Posts by David

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David and Fang's dead reckoning robot based on the mbed LPC1768

Posted by David on 14 March 2014
Tags: lvbots
David and Fang's dead reckoning robot based on the mbed LPC1768

Several people here at Pololu made robots to compete in the LVBots dead reckoning competition last week. This post is about the robot I made along with another engineer here.

Dead reckoning is the process of continuously calculating your position using internal sensors that tell you something about what speed and direction you are going. In our dead reckoning competitions, robots demonstrate that they are capable of dead reckoning by following a long, twisting line drawn on the floor and then driving back to their starting point. The line functions as a user interface that directs the robots through a sequence of moves for which it was not preprogrammed. The robots are scored based on the time they took and how close they were to the starting point at the end. Continued…

Raspberry Zumo Robot

Posted by David on 6 January 2014
Raspberry Zumo Robot

Frédéric Jelmoni built a neat robot with a Raspberry Pi and a Zumo Chassis Kit. The Raspberry Zumo robot can be controlled over WiFi using telnet. The server on the Raspberry Pi is written in Python and uses the RPIO library to send signals to an SN754410 motor driver that drives the two 100:1 Micro Metal Gearmotors HP in the Zumo chassis. The server also controls an RGB LED and a buzzer. A stripped-down Logitech webcam attached to the front of the robot provides video that is streamed over the web using mjpg-streamer.

For more details, see the Raspberry Zumo page, which is written in French. Also, see our post from last October about a similar robot, the Pibot-B.

New products: Addressable RGB LED strips based on the WS2812B

Posted by David on 6 December 2013
Tags: new products
New products:  Addressable RGB LED strips based on the WS2812B

This week we started selling new addressable RGB LED strips. These LED strips are a great way to add some color to a project, and I would like to show a little bit about how they work. Here is a close up showing one segment of a new LED strip:

Close up of one segment of a WS2812B-based LED strip, with the red, green, and blue LEDs on at their dimmest setting.

At first glance, it is easy to see the RGB LED and a capacitor, but where are all the other components, such as the LED driver? Well, let’s look more closely at the LED:

Close up of a WS2812B, with the red, green, and blue LEDs on at their dimmest setting.

The LED actually has a driver built into it, which is the large brown rectangle in the picture. This driver receives high-speed color data, storing the first 24 bits it sees and passing the rest of the bits down the strip to the next LED. The driver is connected with tiny wires to the red, green, and blue LEDs. For the photos above, we turned each of the LEDs on at its dimmest setting so you can see their colors. This integrated circuit (IC) consisting of an RGB LED and a driver is called the WS2812B.

Since the WS2812B integrates an LED and a driver into the same package, we are able to offer higher density strips than before. We offer these WS2812B LED strips that have 60 LEDs per meter:

We also offer these WS2812B LED strips that have 30 LEDs per meter:

These LED strips are meant to replace the older LED strips we have that are based on the TM1804 driver (items #2543, #2544, and #2545). The older LED strips are now on clearance.

All of our example code has been updated to fully support the new strips. We provide example code for the Arduino, AVR, and mbed microcontroller platforms. More information about the LED strips and how to use them can be found on the LED strip product page.

Controlling an addressable RGB LED strip with an Arduino and powering it from a 5V wall power adapter.

Quaternion-based AHRS using AltIMU-10 & Arduino

Posted by David on 19 November 2013


Quaternion-based AHRS using AltIMU-10 & Arduino

Pololu forum user Camel recently posted the Quaternion-based AHRS using AltIMU-10 & Arduino. This is an Arduino program that can read data from our AltIMU-10 sensor board, compute the orientation of the board, and output it over serial. It uses quaternions internally to represent the rotation, but can output Euler anglers, a rotation matrix, or a quaternion. The MinIMU-9 v2 is just an AltIMU-10 without a pressure sensor, so the code can be made to work with a MinIMU-9 v2 by commenting out a few lines.

The AHRS program is part of the Firetail UAV System, an open source UAV autopilot system that is currently under development. You can follow the the project’s progress on its blog.

New product: Raspberry Pi

Posted by David on 15 November 2013
Tags: new products
New product: Raspberry Pi

We are now carrying the Raspberry Pi Model B, Revision 2.0!

In case you haven’t heard of the Raspberry Pi, it is a popular credit card-sized computer that can run Linux. It was designed by the Raspberry Pi Foundation in order to provide an affordable platform for experimentation and education in computer programming. The Raspberry Pi can be used for many of the things that a normal desktop PC does, including word-processing, spreadsheets, high-definition video, games, and programming. With its 0.1″-spaced GPIO header and small size, the Raspberry Pi also works as a programmable controller in a wide variety of robotics and electronics applications. We have seen a lot of our customers do neat things with the Raspberry Pi, and we have featured several of those projects on this blog.

Related past posts featuring the Raspberry Pi:

For more information on the Raspberry Pi, see the product page.

Wireless Servo Widget

Posted by David on 28 October 2013
Wireless Servo Widget

Pololu forum user Martan recently released a project called Wireless Servo Widget. The project website says:

Wireless Servo Widgets allow you to control up to 64 slaves, with each slave controlling up to six R/C type servos. In addition, each slave can return 3 analog input values to your Raspberry Pi. Slaves have a range of about 50 feet from the master. Use them for home automation, robotics, model train controls, or whatever you want!

The Wireless Servo Widget is based on our Wixel Programmable USB Wireless Module. Martan wrote apps for the Wixel that use the packet addressing feature of the CC2511F32 chip to implement a round-robin protocol. He also made a Slave Widget Breakout Board which makes it easy to plug servos into the slave Wixels. All of this and more can be found on the Wireless Servo Widget website.

PiBot-B: mobile robot with a Raspberry Pi

Posted by David on 23 October 2013
PiBot-B: mobile robot with a Raspberry Pi

Thomas Schoch, of Essen, Germany, built a neat robot with a Raspberry Pi and a Zumo Chassis Kit. The PiBot-B is controlled by a custom iPhone app that communicates over WiFi to the Raspberry Pi, which is running lighttpd and PHP. A Python program uses the WiringPi library to send signals to an L293D motor driver that drives the two 100:1 Micro Metal Gearmotors in the Zumo chassis. The iPhone app displays video from the attached Logitech C300 webcam, and the robot has an integrated 8×8 LED matrix from Adafruit that indicates its state. In the future, Thomas plans to add sensors for obstacle detection and make the robot autonomous. We were impressed by several things:

  • PiBot-B is very tidy, thanks in part to the USB cables that were shortened and modified using liquid rubber.
  • The Raspberry Pi has only one PWM output so Thomas used two OR gates to select whether the left motor, right motor, or both motors receive the PWM signal.
  • The write-up has some great photos and informative diagrams.

The PiBot-B page is written in German, but it has a link at the top to translate it into English using Google Translate.

Programming resources for the Maestro servo controllers

Posted by David on 16 September 2013


Programming resources for the Maestro servo controllers

Writing a computer program to interface with a USB device from scratch can be tough. Luckily, many users of our Maestro Servo Controller who have tackled this problem have been kind enough to share their results with the community. Example code for interfacing with the Maestro is available for over a dozen platforms: Arduino, C, C++, C#, LabVIEW, MATLAB, Node.js, Perl, PHP, Python, Visual Basic 6, Visual Basic .NET, and Visual C++.

You can now find all of this, and more, in the new Related Resources section of the Maestro User’s Guide, which we added last week. The new section also links to tutorials, example projects, and commercial software that is integrated with the Maestro. We hope this will make your next Maestro project easier!

Node.js module for Maestro servo controllers

Posted by David on 9 September 2013
Node.js module for Maestro servo controllers

The node-pololumaestro project is a module for the Node.js platform that allows you to control a Maestro USB Servo Controller over its serial interface from a Node.js program. This module provides functions like maestro.setTarget(0, 1500) and internally takes care of assembling the bytes of the serial command for you. The module was written by Owen McAree and was recently expanded by achingbrain. We always like to see our customers helping each other through projects like this!