Posts by Kevin (Page 3)
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Earlier this year we released a carrier for the Fairchild FPF1320, a power multiplexer that can switch between two separate power supplies, such as USB and a battery-powered 5 V regulator. The FPF1320 is great for transitioning between power sources based on an external selection signal, but by itself, it is not ideal for applications like a USB-powered microcontroller: it lacks a voltage sensor that would enable the switching to be both seamless and automatic. (By default, our carrier allows the output voltage to drop below 1.5 V whenever it switches from its preferred to alternate power source.)
That’s why we’re excited about Texas Instruments’s TPS2113A, a power multiplexer with built-in voltage sensing that supports automatic seamless switching, and today we are happy to announce the release of our TPS2113A Power Multiplexer Carrier with USB Micro-B Connector.
The switching behavior of the TPS2113A depends on the state of its VSNS input. Our carrier pulls VSNS low through an on-board pull-down resistor, which causes the multiplexer to simply select the higher of the two input sources to pass to the output. However, adding another resistor between VSNS and the primary input source creates a voltage divider that allows you to set a precise threshold voltage at which the multiplexer will switch to the secondary source.
For example, the TPS2113A could be used to build a device that is primarily powered by USB, but switches to a secondary 5 V supply as soon as the USB voltage falls below 4.8 V. Since the multiplexer can prevent its output from falling below 4.8 V during the transition, it enables the system to be seamlessly connected to and disconnected from USB without noticeable power interruptions.
The TPS2113A offers additional features that can be useful in a power supply circuit, including an adjustable current limit and a status output that indicates which power source is currently selected. Our carrier board breaks out all of the chip’s pins, making it easy to connect additional components and customize the multiplexer’s behavior for a range of applications.
We think the TPS2113A is a great power switching solution for USB devices, and we look forward to using it in upcoming designs; keep an eye out for it in our future products!
Like the LPS331AP, the LPS25H provides pressure readings over a range of 260 mbar to 1260 mbar (26 kPa to 126 kPa), and this data can be used to calculate the sensor’s altitude. Our LPS25H carrier mounts the sensor on a 0.4″ × 0.8″ board (0.1″ shorter than our earlier LPS331AP carrier) that breaks out all of its pins, and as usual, we’ve included level shifters and a regulator to make it easy to use in a 5 V system. Continued…
We posted about a Simulink library for the Zumo robot recently, and now a tutorial that teaches you how to use that library to program a Zumo robot with Simulink is available on the Adafruit Learning System. The guide walks you through setting up a Simulink model to make the Zumo follow a specific trajectory, then loading the generated code onto the Zumo to see it run.
Related post: Zumo robots programmed with Simulink by MathWorks
MathWorks, the producer of technical computing software including MATLAB and Simulink, has released a Simulink library for the Zumo robot. The library provides blocks that represent all of the sensors and peripherals on our Zumo robot for Arduino, making it possible to program an Arduino-controlled Zumo robot using Simulink.
These Simulink-programmed Zumo robots have made a few appearances on MathWorks’ MakerZone blog. This article discusses the math behind programming a robot to follow a line, modeling the control system as a harmonic oscillator.
MathWorks also used several Zumos as part of a demonstration at the Robot Zoo, part of the 2014 Cambridge Science Festival. You can read more about their Zumo demonstration, as well as their other robot exhibits, in their recap of the event.
Related post: How to program a Zumo robot with Simulink
When I first started planning a robot for the recent LVBots dead reckoning competition, it was more or less a conventional design—a flat chassis with motors and circuit boards attached to the top and bottom—and I lost interest in it quickly because it felt like I was just reinventing the 3pi. I looked for a way to make the shape of the robot unique, and I noticed that the three-legged shape of R2-D2, the famous astromech droid from Star Wars, might be a good fit for a typical undercarriage composed of a ball caster and two wheels. The result of continuing along this line of investigation is my dead reckoning robot, R2-DR (you can probably guess what DR stands for). Continued…
We’ve released an updated version of our dual VNH5019 motor driver shield for Arduino. The VNH5019 is a great solution for driving high-power motors, with each chip able to supply up to 12 A continuously at 5.5 V to 24 V. However, the original version of our dual VNH5019 shield was designed before the Arduino Uno R3 was released, so it lacked pass-throughs for the four new pins (SCL, SDA, IOREF, and an unused pin) introduced by the R3 and present on all newer Arduinos. This makes it harder to stack other shields with it, especially ones that make use of the new I²C pin location. The latest board revision adds these pass-throughs to make the shield fully compatible with the Uno R3 pinout.
On March 6, LVBots held another competition at Pololu. This time, it was a dead reckoning contest: each robot had to find a line course and follow it to its end while keeping track of its position, then try to return to its starting position without any external navigational aids. Scoring was based on how close to the starting position the robot ended up, as well as how quickly it got there. The complete rules are available here (23k pdf). You can see a selection of the entries in this video compilation from the contest.
David has already posted about his entry. My robot was R2-DR, the miniature astromech droid, and I’ll be writing a post about it soon, too.
Are you in the Las Vegas area? Check out the LVBots Meetup page and drop by this Thursday, March 20, to see the robots in person!
Updates: You can read more about each of our robots in these blog posts:
- David and Fang’s dead reckoning robot based on the mbed LPC1768
- Brandon’s dead reckoning robot
- R2-DR, Kevin’s dead reckoning robot
- Claire’s dead reckoning robot
- Paul’s dead reckoning robot
- Jon’s dead reckoning robot
- Jamee’s dead reckoning robot
When we designed the first version of the Pololu USB-to-serial adapter way back in 2004, using a USB Mini-B receptacle was an obvious choice: it was much smaller than the standard B-type connector, allowing us to keep the board compact, and it was readily available in surface-mount configurations that facilitate automated printed circuit board assembly.
We went on to use the Mini-B connector in lots of products, like our Maestro servo controllers and Wixel. Although the even smaller Micro-B connector became part of the USB specification in 2007, it didn’t seem to offer enough of an advantage over the Mini-B connector for us to immediately switch over. Continued…
We’ve started selling USB versions of these two RoboClaw motor controllers from Orion Robotics:
These new RoboClaws add a USB serial interface to the other three control interfaces available (TTL serial, RC, and analog inputs), but are otherwise identical to the V4 RoboClaw 2×15A and 2×30A controllers that we previously offered. Like their predecessors, they can drive a pair of brushed DC motors with up to 15 A or 30 A, respectively, at voltages from 6 V to 34 V. Integrated dual quadrature decoders make it easy to create a closed-loop speed control system; analog feedback is also supported for closed-loop position control.
This data logger shield from Adafruit provides an easy way for your Arduino to save data so you can process and analyze it later. It accepts any SD card formatted with a FAT16 or FAT32 file system, and it includes a real-time clock (RTC) for accurate timestamping of your data. Lots of documentation and resources are available from Adafruit to help you get started with the shield.
For more information, see the Adafruit Data Logging Shield for Arduino product page.