20 20K R25 100 R26 100 VS 6 HO 7 IN 1 DT SDn 3 LO 5 VB 8 VDD 4 GND 2 U3 FAN73832 R22 33 0 1UF C17 25V 10uF C13 0 1UF C20 M1 MOTOR NEMA23 OUTLINE Stepper Motor Connections ISENSEA Q1 8 Can subst FDMS3682 for lower Rds on 4 5 6 7 8 9 1 2 3 Q3 FDMS3672 4 5 6 7 8 9 1 2 3 Q4 FDMS3672 4 5...

Страница 37: ... R43 1K R46 100K R45 10K R44 OMIT VS 6 HO 7 IN 1 DT SDn 3 LO 5 VB 8 VDD 4 GND 2 U6 FAN73832 R36 33 0 1UF C29 PH_B2 15V 25V OMIT 10uF C32 100PF C25 0 1UF C28 R33 10K R35 20K R40 100 R41 100 VS 6 HO 7 IN 1 DT SDn 3 LO 5 VB 8 VDD 4 GND 2 U7 FAN73832 R37 33 0 1UF C30 25V 10uF C26 ISENSEB 4 5 6 7 8 9 1 2 3 Q9 FDMS3672 4 5 6 7 8 9 1 2 3 Q11 FDMS3672 4 5 6 7 8 9 1 2 3 Q10 FDMS3672 4 5 6 7 8 9 1 2 3 Q12 F...

Страница 38: ...41 150UF TXD 1 DTRn 2 RTSn 3 VCCIO 4 RXD 5 RIn 6 GND 7 NC 8 DSRn 9 DCDn 10 CTSn 11 CBUS4 12 CBUS2 13 CBUS3 14 USBDP 15 USBDM 16 3V3OUT 17 GND 18 RESETn 19 VCC 20 GND 21 CBUS1 22 CBUS0 23 NC 24 AGND 25 TEST 26 OSCI 27 OSCO 28 U9 FT232RL USB Virtual COM Port R48 10K R47 4 7K 25V 10uF C48 VCP_RX VCP_TX 15V F1 4A 10 80VDC R49 261K R50 10K VSENSE 100V C42 150UF FB1 OMIT 25V 10uF C46 PJ 002BH SMT 1 2 3 ...

Страница 39: ...November 4 2009 39 PCB Component Locations This section shows the PCB component locations for the Stepper Motor RDK A P P E N D I X C ...

Страница 40: ...Power Supplies and USB ...

Страница 41: ...November 4 2009 41 Bill of Materials BOM This section provides the BOM for the Stepper Motor RDK A P P E N D I X D ...

Страница 42: ...use 13 FB2 FB3 2 BLM21PG221SN1D Inductor Chip Ferrite 2A 0805 220 Ohm 100MHz Murata 14 J1 1 N2520 6V0C RB WE Header Low profile Shrouded 2x10way SMT 3M 15 J2 1 43045 0409 Connector MicroFit 3mm 4pos header R A SMT Molex 16 J3 1 PJ 002AH SMT Connector 2 1mm DC power socket SMT CUI 17 J4 1 54819 0572 Connector USB Mini B SMT 5pin Molex 18 L1 1 DR127 331 R Inductor 330uH Power SMT Coiltronics 19 L2 1...

Страница 43: ...Gate Driver SO 8 Fairchild 42 U4 0 A1301KLHLT T IC Linear Hall Effect sensor SOT 23 OMIT Allegro 43 U5 U8 2 FAN4174IS5X_NL IC Low Power Rail to Rail Output 3MHz Op Amp SOT 23 Fairchild 44 U9 1 FT232RL USB UART Asynchronous Serial Data Transfer Chip SSOP28 Pb free FTDI 45 Y1 1 FOXSDLF 060 20 Crystal 6 00MHz HC49US SMT Fox 46 PCB 1 SRDK A PCB FR 4 4 52 x 2 80 2 layer Gloss black solder mask Imaginee...

Страница 44: ...44 November 4 2009 ...

Страница 45: ...ice TI is not responsible or liable for any such statements TI products are not authorized for use in safety critical applications such as life support where a failure of the TI product would reasonably be expected to cause severe personal injury or death unless officers of the parties have executed an agreement specifically governing such use Buyers represent that they have all necessary expertis...

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