Posts Tagged H-Bridge
Quadrupeds Need a Whole Lot of Motor Controllers
Each leg has it’s own motor controller to manage the two motors in each leg, and another two motor controllers will manage the four motors in the core. The leg motor controllers are shaped specifically to fit within the frame on one side. The other side of the upper leg frame will hold another PCB with some sensors (I’m planning on e-field and/or pressure sensors in the robot’s feet and on the leg itself.)
Each joint requires angular feedback for the motor controller’s closed loop system. This is accomplished by using special potentiometers through which the joint shaft will pass. The potentiometer is wired as a simple voltage divider, andĀ as the angle of the shaft changes, the potentiometer will give a different voltage output. This voltage will in turn be read by the motor controller and turned into useful data. The special potentiometers used here were a bit of an obscure find, but luckily they are a stock item at Digikey.In order to ease the routing of all the connections on a 2 layer PCB, I decided to offload the large BDM header onto a separate board, which can be screwed onto the leg frame when I load the motor controller firmware. Several pogo pins thenĀ make the programming connections to the test points on the controller PCB. I decided to get creative with the shape, and it turned out pretty neat.
I’m toying with the idea of putting a customized boot loader in the 9s12 controller, and giving the main processor (the Gumstix) programming control over all motor drivers. This way, instead of individually updating firmware on the motor controllers as I continue development down the road, I can instead just load one hex file into the Gumstix’ file system, and it will automatically update the firmware on all six motor controllers.
I also recently ordered the batteries I will be using to power the robot, 4x 2000 mAh LiPo batteries. I will be running then in a 2-series 2-parallel configuration to get 4000 mAh at 7.2 volts to run the entire robot. I still need to design and build a board that will fit underneath the batteries in the core of the robot, which will be responsible for battery protection/charging as well as power and control signal distribution to the four legs.Still a lot of work to go, but it’s getting closer to walking…
Mini Sumo PCBs…
Posted by Roko in Mini Sumo v6, Robotics on April 28th, 2009
You’ll also notice on the silk screen that I have given this robot a more creative name than Mini Sumo Version 6. I now call it “1.21Gw,” pronounced, of course, much as Doc Brown pronounced it in the timeless classic (no pun intended) “Back to the Future”
Now to finish it up and write some basic code for the robot games this weekend.
H-Bridge Fundamentals
An introduction into basic H-Bridge theory and operation, this article covers the fundamentals you need to know to make a working H-Brigde with N and P Channel MOSFETs