Lighting and Motor Control Shields for Arduino

Arduino enthusiasts will be excited to learn that Infineon Technologies has announced two new shields for RGB lighting and motor control. You can use the shields—which are compatible to Arduino Uno R3—with the XMC1100 Boot Kit, which is equipped with a 32-bit microcontroller of the XMC1000 family (uses the ARM Cortex-M0 processor).

Infineon-Arduino

Infineon RGB XMC1202 for Arduino

The RGB LED Lighting Shield for Arduino features an XMC1202 microcontroller with its Brightness Color Control Unit (BCCU) for LED lighting control. The high-current DC Motor Control Shield for Arduino contains the Infineon NovalithIC BTN8982TA integrated half-bridge driver for motor control.

The RGB LED Lighting Shield evaluation board enables you to use different LED light engines for fast prototyping. It has three independent output channels for flicker-free control of multicolor LEDs. The BCCU automated hardware engine provides a cost-effective LED lighting solution dimming and color mixing. You can expand the shield with a DMX interface for lighting and audio nodes or a 24-GHz radar sensor for motion detection.

The DC Motor Control Shield with BTN8982TA simplifies the prototyping of DC motor control designs. It can drive two unidirectional DC motors or one bidirectional DC motor. The shield features two NovalithIC BTN8982TA fully integrated high-current half-bridge drivers optimized for motor drive applications. The BTN8982TA includes three ICs: two power chips (one p-channel high-side MOSFET and one n-channel low-side MOSFET) and an integrated driver IC with one logic circuit to control and monitor the power. Other features include are diagnosis with current sense and slew rate adjustment.

Until end of January 2015, both the RGB Lighting Shield with XMC1202 for Arduino and the DC Motor Control Shield with BTN8982TA for Arduino will be available for purchase from Newark element14. After that, they’ll also be available from Infineon and its distributors.

Source: Infineon

Robotics & Intelligent Gaming

When Alessandro Giacomel discovered Arduino in 2009, he quickly became hooked. Since then, he’s been designing “little robots” around Ardunio and blogging about his work and findings. In this interview, Alessandro tells us about his most interesting projects and shares his thoughts on the future of robotics, 3-D printing, and more.

CIRCUIT CELLAR: How long have you been designing embedded systems and what sparked your interest

ALESSANDRO: I have been designing embedded systems for about five years. My interest arose from the possibility of building robots. When I was a kid, I found robots extremely fascinating. The ability to force matter to do something we decided always seemed to be one of the main goals conceded to man.

CIRCUIT CELLAR: Tell us about your first design.

ALESSANDRO: My first embedded system was an Arduino 2009. The availability of a huge shield, sensors, and actuators has enabled me to design many applications at an acceptable price for an amateur like me.

DIYrobot

Alessandro’s first robot

I started like many people, with a robot on wheels moving around avoiding obstacles. It’s a standard robot that almost all beginners build. It’s simple because it is built with only a few components and a standard Arduino 2009. The design included modified servomotors that can rotate 360° moving the robot and connected to the wheels and a servomotor to move a little head where there is an ultrasonic distance sensor. The distance sensor lets you know when the robot is in front of an obstacle and helps you decide the most convenient way for the robot to escape.

In its simplicity, this robot enables one to understand the basics for the development of a microcontroller-based robot: the need to have separate power supplies for the motors’ power circuits and for the microcontroller’s logic, the need to have precise sensor reading timing, and the importance of having efficient algorithms to ensure that the robot moves in the desired mode.

My first robot took me a long time to build. But all the elements of the robot (hardware and software) were developed by me and this was important because it let me begin to face the real problems that arise when you are building a robot. Today there are many resources on the Internet that enable one to build a robot simply replicating a set of steps anyone has described. These guides should be used as a source of inspiration, never followed exactly step-by-step, otherwise—while in the end it is true that you can build a robot—you don’t own the knowledge of what has been done.

My robot evolved with the ability to speak, thanks to a sound module. When I build a robot the goal is always to experiment with a technology and to have fun. My friends have enjoyed seeing the robot turning around, speaking, and telling funny stories.

CIRCUIT CELLAR: Your blog, Robottini (http://robottini.altervista.org), is described as “little robots with Arduino.” What inspired you to begin the blog

ALESSANDRO: I strongly believe in sharing knowledge and open-source hardware and software. I thought it was normal to try to share what I was designing when I started to build robots. When I started, I had the benefit of what others had made and published on the Internet. I thought about writing a blog in my language, Italian, but I thought also it would be a good exercise for me to try to write in English and, most importantly, this enabled me to reach a much wider audience.

The site description includes the philosophy at the basis of the blog: small robots built using Arduino. I build small robots because I’m an amateur and my house isn’t very big, so I only build robots that I can put in an armoire. I use Arduino because it is a microcontroller developed in Italy, it was obvious for me to use it, and it is really a great board for a beginner—inexpensive and robust.

ArduinoRobot

Alessandro’s first robot at the Arduino Day 2011 event

The community has developed thousands of applications that can be reused. When I started the blog in 2011, I was building small robots for a few years. In the beginning, finding information was much more complicated and there were few shields that were not cheap. So, I always tried to use “poor” materials (e.g., recovered or recycled). Decreasing the cost of implementation and reusing and imagining new purposes for the things already available in a normal house seemed like a good way to work.

My achievements documented in the blog are never step-by-step guides to build the robot. I include a list of components to buy, the source code, and sometimes the wiring diagram. But I never provide a complete guide, since I think everyone should try to build their own robot because, once built, the satisfaction is enormous.

Through my blog I am available to help with problems people encounter when they are building robots, but I think it is important to give people the tools to build, rather than providing detailed explanations. Everyone can learn only by fighting the difficulties, without having someone preparing everything perfectly.

CIRCUIT CELLAR: Robottini obviously includes quite a few robotics projects. Why did you build them? Do you have a favorite?

ALESSANDRO: Many times people ask me what is the meaning of the robots I build. The answer that I give them leaves people puzzled. The answer is this: My robots are useless. They are useful only as fun—as a passion. I’m happy when I see my little son, Stefano, who is three years old, watching and laughing at a robot turning around in our house. But this does not mean I don’t follow a branch of research when I build robots.

Initially, I built robots to understand how the driver for the motors works, the sensors, and the problems related to the logic of the robot. Afterward, the first branch of research was the issue of control, how to set the proportional, integral, derivative (PID) control to follow a line or make a robot that is in balance. This has enabled me to address the management of complex sensors, such as the inertial measurement unit (IMU).

To have a robot balance on two wheels it is important to measure how much the robot is tilting from the vertical. To do this, typically a cluster of sensors is used, called IMU, which are based on multi-axes combinations of precision gyroscopes, accelerometers, magnetometers, and pressure sensors. In a more simple version, the IMU uses an accelerometer and a gyroscope, and it is mandatory to use both signals to obtain a correct value of the tilt angle from the vertical (it is called fusion of signals).

The most common method used is based on the Kalman filter, which is a mathematical tool that enables you to combine two or more signals to obtain the value of the angle. But it is a highly sophisticated and difficult for an amateur to understand, and it requires fairly advanced knowledge of mathematics. A new method that is rather simple has been proposed in the last years. It is called the “complementary filter.“

One of the studies I performed and posted on my blog compares in practice the signals of the two filters to verify if the complementary filter is able to approximate the Kalman filter in typical situations coming up in robotics. This post has had a great following, and I’ve been surprised to see that several university-level scientific publications have linked to it. I only wrote the post because I was curious to see a simple and almost trivial method that has become helpful to researchers and hobbyists. It has been a pleasure for me.

In the last year, I have followed the trend of art and interaction (i.e., the possibility of building something that can somehow marry art with technology). It was the theme of the stall I had at Maker Faire Europe in Rome, Italy, in October 2013. Arduino is an electronic circuit without a heart and without a soul. Can an Arduino be an artist? I’m trying to do something with Arduino that could be “art.” The arts include painting, poetry, music, sculpture, and so on. I’m trying to do something in different fields of art.

My first experiment is the Dadaist Poetry Box, which is a box capable of composing and printing Dadaist poems. It’s made with an Arduino and uses a printer for receipts to write poems. The box uses an algorithm to compose the poems in autonomy. You push the button and here is your Dadaist poem.

PoetryRobot

Dadaist poetry box design

Normally, the poem is a valuable asset, the result of an intimate moment when the poet transposes on paper the emotions of his soul. It is an inspired act, an act of concentration and transport. It’s not immediate. The poem box instead is trivial, it seems almost “anti-poem.” But it’s not; it’s a Dadaist poem. A user can push the button and have an original poem. I like the machine because it gives everyone something material to take home. In this way, the experience of interaction with the machine goes beyond the moment.

Another of my favorite robots is one that is capable of drawing portraits. I’ve never been good at drawing, and I’ve always been envious of those who can easily use a pencil to make a portrait. So I tried using my technical skills to fill this gap.

DrawingRobot

Portrait-drawing robot

The search of the algorithm that—starting from a picture—is able to detect the most important lines of the face has been particularly long and difficult. I used the OpenCV open-source libraries for computer vision and image processing, which are very powerful, but hard to handle. Installing the libraries is not a simple undertaking and using them is even more complicated. I used the OpenCV for Processing. Processing is an open-source programming language and integrated development environment (IDE) built for the electronic arts, new media art, and visual design communities with the purpose of teaching the fundamentals of computer programming in a visual context.

The algorithm initially found facial lines using the algorithms for calculation of edges of a picture. So I used the Canny edge detector, the Sobel edge detector, and all the other main edge detection algorithms, but none of these proved to be adequate to draw a face. Then I changed the course and used the Laplacian filter with threshold. I think I reached a good result because it takes less than 10 minutes to draw a portrait, which enables me to take pictures of people and make their portrait before they lose their patience.

CIRCUIT CELLAR: What new technologies excite you and why?

ALESSANDRO: I work almost strictly with Arduino microcontrollers. I was excited with the arrival of Linux-embedded mini-PCs (e.g., the Raspberry PI, the pcDuino, and BeagleBoard.org’s BeagleBone Black). Forcibly, I’m very intrigued by the new Arduino Tre, which is a mini-PC with Linux joined with an Arduino Leonardo. Combining a PC’s processing power of with Linux with the real-time management of the sensors and actuators made by an Arduino is an interesting road. It offers the possibility to manage the real-time processing of video streams through, for example, the OpenCV libraries, with the option of acquiring signals from analog sensors and the possibility of drive motors. For example, this enables one to have a completely autonomous 3-D printer and to perform the slicing and management of the 3-D printer. It also opens up new perspectives in the robotics and computer vision. The main limitation, which is now present in embedded systems, is the limited processing capacity. The ability to have in the same card a Linux system—with the world of applications and drivers already available—linked to the ability to manage physical devices brings a revolution. And I’m already excited to see the next results.

Read the complete interview in Circuit Cellar 292 November 2014.

Single-Board, Arduino Uno Shield-Compatible Dev Kit

Nordic Semiconductor’s new Arduino Uno shield-compatible nRF51 DK development kit supports Bluetooth Smart, ANT, and 2.4-GHz designs. Nordic also announced the availability of its nRF51 Dongle, which is a 16 mm × 28 mm USB dongle for the testing, analysis, and development of Bluetooth Smart, ANT, and 2.4-GHz applications.Nordic-nRF51 DK_1

The nRF51 DK is based on Nordic’s nRF51 Series SoC, which combines a 2.4-GHz multiprotocol radio, 32-bit ARM Corte M0 processor, flash memory, and 16- or 32-KB RAM. The SoCs can support a wide range of peripherals and are available in quad flat no-lead (QFN) and wafer level chip scale package (WLCSP) options.

Key points about the nRF51 DK and nRF51 Dongle

  • You can use the nRF51 DK with a variety of third-party Arduino shield expansion boards. It also supports ARM mbed for rapid prototyping projects.
  • The nRF51 DK allows access to all device peripherals, interfaces, and I/Os.
  • The nRF51 DK includes four user-programmable buttons and LEDS plus voltage and current pins to measure device power consumption.
  • nRF51 DK and nRF51 Dongle are supported by standard tool-chain options including Keil, IAR, and Gnu Compiler Collection (GCC).
  • The 63 mm × 101 mm nRF51 DK includes a coin-cell battery holder for field testing
  • You can use nRF51 DKhe DK as a programmer for other target boards that use the nRF51 Series SoC.

The nRF51 DK costs $69. The nRF51 Dongle is $49.

Source: Nordic Semiconductor

Arduino-Based Tube Stereo Preamp Project

If you happen to be electrical engineer as well as an audiophile, you’re in luck. With an Arduino, some typical components, and a little knowhow, you can build DIY tube stereo preamplifier design.

Shannon Parks—owner of Mahomet, IL-based Parks Audio—designed his “Budgie” preamp after reading an article about Arduino while he was thinking about refurbishing a classic Dynaco PAS-3.

Budgie preamp (Source: S. Parks)

Budgie preamp (Source: S. Parks)

In a recent audioXpress article about the project, Parks noted:

Over the last 10 years, I have built many tube power amplifiers but I had never built a tube preamplifier. The source switching seemed particularly daunting. A friend recommended that I refurbish a classic Dynaco PAS-3 which has been a popular choice with many upgrade kit suppliers. Unfortunately, the main part of these older designs is a clumsy rotary selector switch, not to mention the noisy potentiometers and slide switches. In the 1980s, commercial stereo preamplifiers started using IC microcontrollers that permitted cleaner designs with push-button control, relays for signal switching, and a wireless remote. While reading an article about the Arduino last year, I realized these modern features could easily be incorporated into a DIY preamplifier design.

All the circuits are on one custom PCB along with the power supply and microcontroller (Source: S. Parks)

All the circuits are on one custom PCB along with the power supply and microcontroller (Source: S. Parks)

Parks said the Arduino made sense for a few key reasons:

I found these features were incredibly useful:

  • A bank of relays could switch between the four stereo inputs as well as control mute, standby, gain, and bass boost settings.
  • A red power LED could use PWM to indicate if the preamplifier is muted or in standby.
  • An IR receiver with a remote could control a motor-driven volume potentiometer, change the source input selection, and turn the unit on/off. Any IR remote could be used with a code learning mode.
  • A backlit display could easily show all the settings at a glance.
  • Momentary push buttons could select the input device, bass boost, gain, and mute settings.
  • Instead of using several Arduino shields wired to an Arduino board, all the circuits could fit on one custom PCB along with the power supply and the microcontroller.

Parks used an Arduino Nano, which 0.73” × 1.70”. “The tiny Nano can be embedded using a 32-pin dual in-line package (DIP) socket, which cleans up the design. It can be programmed in-circuit and be removed and easily replaced,” he noted.

Parks used an Arduino Nano for the preamp project (Source: S. Parks)

Parks used an Arduino Nano for the preamp project (Source: S. Parks)

Parks described the shift register circuit:

The Budgie preamplifier uses a serial-in, parallel-out (SIPO) shift register to drive a bank of relays ….

A SIPO shift register is used to drive a bank of relays (Source: S. Parks)

A SIPO shift register is used to drive a bank of relays (Source: S. Parks)

Only four Arduino digital outputs—enable, clock, latch, and data—are needed to control eight DPDT relays. These correspond to the four outputs labeled D3, D4, D5, and D7 s …. The Texas Instruments TPIC6C595 shift register used in this project has heavy-duty field-effect transistor (FET) outputs that can handle voltages higher than logic levels. This is necessary for operating the 24-V relays. It also acts as a protective buffer between the Arduino and the relays.

Here you see the how to set up the Arduino Nano, LCD, power supply, push button , IR and motor control circuits (Source: S. Parks)

Here you see the how to set up the Arduino Nano, LCD, power supply, push button , IR and motor control circuits (Source: S. Parks)

As for the audio circuit, Parks explained:

The 12B4 triode was originally designed to be used in televisions as a vertical deflection amplifier. New-old-stock (NOS) 12B4s still exist. They can be purchased from most US tube resellers. However, a European equivalent doesn’t exist. The 12B4 works well in preamplifiers as a one-tube solution, having both high input impedance and low output impedance, without need for an output transformer. An audio circuit can then be distilled down to a simple circuit with few parts consisting of a volume potentiometer and a grounded cathode gain stage.
The 12B4 has about 23-dB gain, which is more than is needed. This extra gain is used as feedback to the grid, in what is often referred to as an anode follower circuit. The noise, distortion, and output impedance are reduced (see Figure 3). Using relays controlled by the Arduino enables switching between two feedback amounts for adjustable gain. For this preamplifier, I chose 0- and 6-dB overall gain. A second relay enables a bass boost with a series capacitor.
You only need a lightweight 15-to-20-V plate voltage to operate the 12B4s at 5 mA. Linearity is very good due to the small signal levels involved, as rarely will the output be greater than 2 VPP. A constant current source (CCS) active load is used with the 12B4s instead of a traditional plate resistor. This maximizes the possible output voltage swing before clipping. For example, a 12B4 biased at 5-mA plate current with a 20-kΩ plate resistor would drop 100 V and would then require a 120-V supply voltage or higher. Conversely, the CCS will only drop about 2 V. Its naturally high impedance also improves the tube’s gain and linearity while providing high levels of power supply noise rejection.

This article first appeared in Circuit Cellar’s sister publication, audioXpress (July 2014).

 

 

DIY Arduino-Based ECG System

Cornell University students Sean Hubber and Crystal Lu built an Arduino-based electrocardiography (ECG) system that enables them to view a heart’s waveform on a mini TV. The basic idea is straightforward: an Arduino Due converts a heartbeat waveform to an NTSC signal.

Here you can see the system in action. The top line (green) has a 1-s time base. The bottom line (yellow) has a 5-s time base. (Source: Hubber & Lu)

Here you can see the system in action. The top line (green) has a 1-s time base. The bottom line (yellow) has a 5-s
time base. (Source: Hubber & Lu)

In their article, “Hands-On Electrocardiography,” Hubber and Lu write:

We used the Arduino Due to convert the heartbeat waveform to an NTSC signal that could be used by a mini-TV. The Arduino Due continuously sampled the input provided by the voltage limiter at 240 sps. Similar to MATLAB, the vectorized signal was shifted left to make room at the end for the most recent sample. This provided a continuous real-time display of the incoming signal. Each frame outputted to the mini-TV contains two waveforms. One has a 1-s screen width and the other has a 5-s screen width. This enables the user to see a standard version (5 s) and a more zoomed in version (1 s). Each frame also contains an integer representing the program’s elapsed time. This code was produced by Cornell University professor Bruce Land.

As you can see in the nearby block diagram, Hubber and Lu’s ECG system comprises a circuit, an Arduino board, a TV display, MATLAB programming language, and a voltage limiter.

The system's block diagram (Circuit Cellar 289, 2014)

The system’s block diagram (Circuit Cellar 289, 2014)

The system’s main circuit is “separated into several stages to ensure that retrieving the signal would be user-safe and that sufficient amplification could be made to produce a readable ECG signal,” Hubber and Lu noted.

The first stage is the conditioning stage, which ensures user safety through DC isolation by initially connecting the dry electrode signals directly to capacitors and resistors. The capacitors help with DC isolation and provide a DC offset correction while the resistors limit the current passing through. This input-conditioning stage is followed by amplification and filtering that yields an output with a high signal-to-noise ratio (SNR). After the circuit block, the signal is used by MATLAB and voltage limiter blocks. Directly after DC isolation, the signal is sent into a Texas Instruments INA116 differential amplifier and, with a 1-kΩ RG value, an initial gain of 51 is obtained. The INA116 has a low bias current, which permits the high-impedance signal source. The differential amplifier also utilizes a feedback loop, which prevents it from saturating.

Following the differentiation stage, the signal is passed through multiple filters and receives additional amplification. The first is a low-pass filter with an approximately 16-Hz cutoff frequency. This filter is primarily used to eliminate 60-Hz noise. The second filter is a high-pass filter with an approximately 0.5-Hz cutoff frequency. This filter is mostly used to eliminate DC offset. The total amplification at this stage is 10. Since the noise was significantly reduced and the SNR was large, this amplification produced a very strong and clear signal. With these stages done, the signal was then strong enough to be digitally analyzed. The signal could then travel to both the MATLAB and voltage limiter blocks.

Hubber and Lu’s article was published in Circuit Cellar 289, 2014. Get it now!