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We posted recently about how progress in MEMS sensors has resulted in a constant stream of improved Pololu breakout boards. This week, we brought some of that technological progress to our Zumo robot with the release of a new “v1.2” version of the Zumo Shield for Arduino. This new version upgrades the previously-included LSM303DLHC compass to nine channels of inertial sensing using the newer LSM303D compass and L3GD20H gyroscope.
That means that the new Zumo shield includes a full inertial measurement unit (IMU) – the equivalent of a MinIMU-9 v3 – letting you turn it into a complete AHRS by adding an Arduino or compatible controller.
The v1.2 update extends to three new products:
- Zumo Shield for Arduino, v1.2
- Zumo Robot Kit for Arduino, v1.2 (No Motors)
- Zumo Robot for Arduino, v1.2 (Assembled with 75:1 HP Motors)
Other parts, such as the Zumo chassis, sumo blade, and reflectance sensor array, are not affected by this update, and the new Zumo shield is mechanically and electrically compatible with the previous model. They are also completely code-compatible except for the MEMS sensor aspects, which are already supported by our open-source Arduino libraries.
Two weeks ago, we announced a big price reduction of our MEMS-based sensors and explained a little about why we release new versions of these boards so frequently. If you looked closely at the diagram showing the evolution of our ST MEMS sensor boards, you might have noticed that we’ve used each IC on a carrier board for that chip by itself, as well as on an IMU board combined with other sensors, with one exception: the LPS25H pressure sensor. When that post was written, we had recently released our LPS25H carrier, but we did not yet offer an IMU featuring this new barometer IC. The AltIMU-10 v3, which uses the older LPS331AP pressure sensor, was the newest AltIMU available from us at the time.
With the release of the AltIMU-10 v4 this week, that updated IMU is now available. Like the v3 version, the AltIMU-10 v4 contains an LSM303D three-axis magnetometer and accelerometer and an L3GD20H three-axis gyro, and it replaces the LPS331AP pressure sensor on the older board with the improved LPS25H, enabling pressure and altitude measurements with higher accuracy and lower noise.
We think the AltIMU-10 v4 combines the state of the art in ST’s MEMS sensors into one compact module at a great price. However, we’ve also put the AltIMU-10 v3 on clearance and lowered its price; if you don’t absolutely need ST’s newest pressure sensor on your IMU, the v3 is still a very good sensor board to consider.
Here’s an updated version of our diagram showing where the new AltIMU-10 fits in:
|Evolution and release dates of Pololu carriers for ST’s MEMS sensors through June 2014.|
We’re now selling the UM7-LT orientation sensor, the latest Attitude and Heading Reference System (AHRS) from CH Robotics. The UM7 takes advantage of newer sensor technology to offer improved performance compared to its predecessor, the UM6, despite its reduced cost.
Like earlier CH Robotics AHRS modules, the UM7 contains an onboard microcontroller that combines data from its three-axis accelerometer, gyro, and magnetometer to produce orientation estimates 500 times a second. The attitude and heading information, available in the form of Euler angles or quaternions, can either be streamed automatically or provided upon request through a TTL serial interface.
Power and serial connections can be made to the UM7-LT through a five-pin connector and an included matching cable, and expansion headers provide additional interfaces like SPI and a secondary UART that can be connected to an external GPS module. The free CHR Serial Interface software makes it easy to visualize data from the UM7 and configure its settings.
We designed these new stamped aluminum L-brackets specifically for our larger Pololu plastic gearmotors (228:1 offset, 120:1 offset, 200:1 90-degree, and 120:1 90-degree). There are two versions of this L-bracket to choose from – a compact version and an extended version, which allows for a wider variety of mounting options. The brackets are sold in pairs and come with the hardware required to secure a motor to each bracket. As a bonus, they are also compatible with the Solarbotics plastic gearmotors (GM2, GM3, GM8, and GM9) and make great alternatives to the GMB39 and GMB28 brackets.
See the product pages for additional information:
- Pololu Stamped Aluminum L-Bracket Pair for Plastic Gearmotors
- Pololu Extended Stamped Aluminum L-Bracket Pair for Plastic Gearmotors
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!
Continuing with our recent LED product line expansion, we now offer several of Adafruit’s NeoPixel rings. These addressable RGB LED rings are available in a 1.75″-diameter 16-LED ring, a slightly larger 24-LED ring, and as 15-LED quarter-rings that can be assembled into a large 60-LED ring.
The NeoPixels are effectively WS2812B RGB LEDs that are individually addressable and controllable by a single digital pin from a microcontroller. Multiple rings can be chained together, and the rings can be chained with our other WS281x-based LED products. The animated picture below shows the three different sizes of rings we carry connected in a single chain and controlled by a single pin from an A-Star 32U4 Micro, which is small enough to fit completely within the smallest ring.
|A chain of addressable RGB LEDs (#2535 and #2536) on a breadboard, controlled by an A-Star 32U4 Micro.|
At first glance, these new LEDs look like everyday through-hole RGB LEDs, but they are hiding something very special inside: a built-in WS2811 LED driver that lets you chain them together and individually control them all with a single digital output from a microcontroller. The communication protocol of these LEDs is very similar to that of our WS2812B-based LED strips and Adafruit’s NeoPixels (such as those on the Adafruit NeoPixel Shield, which we just started carrying last week), so there is a variety of sample code available for the Arduino, AVR, and mbed microcontroller platforms to help you make your project start blinking quickly.
|Two different sizes of addressable RGB LED. From left to right, their diameters are: 5 mm (#2535) and 8 mm (#2536).|
I love LEDs and all of the shiny, blinky, colorful things you can do with them (see what we did to my house last Christmas), so you can imagine how happy it makes me that we are now carrying Adafruit’s NeoPixel Shield for Arduino! With 40 individually addressable, WS2812B-based RGB LEDs all controlled by a single Arduino pin, this shield is effectively like a grid version of our addressable RGB LED strips. And just like our LED strips, multiple NeoPixel shields can be chained together into larger arrays. Controlling the LEDs is easy with the help of the compatible Arduino libraries, which include the Adafruit NeoPixel and NeoMatrix libraries, as well as our Arduino library for addressable RGB LED strips. This shield is a great way to add color, style, or functionality to your next Arduino project!
For more information on the NeoPixel shield, see the product page.
Get FREE copies of Circuit Cellar magazine’s June issue and Elektor magazine’s June issue with your order, while supplies last. To get your free issues, enter the coupon codes CIRCUIT0614 and ELEKTOR0614 into your shopping cart. Each magazine will add 6 ounces to the package weight when calculating your shipping options.
Continuing with our recent theme of tiny new actuators, we are now carrying FS90R micro continuous rotation servos from FEETECH. Continuous rotation servos are standard hobby RC servos that have been modified for open-loop speed control instead of their usual closed-loop position control, and they make convenient drive systems for robots because they are effectively a motor, gearbox, and motor controller/electronic speed control (ESC) in a single compact package. They are also very easy to use as they can be connected directly to an RC receiver or controlled by a single microcontroller I/O line programmed to output RC servo pulses.
With a weight of just 9 g, the FS90R is the smallest servo we have come across that is manufactured specifically for continuous rotation. It has great speed and torque for its size (up to 130 RPM and 1.5 kg-cm at 6 V), and at only $5 per servo, it is a very simple and affordable way to add some motion to your next project. For comparison (or if you are looking for an alternative servo that offers position control), it is very similar in size, weight, speed, and torque to the Power HD Micro Servo HD-1900A.
For more information on the FS90R micro continuous rotation servo, see the product page. For other options, you can check out our full selection of continuous rotation servos or our entire RC servo category.
|Continuous rotation servo size comparison. From left to right: SpringRC SM-S4303R, Power HD AR-3606HB, Parallax, and FEETECH FS90R.|