Pololu Blog (Page 4)
Welcome to the Pololu Blog, where we provide updates about what we and our customers are doing and thinking about. This blog used to be Pololu president Jan Malášek’s Engage Your Brain blog; you can view just those posts here.
This is the second post in a series about how to make a Balboa 32U4 robot balance. Last week I talked about selecting mechanical components. In this post I will cover the inertial sensors included on the Balboa’s control board and how to use them in your code.
The key to Balboa’s balancing ability is the built-in ST LSM6DS33 IMU chip, which combines a 3D gyroscope and a 3D accelerometer. The Balboa also includes an ST LIS3MDL 3-axis magnetometer. Both sensors are connected to the AVR via I²C, giving it access to a total of nine sensor channels. These nine channels can be used in software to make an AHRS (attitude and heading reference system), a system that gives the robot a sense of its orientation in three dimensions. AHRS software is particularly important in aviation/drone applications, but for basic balancing, you don’t need anything that complicated. In fact, a single gyro channel is enough to determine the robot’s angle of rotation relative to vertical. The gyroscope’s y-axis channel measures the Balboa’s forward/backward rate of rotation; that is the channel we will be looking at here. Continued…
If you’re following Paul’s blog series about getting your Balboa robot balancing, you’ll probably want something to protect it when it falls. When I was working with my Balboa, I got a set of prototype arms that our mechanical engineers have been developing, but I felt they were missing a little something. So instead, I took a Beefy Arm Starter Kit from Thingiverse and used OpenSCAD to add adjustable mounting hubs to the arms. I printed two sets of arms with our RigidBot 3D printer and mounted them to the side rails on the Balboa chassis using 25 mm M3 screws and M3 nuts. They’ve been great for keeping obstacles and the floor at arm’s length from my electronics while I drove the robot around with an RC transmitter or through a Raspberry Pi web interface (example code coming soon!).
You can find these beefy arms for the Balboa on Thingiverse if you want to try 3D printing your own. The OpenSCAD script is also available there in case you want to customize your arms.
Customer Elise Pham made a bionic hand: a two-fingered gripper triggered with biofeedback. A Pololu Maestro servo controller monitors the trigger source and signals the servo to close the gripper. In this video, she uses a mechanical sensor for biofeedback, and she is exploring using a MyoWare Muscle Sensor as a future enhancement. Her earlier video shows using a MyoWare Muscle Sensor to control a servo like in our demonstration video.
April 10 update: Elise’s project won 1st Award for the 2017 Synopsys Science Fair and was also nominated to advance and compete in the 2017 National Broadcom MASTERS. Additionally, Elise was selected by the Santa Clara County Office of Education to participate in Steve Wozniak’s Silicon Valley Comic Con Science Fair.
Customer Thomas Broughton made a line follower robot controlled by a Raspberry Pi that directly connects to a Pololu QTR-8RC reflectance sensor array. A Raspberry Pi is not typically good for a timing-sensitive application because it runs a regular computer operating system, so it’s nice to see Thomas was able to get it to reliably read the sensor array. The robot also uses four 42×19mm pololu wheels, a Pololu 5V Step-Up/Step-Down Voltage Regulator S18V20F5, and two Sharp distance sensors.
His Python code and more discussion are in his blog post.
Most of the products we manufacture are small electronics subassemblies, which we have been packaging in these pink antistatic bags that are probably familiar to everyone who has worked with electronics:
These bags are supposed to help prevent charge buildup and therefore help prevent the sensitive components inside from getting damaged just from the bags being shuffled around. But, if you charge yourself up and then grab the bag, you can still zap the electronics inside through the bag.
This year, we began transitioning our packaging to metalized shielding bags, like this:
These bags have the charge buildup prevention of the pink bags but also have a metal layer that prevent the spark from getting from your finger to the electronics parts in the bag. Most bags I have seen have some plastic coating outside the metal layer so that you don’t have zero resistance along the surface of the bag, but I have heard of people shorting things out by powering them up while sitting on some types of metallic bags.
Did a static discharge into a USB port cause this power supply to go up in smoke?
I once got a huge static shock when I plugged a flash drive into my USB port, and right after that, a bunch of sparks and smoke came out of my computer’s power supply. I’m pretty sure that wasn’t a coincidence, but I still can’t be sure it was a case of electrostatic discharge (ESD) destroying my computer. And usually, ESD damage is much more subtle and basically impossible for us to confirm. So, changing the packaging is one of those things where it will be very difficult to tell if it’s really doing anything. But we go through a lot of effort to inspect and test each item we make so that we can be confident it worked when we made it, so this packaging change should give us still more confidence that the part is in good condition when you receive it. It will take a while before all of our products get changed over, so don’t be shocked if your order arrives with a mix of packaging types.
Two Bit Circus is building a “micro-amusement park” in Los Angeles, and this robotic bartender will be one of the exhibits. It uses peristaltic pumps to load libations into hand-held shakers, mixes the drinks, and dispenses them. The animatronic motions of the robot are orchestrated by a Maestro servo controller and a Raspberry Pi.
More pictures and details can be found in the Make magazine article featuring the robot.
This is the first post in a series about how to make a Balboa 32U4 robot balance. Today I will talk about selecting mechanical parts for your Balboa. We offer a variety of gearmotors and wheels that work with the Balboa, and the Balboa kit includes five different gear ratios for the external gearbox, so even without considering non-standard modifications, there are many possible configurations of the robot. In this post I will give you some guidance about choosing the right parts. Continued…
Customer Carlos Ambrozak developed an “Introduction to Robotics” course that includes a lab where students work on visual object tracking. The example project is two Zumo 32U4 robots playing cat and mouse. One Zumo has a large blue ball on it and drives around avoiding obstacles. The other has a CMUcam5 Pixy on a pan-tilt mount that looks for the blue ball and follows the other robot. The Zumo 32U4 controls the camera via I2C. The lesson’s provided source code is available on GitHub.
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