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TI’s New Brushless DC Motor Kit
Today I am going to review a new brushless DC motor controller board from TI. I will give a brief overview of how I set this up as well as some tips for getting started.
The DRV8312 Digital Motor Controller kit contains everything you will need to use to develop your motor control solutions with TI’s InstaSPIN-BLDC solution, which is a topic for another blog.
The kit contains the following items:
- MDL-LM3S818CNCD controlCARD featuring a Stellaris® LM3S818 microcontroller
- DRV8312 DMC baseboard with slot for the controlCARD
- Brushless DC Motor, NEMA17
- 24V 2.5A DC Power Adapter, 110-240V AC input, USA power cable
- USB-miniB to USB-A plug cable (for debug and serial communication)
- ½-inch blue jumper wires (for bridging power)
- Development Kit Application and Documentation CD
- TI’s Code Composer Studio™ IDE CD
Motor Control Card
TI designed the LM3S818CNCD to work with the DRV83xx baseboard series of development kits. The LM3S818 is preprogrammed with the necessary firmware to be controlled by the quick start GUI that is included on the Stellaris Development Kit CD.
The DRV8312 Baseboard that comes with this development kit has a number of interesting features. First, it comes with an ISO controlCARD socket (100-pin DIMM). This slot is for the LM3S818 control card connectors to provide optional +12vdc supply for logic and gate drive power. A connector for the +24vdc power supply is provided in the kit with an alternative DC power supply. The DRV8312 three-phase PWM motor driver chip. Each half-bridge has a low-side shunt current sense as well as a reset switch. There is a mode jumper, M1, for configuring cycle-by-cycle current limit or latched over-current mode. Connections are provided for a quadrature encoder and for hall sensor feedback.
Using the Kit – hardware setup
Okay, it’s out of the box. Now, remove the baseboard from the ESD static bag. You are wearing your static wrist strap that is connected to an earth ground, right? Next, if the motor control card is not in the control card socket of the baseboard, insert the LM3S818 card into the socket labeled “Control Card Socket.” The control card is keyed to match the control card socket—can’t mess this up.
ATTENTION: There should not be a jumper or two jumpers plugged into the edge of the LM3S818 control card opposite of the edge connector. The jumpers should still be in a small zipped locked bag in one of the small pockets of the development kit box. Leave them there for now, they are for using the control card in stand-alone mode.
The kit comes with a NEMA size 17 BLDC motor. I read the DK-LM3S-DRV8312 Readme First document from TI, which is for connecting the motor to the DRB8312 baseboard. Refer to this document if you are having any motor startup issues. Using a slotted screwdriver, screw in the three 20 gauge wires into the Motor connector with labels: MOA (black), MOB (red) and MOC (yellow), there are 5 other cables (26awg) that I didn’t need to use this time. There is a USB_A to USB_mini-B cable included in the kit, remove the cable from the box. The mini-B side will plug into the USB connector provided on the LM3S818 control card while the standard USB_A side plugs into the USB port of your laptop or desktop system. There is a +24 vdc 2.5A DC power adapter with USA power cable for 110-240V AC input, pull this out of the box and plug into the DC bus 24V power jack located near the motor connector on the baseboard.
Using the Kit – software setup
With the Stellaris Development Kit CD, I installed it directly to the C-drive and nowhere else.
I noticed three new unknown drivers after plugging in the LM3S818 card into my laptop. With the Dev kit CD/DVD still in the DVD drive, I updated each unknown driver from the Dev kit CD/DVD. The GUI for controlling the motor control card is located in the following folder – C:\StellarisWare\AppNotes\sw01289\GUI. The filename is “Sandstorm_InstaSpin-BLDC-GUI_v102.exe”, I placed a shortcut on the desktop for easy access.
After initially starting up the GUI, I noticed there were three indicators at the bottom of the main tab of the program. They should be green if the PC and LM3S818 are talking to each other. That was not the case for me. To connect to the motor controller card you may have to “connect” the PC to the LM3S818 card. Selecting “connect” at the top of the GUI, two options are available: “Start Connection Wizard” and “Connect”. For a first time run, I selected the “Start Connection Wizard,” then “Connect to Engine.” In the lower left corner of the connection wizard window under “Targets” box, I selected the [-]Texas Instruments/CortexM:Stellaris M3 device/Generic Stellaris M3 device.” Under the “Transports and Connection Methods” box, I selected “serial,” then the “select” button at the bottom right corner. This window should automatically close. If all is well, the three indicators at the bottom of the program will turn green. To connect to the motor, selected “Enable Motor” in the lower left corner of the GUI window.
Now, to make some motor noises!! At this point, the motor is ready to do your bidding. There are three graphs that will display Flux, Van and Vag. The software uses a “sensorless” algorithm to calculate these values, which is why we only had to connect three wires. The other unused wires are for the hall sensor feedback. To enable, select the image of a waveform with a yellow colored gate overlayed. This will start a “continuous read” that will graph all three items I listed. The settings tab will allow you to make changes to Startup Duty Cycle, Startup Current, Velocity Limit and a couple of other parameters to fine tune the motor control.
I found I could get from out of the box to controlling the motor in about 15 minutes, versus the hour or so reading all the documentation. However, that is probably why it only took 15 minutes to setup. The GUI that comes with the DRV8312 development kit can go a long way to helping the motor driver engineer get to their ideal motor control settings in a short period of time.
Nice development kit, relatively easy to setup and use.