Pololu Blog (Page 32)
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.
On May 29, LVBots held a maze solving competition at Pololu. The goal in maze solving is to get from the start to the finish in the shortest time. Contestants had four tries to solve the maze. The first run is typically in a learning mode where the robot goes slowly and explores the maze. On subsequent runs, the robots would attempt the shortest path, and the best robots had progressively more aggressive speeds.
I would have liked to see one of the custom-built robots win, but despite their best attempts, none of the other competitors were able to beat a stock 3pi robot running Ben’s maze solving code from six years ago. The old video below demonstrates how the 3pi solves a maze and also describes how the course is built.
This year, we tried to hone our rules about robots cutting corners of the maze. No robot will follow the line perfectly, so we have to allow some corner-cutting, but we do not want to make it so lax that the robot could dead reckon directly to the finish. After a lot of debate, we settled on two rules:
- A designated point on the robot must not go past the walls of an imaginary 6″-wide corridor centered around the path.
- The whole robot needs to generally follow the same path through the maze.
It was exciting to see Paul’s robot, Dr. Maze, use dead reckoning to cut the corners. Paul was hoping to get away from line following and rely on encoders to navigate the maze. Unfortunately, this caused the robot to get lost on the long straightaway and fail to solve the maze. Dr. Maze exhibits its corner-cutting skills at the end of the first video.
Are you in the Las Vegas area? Check out the LVBots Meetup page to get involved.
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).
Guido Bonelli Jr. of Innovative Electronic Solutions LLC created the ORBIS Wooden Kinetic and Lighting Sculpture for a client’s home using our custom laser cutting services. ORBIS hangs at 24″ in diameter and is 3/4″ thick. We laser-cut the parts from 1/8″ and 1/4″ baltic birch plywood, which were stained before assembly.
The separate control box and the wall unit each contain an Arduino Mega 2560 and an XBee module for wireless communication. The control box allows users to pick between two modes to control different features of the sculpture: kinetic mode allows users to adjust the rotating speed and direction of the two rings of the sculpture, and the color changing mode allows users to select various automated color patterns or control the red, green, and blue values individually to pick from 16 million colors.
For more information about ORBIS, check out the project’s web page.
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.
The Beatty family is at it again with their amazing robot builds (if you missed it, check out their Mars Rover). They completed Aluminalis, a sixteen-legged walking robot made mostly out of machined aluminum components.
The video above shows their magnificent sixteen-legged walking robot. It is all controlled by an Arduino Nano and uses Pololu 20D 73:1 metal gearmotors with matching brackets to move all of its aluminum legs.
For more information on Aluminalis, check out its build page.
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.
Forum user patman715 posted to the forum about his modified Zumo Robot. The video above shows a Zumo with a two-servo gripper and arm capable of lifting tennis balls into an on-board storage bin. It is all controlled by an Arduino Leonardo, and two of our 100:1 micro metal gearmotors (we suspect they are HP versions) seem to give it plenty of oomph for carrying around the extra load.
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.
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…