Posts by Brandon
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@MarcisShadow is working on a project using a Raspberry Pi with a Pololu DRV8835 Dual Motor Driver Kit for Raspberry Pi to control a Celestron NexStar GoTo Mount, allowing web-based control of a telescope. He also uses a Pololu 5V Step-Up/Step-Down Voltage Regulator S7V7F5 connected to the motor driver to power the Raspberry Pi from the motor power supply.
The project is being documented in a multi-part series on DirtyAstro.com. Part 1 covers the electronics that come with the telescope mount, part 2 is about assembling and testing the DRV8835 driver kit and motors, part 3 tackles setting up the Raspberry Pi and using an SSH client (PuTTY) to connect to it remotely via a PC, and part 4 is about getting Node-Red running to program the Raspberry Pi graphically using a web interface from any machine on the network.
He is not finished with the project, but I have a couple of suggestions for him or anyone doing something similar: First, since his 12 V supply exceeds the maximum operating voltage of both the motor driver (11 V) and the regulator (11.8 V), I would recommend using different ones. Keep in mind that “wall-wart” DC power supplies, especially older transformer-based ones, can have a voltage significantly higher than the rated voltage. Second, a board running a full operating system is usually not great for timing-sensitive operations like counting encoder ticks. If it can’t keep up with the pulse rate, I would recommend using a secondary microcontroller for the encoders. One possibility would be to use the A-Star 32U4 Robot Controller SV with Raspberry Pi Bridge, which incorporates a more appropriate 5.5 V – 36 V regulator, an Arduino-compatible microcontroller, and dual motor controllers.
Forum user ZipZaps shared a fantastically charming project that uses a 24-channel Maestro servo controller to automate a Smith Corona typewriter using the speech recognition built into Windows. The Maestro controls a mechanism consisting of multiple rows of servos on some small linear rails to strike the keys in a manner resembling the way a person would normally interact with the typewriter. An Arduino paired with a Big Easy driver controls the stepper motor used to slide the carriage return system.
You can find more pictures and information about this project in ZipZaps forum post.
The Bolide Y-01 DIY kit from XYZrobot comes with all of the components needed to build this advanced humanoid robot, including a Bluetooth controller, an Arduino-compatible ATmega1280 microcontroller, sensors, and 18 A1-16 smart servos. The ATmega1280 microcontroller comes preprogrammed to perform a range of complex movements, including dancing, walking and standing up in response to commands from the included Bluetooth remote or a smartphone or tablet running the XYZrobot app. The control board includes a three-axis accelerometer for maintaining postural stability and detecting falls, and the robot also has a distance sensor in its chest that can detect objects in front of it. For those interested in expanding the capabilities of this robot beyond the preprogrammed routines, the Bolide Y-01 control board can be programmed with the Arduino IDE and the XYZrobot Editor software. You can find more details about the Bolide Y-01 advanced humanoid robot DIY kit on its product page.
We are perhaps even more excited about carrying the A1-16 smart servos separately. These specialty servos are well suited for applications such as humanoid robots, hexapod robots, and robotic arms that require strong and complex actuation. Unlike the usual RC hobby servos, these servos are not only capable of 360° continuous rotation, but they also offer position control over an effective 330° range. To achieve this kind of motion, they use a TTL serial interface, which also allows them to be daisy chained and controlled from the same serial bus (this is their only method of control, so they will not work with standard RC receivers and servo controllers). In addition, these smart servos provide additional feedback such as position, speed, and temperature! The four-color LED featured on each servo is used as a visual error indicator by default, which is really handy to quickly determine if servos in a chain are experiencing a problem. Alternatively, this LED can be manually controlled through the serial interface. See the A1-16 smart servo product page for more information about this feature-packed servo.
We are rolling out another set of new products here at Pololu: Scooter/Skate Wheels. They are available in 144×29 mm, 100×24 mm, 84×24 mm, and 70×25 mm sizes, offering larger alternatives to our line of Pololu Wheels. They are compatible with standard 608 bearings, so they also work with our Aluminum Scooter Wheel Adapters, which make it easy to connect these wheels directly to an assortment of motors for use in robot drive systems:
You can find more information about these wheels on their product pages:
Helen Lawson designed and built a one-sixth scale Mark 1 British Heavy Tank replica that is a functional, radio controlled robot. The replica has been a work in progress for around three years and is now reaching completion. Helen designed the main chassis out of laser-cut wood and made other aspects of the chassis from aluminum and 3D printed parts.
One distinguishing feature of a MK 1 British Heavy Tank is the lack of a central turret. Instead, it has a sponson on each side. This proved challenging for Helen’s build since most electronics made for RC tanks only allow for a single gun and turret. To make the sponsons functional, Helen used a combination of an RC receiver, an RC switch with digital output, an RC switch with relay, a Micro Maestro servo controller, a few servos, and a Taigen gun flash unit. You can find more detailed information about this part of the system (including a wiring diagram and Maestro script) in her post on our forum. The images below show each side of one of the completed sponsons:
She also made a 3D-printed case for the Maestro (shown in the photo on the right) and a few of the other electronic components, which she made available on her Thingiverse page.
You can see a video of the robot in action on this Portsmouth Model Boat Display Team Armoured Division Facebook page, and even more information on her build, including many more pictures, in Helen’s forum thread at landships.net.
Before I started designing my entry into this year’s LVBots mini sumo competition, I watched several videos of other competitions. I noticed a majority of the victories came from engaging the opponent from the side or back; a pattern I also noticed during the last LVBots mini sumo competition. For that competition, I made a robot that used a blade and sensors on the front and back of the robot (basically making the robot have two fronts and no back). However, my strategy in that competition was to roam the ring and search for the opponent, which I suspect increased the chances of the opponent engaging from a suboptimal angle. This time, I wanted to try having my robot spin in place looking for the opponent and striking once it was found. This ultimately resulted in my newest mini sumo robot, Black Mamba. For those unfamiliar, a black mamba is a snake with a reputation for being highly aggressive and is one of the longest and fastest-moving snakes in the world. A black mamba’s venom is highly toxic, and it is capable of striking at considerable range, occasionally delivering a series of bites in rapid succession. Black Mamba is also Kobe Bryant’s self-appointed nickname (yes, I am a Lakers fan). Continued…
Jay Doscher posted on his blog at Polyideas.com about his 2-axis solar tracker designed to provide the optimal amount of power output with a portable setup. In the build, Jay uses a Raspberry Pi A+ topped with our Dual MC33926 Motor Driver for Raspberry Pi to control the motion of the system, which is accomplished using a Concentric 4″ linear actuator with feedback. In lieu of a GPS unit, the tracker uses hard-coded longitude and latitude coordinates with Pysolar, an open-source Python library, to calculate the sun’s predicted position. The system keeps the solar panel pointed at the calculated position with the help of a Razor IMU from SparkFun. The video above is time lapse footage of a mechanical test of the system that shows the unit tracking the sun (although it is indoors).
In the picture above, you can see the Raspberry Pi and dual MC33926 driver board on the left and the IMU on the right. The Dual MC33926 Driver for Raspberry Pi fits on top of the Raspberry Pi mainboard, eliminating a lot of wiring and making it easy to use while also leaving the setup looking clean and organized. Additionally, the Dual MC33926 Driver for Raspberry Pi provides a set of three through-holes where an appropriate voltage regulator can be conveniently connected, allowing the motor supply to also power the Raspberry Pi. You can see one of our D24V10F5 switching step-down regulators mounted on top of the dual MC33926 driver board to serve this purpose in the picture above as well.
This project was also a 2015 Hackaday Prize entry and made it to the quarterfinals!
For more information about this project, see Jay’s blog post, which has additional photos and details including a parts list and links to his code.
A contact at Mexican distributor Cosas de Ingeniería wrote to let us know about a contest he is helping organize in Juriquilla, Querétaro, Mexico. The Mexican Mechatronics Asociation (Asociación Mexicana de Mecatronica A.C.) will be hosting the 14th National Congress of Mechatronics (14º Congreso Nacional de Mecatrónica) 2nd Robotics Competition on October 15th through 17th this year. The three-day event will host several robotic competitions:
- Autonomous Vehicle Competition (based on the Sparkfun Autonomous Vehicle Competition)
- Insect Robot Race (insectoid robots try to be the first to travel 2 m over obstacles and uneven surfaces)
- Mini-Sumo Competition (autonomous robots, similar to the one pictured above and our Zumo robots, fight to stay in a designated area)
- Line Following Competition (autonomous robots follow a line-marked course as quickly as they can)
In September of last year, we started carrying our Breakout Board for microSD Card, which was the first board that I ever designed and routed here at Pololu. It is a simple breakout board that gives direct access to each contact available on a microSD card socket. However, since microSD cards operate at 3.3 V, it can be tricky interfacing them with a 5 V system. To address this, we made a new version with an integrated 3.3 V regulator and level shifters. Even with the extra components (and mounting holes, which the mechanical engineers at here Pololu are always pushing for), the board is still compact, measuring only 0.94″ × 0.9″, and it breaks out all of the contacts from a microSD card socket necessary to interface with the card through its SPI bus mode interface to a single 1×9 row of 0.1″-spaced pins. This allows easy use with breadboards, perfboards, or 0.1″ connectors.
You might recognize the circuit from our A-Star 32U4 Prime controllers, which use essentially the same level shifters to interface a microSD card with an Arduino-compatible ATmeg32U4 microcontroller running at 5 V.
For more information about this breakout board, see its product page.
For the recent LVBots line following competition, my first instinct was to try to come up with some unique alternative design for a robot that would be competitive with the traditional differential drive robots. However, I knew the winning robot from the last LVBots line following competition (Mostly Red Racer) would be returning, and it had an impressive time to beat. I also remembered spending so much time designing and assembling the hardware for my last line following robot, that I ended up not having enough time to tune the PID coefficients and get the performance I was hoping for. After brainstorming a few ideas, I ended up deciding to keep it simple and make sure I had enough time to get a robot I was happy with, which I ultimately named “The Chariot” because of its shape. The Chariot ended up winning second place in the competition, which I was very happy with. Instead of focusing this blog post on how you can make your own version of The Chariot, I will try to explain my thought process throughout the design and build process, In other words, my hope is that after reading through this post, it will be clear why I chose the parts that I did. Continued…