Posts by Ben (Page 6)
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We have some very exciting price reduction news to share with you, but first:
A little background
|3-axis accelerometer carrier, released 22 Apr 2008.|
MEMS (Micro-Electro-Mechanical Systems) devices are everywhere today, from airbag crash sensors to smartphones to inkjet printer heads, so it is easy to take this ubiquitous technology for granted without considering just how impressive it really is. The defining characteristic of a MEMS device is the presence of microscopic mechanical elements that are similar in size to the features of the electronics in an integrated circuit – if you look closely enough at the silicon of a MEMS inertial sensor, you will see tiny moving cantilevers or springs right alongside the electrical elements that let you interface with them.
Several of us here at Pololu fondly remember using our first MEMS sensors around the turn of the century (the “Y2K” one, not the horse-and-buggy one) as they became affordable enough to consider for our college engineering projects. At the time, it was around $20 for a single-axis accelerometer, and that seemed like a pretty sweet deal! Since then, widespread use of MEMS technology in mobile devices has led to rapidly improving performance and falling prices, putting some amazing technology well within the financial reach of students and hobbyists. However, these same market pressures favor compact, surface-mount ICs that can be integrated into ever-shrinking consumer products, making them very difficult to work with, and this is where we come in: our goal is to make these great sensors available to a much wider audience. We design and manufacture breadboard-compatible carrier boards for these MEMS ICs that include all of the additional required components along with voltage regulators and level-shifters that allow direct integration into 5V systems.
One side effect of this rapidly evolving technology is that if we want our MEMS products to remain relevant, we have to update them more quickly than our other products. For instance, our 3pi is approaching six years old, yet it is still a decent basic robot platform (see my stock 3pi dominate our recent LVBots maze-solving competition). In that same time, we have gone from our first MEMS carriers – a 3-axis accelerometer for $20 and a single-axis gyroscope for $30 – to a complete IMU with 3-axis accelerometer, 3-axis magnetometer, 3-axis gyro, and pressure sensor, each with performance much better than those earlier units.
So far, we have generally kept our prices the same or had modest decreases as we have released newer units with higher performance, but today we are announcing significant price cuts to our latest-generation boards:
The LSM303D 3D compass and accelerometer carrier is now $9.95, down from $14.95. This inertial sensor consists of a 3-axis accelerometer and a 3-axis magnetometer in a single package.
The L3GD20H 3-axis gyro carrier is now $12.95, down from $19.95. This inertial sensor measures the angular rates of rotation about the roll, pitch, and yaw axes.
The MinIMU-9 v3 is now $19.95, down from $39.95. This IMU module features an LSM303D 3D accelerometer+magnetometer and L3GD20H 3D gyro, providing nine independent rotation, acceleration, and magnetic measurements that can be used to calculate the module’s absolute orientation.
The AltIMU-10 v3 is now $27.95, down from $49.95. This IMU module is equivalent to a MinIMU-9 v3 with an integrated LPS331AP pressure sensor, providing ten independent pressure, rotation, acceleration, and magnetic measurements that can be used to calculate the module’s altitude and absolute orientation.
This fast technology progression makes planning challenging – it sometimes takes six months or more from the time we order a newly-announced component to when it arrives, and by the time we get it and build a board around it, the next great part is announced. This leads to a somewhat complicated lineage of products in various life-cycle stages. The following diagram shows the progression of our products based on ST’s MEMS sensors, which we have been most excited about lately thanks to their digital interfaces and many user-configurable settings:
|Evolution and release dates of Pololu carriers for ST’s MEMS sensors through May 2014.|
The constant product refreshing also leaves us with older-generation boards that we generally put on clearance. We have decreased the clearance prices of these products so they remain compelling lower-price alternatives to the latest-generation boards. These boards are not recommended for new designs where continued availability is important, but if you just want to play around with a cheap sensor that was state-of-the-art a few years ago, these are a great deal while they last:
The LSM303DLM 3D compass and accelerometer carrier has a new clearance price of $5.95.
The LSM303DLHC 3D compass and accelerometer carrier has a new clearance price of $7.95.
The L3GD20 3-axis gyro carrier has a new clearance price of $9.95.
The MinIMU-9 v2 has a new clearance price of $14.95. This IMU module features an LSM303DLHC 3D accelerometer+magnetometer and L3GD20 3D gyro.
The AltIMU-10 has a new clearance price of $22.95. This IMU module is equivalent to a MinIMU-9 v2 with an integrated LPS331AP pressure sensor.
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.
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.
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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.|
A few months ago, we introduced our new D24V5Fx buck (step-down) voltage regulator family with inaugural members offering fixed output voltages of 3.3 V, 5 V, 9 V, and 12 V, and now we have expanded that family by adding versions with fixed output voltages of 1.8 V, 2.5 V, 6 V, and 15 V.
We are particularly excited about this regulator family because of its wide operating voltage range, high efficiencies, and low dropout voltages, all in a compact 0.5″ × 0.4″ × 0.1″ (13 mm × 10 mm × 3 mm) form factor that is smaller than standard through hole linear regulators with DIP packages. For example, the picture below shows a D24V5Fx next to a 7805 voltage regulator in a TO-220 package:
These regulators operate at up to 36 V, making them especially useful in applications where there can be large variation in the input voltage, such as solar-powered systems or devices where power supply flexibility is a benefit. Since they are switching regulators, the efficiency is much higher than linear regulators when there is a big difference between the input and output voltage, and since they are synchronous, the efficiency is high even at light loads and low output voltages. As an example of the versatility of these regulators, the same D24V5F2 module can in one application be used to get 2.5 V from a 24 V battery and in another be an efficient way to add a 2.5 V node to a system that already has regulated 5 V. As the performance graph below shows, typical efficiency in the latter scenario is 90%, which could almost double battery life in portable systems when compared to linear regulators.
We consider the new D24V5Fx regulators to be next-generation alternatives to our D24V3Fx and D24V6Fx buck regulators, which have been some of our most popular products. In addition to having generally higher efficiencies (which in practice allow these 500 mA units to achieve maximum output currents comparable to our 600 mA D24V6Fx units), these new regulators have much lower dropout voltages (“dropout voltage” is the amount by which the input voltage must exceed the output voltage in order to ensure that the target output can be achieved). For example, the two graphs below show the dropout voltage of the new 5 V D24V5F5 compared to the older 5 V D24V6F5 and D24V3F5:
What this means for your project is broader operating ranges and longer battery life. For instance, a low-power 5 V system running on a 9 V battery can discharge it all the way to 5 V whereas the higher-dropout D24V6F5 regulator can only go to 6.5 V, and four-cell alkaline and five-cell NiMH packs (both with 6.0 V nominal voltages) become viable options.
We are now carrying metal servo horns that work with Power HD’s ultra-high-torque HD-1235MG giant servos, which can deliver a whopping 560 oz-in (40 kg-cm) at 7.4 V. If you want to get the most power out of your HD-1235MG, I recommend substituting one of these anodized aluminum horns for the included plastic horns.
Get FREE copies of Circuit Cellar magazine’s May issue and Elektor magazine’s May issue with your order, while supplies last. To get your free issues, enter the coupon codes CIRCUIT0514 and ELEKTOR0514 into your shopping cart. The magazines will add 6 ounces and 7 ounces, respectively, to the package weight when calculating your shipping options.