The Future of Data Acquisition Technology

Maurizio Di Paolo Emilio

Maurizio Di Paolo Emilio

By Maurizio Di Paolo Emilio

Data acquisition is a necessity, which is why data acquisition systems and software applications are essential tools in a variety of fields. For instance, research scientists rely on data acquisition tools for testing and measuring their laboratory-based projects. Therefore, as a data acquisition system designer, you must have an in-depth understanding of each part of the systems and programs you create.

I mainly design data acquisition software for physics-related experiments and industrial applications. Today’s complicated physics experiments require highly complex data acquisition systems and software that are capable of managing large amounts of information. Many of the systems require high-speed connections and digital recording. And they must be reconfigurable. Signals that are hard to characterize and analyze with a real-time display are evaluated in terms of high frequencies, large dynamic range, and gradual changes.

Data acquisition software is typically available in a text-based user interface (TUI) that comprises an ASCII configuration file and a graphic user interface (GUI), which are generally available with any web browser. Both interfaces enable data acquisition system management and customization, and you don’t need to recompile the sources. This means even inexperienced programmers can have full acquisition control.

Well-designed data acquisition and control software should be able to quickly recover from instrumentation failures and power outages without losing any data. Data acquisition software must provide a high-level language for algorithm design. Moreover, it requires data-archiving capability for verifying data integrity.

You have many data acquisition software options. An example is programmable software that uses a language such as C. Other software and data acquisition software packages enable you to design the custom instrumentation suited for specific applications (e.g., National Instruments’s LabVIEW and MathWorks’s MATLAB).

In addition to data acquisition software design, I’ve also been developing embedded data acquisition systems with open-source software to manage user-developed applications. The idea is to have credit-card-sized embedded data acquisition systems managing industrial systems using open-source software written in C. I’m using an ARM processor that will give me the ability to add small boards for specific applications (e.g., a board to manage data transmission via Wi-Fi or GSM).

A data acquisition system’s complexity tends to increase with the number of physical properties it must measure. Resolution and accuracy requirements also affect a system’s complexity. To eliminate cabling and provide for more modularity, you can combine data acquisition capabilities and signal conditioning in one device.

Recent developments in the field of fiber-optic communications have shown longer data acquisition transmission distances can cause errors. Electrical isolation is also an important topic. The goal is to eliminate ground loops (common problems with single-ended measurements) in terms of accuracy and protection from voltage spikes.

During the last year, some new technological developments have proven beneficial to the overall efficacy of data acquisition applications. For instance, advances in USB technology have made data acquisition and storage simpler and more efficient than ever (think “plug and play”). Advances in wireless technology have also made data transmission faster and more secure. This means improved data acquisition system and software technologies will also figure prominently in smartphone design and usage.

If you look to the future, consumer demand for mobile computing systems will only increase, and this will require tablet computers to feature improved data acquisition and storage capabilities. Having the ability to transmit, receive, and store larger amounts of data with tablets will become increasingly important to consumers as time goes on. There are three main things to consider when creating a data acquisition-related application for a tablet. Hardware connectivity: Tablets have few control options (e.g., Wi-Fi and Bluetooth). Program language support: Many tablets support Android apps created in Java. Device driver availability: Device drivers permit a high-level mode to easily and reliably execute a data acquisition board’s functionality. C and LabVIEW are not supported by Android or Apple’s iOS. USB, a common DAQ bus, is available in a set of tablets. In the other case, an adapter is required. In these instances, moving a possible data acquisition system to a tablet requires extra attention.

For all of the aforementioned reasons, I think field-programmable arrays (FPGAs) will figure prominently in the evolution of data acquisition system technology. The flexibility of FPGAs makes them ideal for custom data acquisition systems and embedded applications.

Microcontroller-Based Heating System Monitor

Checking a heating system’s consumption is simple enough.

Heating system monitor

Determining a heating system’s output can be much more difficult, unless you have this nifty design. This Atmel ATmega microcontroller-based project enables you to measure heat output as well as control a circulation pump.

Heating bills often present unpleasant surprises. Despite your best efforts to economise on heating, they list tidy sums for electricity or gas consumption. In this article we describe a relatively easy way to check these values and monitor your consumption almost continuously. All you need in order to determine how much heat your system delivers is four temperature sensors, a bit of wiring, and a microcontroller. There’s no need to delve into the electrical or hydraulic components of your system or modify any of them.

A bit of theory
As many readers probably remember from their physics lessons, it’s easy to calculate the amount of heat transferred to a medium such as water. It is given by the product of the temperature change ΔT, the volume V of the medium, and the specific heat capacity CV of the medium. The power P, which is amount of energy transferred per unit time, is:

P= ΔT × CV × V // Δt

With a fluid medium, the term V // Δt can be interpreted as a volumetric flow Vt. This value can be calculated directly from the flow velocity v of the medium and the inner diameter r of the pipe. In a central heating system, the temperature difference ΔT is simply the difference between the supply (S) and return (R) temperatures. This yields the formula:

P = (TS – TR) × CV × v × pr2

The temperatures can easily be measured with suitable sensors. Flow transducers are available for measuring the flow velocity, but installing a flow transducer always requires drilling a hole in a pipe or opening up the piping to insert a fitting.

Measuring principle
Here we used a different method to determine the flow velocity. We make use of the fact that the supply and return temperatures always vary by at least one to two degrees due to the operation of the control system. If pairs of temperature sensors separated by a few metres are mounted on the supply and return lines, the flow velocity can be determined from the time offset of the variations measured by the two sensors…

As the water flows through the pipe with a speed of only a few metres per second, the temperature at sensor position S2 rises somewhat later than the temperature at sensor position S, which is closer to the boiler.

An ATmega microcontroller constantly acquires temperature data from the two sensors. The time delay between the signals from a pair of sensors is determined by a correlation algorithm in the signal processing software, which shifts the signal waveforms from the two supply line sensors relative to each other until they virtually overlap.The temperature signals from the sensors on the return line are correlated in the same manner, and ideally the time offsets obtained for the supply and return lines should be the same.

To increase the sensitivity of the system, the return line sensor signals are applied to the inputs of a differential amplifier, and the resulting difference signal is amplified. This difference signal is also logged as a function of time. The area under the curve of the difference signal is a measure of the time offset of the temperature variations…

Hot water please
If the heating system is also used to supply hot water for domestic use, additional pipes are used for this purpose. For this reason, the PCB designed by the author includes inputs for additional temperature sensors. It also has a switched output for driving a relay that can control a circulation pump.

Under certain conditions, controlling the circulation pump can save you a lot of money and significantly reduce CO2 emissions. This is because some systems have constant hot water circulation so users can draw hot water from the tap immediately. This costs electricity to power the pump, and energy is also lost through the pipe walls. This can be remedied by the author’s circuit, which switches on the circulation pump for only a short time after the hot water tap is opened. This is detected by the temperature difference between the hot water and cold water supply lines…

Circuit description
The easiest way to understand the schematic diagram is to follow the signal path. It starts at the temperature sensors connected to the circuit board, which are NTC silicon devices.

Heating system monitor schematic

Their resistance varies by around 0.7–0.8% per degree K change in temperature. For example, the resistance of a KT110 sensor is approximately 1.7 kΩ at 5 °C and approximately 2.8 kΩ at 70 °C.

The sensor for supply temperature S forms a voltage divider with resistor R37. This is followed by a simple low-pass filter formed by R36 and C20, which filters out induced AC hum. U4a amplifies the sensor signal by a factor of approximately 8. The TL2264 used here is a rail-to-rail opamp, so the output voltage can assume almost any value within the supply voltage range. This increases the absolute measurement accuracy, since the full output signal amplitude is used. U4a naturally needs a reference voltage on its inverting input. This is provided by the combination of R20, R26 and R27. U5b acts as an impedance converter to minimise the load on the voltage divider…

Thermal power

PC connection
The circuit does not have its own display unit, but instead delivers its readings to a PC via an RS485 bus. Its functions can also be controlled from the PC. IC U8 looks after signal level conversion between the TTL transmit and receive lines of the ATmega microcontroller’s integrated UART and the differential RS485 bus. As the bus protocol allows several connected (peer) devices to transmit data on the bus, transmit mode must be selected actively via pin 3. Jumper JP3 must be fitted if the circuit is connected to the end of the RS485 bus. This causes the bus to be terminated in 120 Ω, which matches the characteristic impedance of a twisted-pair line…

[Via Elektor-Projects.com]

Q&A: Chris Paiano (Problem Solving & Design)

Chris Paiano is an Elko, NV-based problem engineer. His father introduced him to programming at an early age, and Chris has continued to team with his father to write software and firmware for some of his hardware designs. Chris has written dozens of unique application notes for the Cypress Semiconductor Programmable-System-on-Chip (PSoC) chipset. He is currently using PSoC in an innovative household project and dreams of finishing his concept for environmentally friendly electric/hybrid vehicle wheeldrive retrofit kits.

Chris Paiano working with his “office assistants” (bearded dragons)

You can read the complete interview in Circuit Cellar 272 March 2013.

NAN PRICE: Tell us a little about your background.

CHRIS PAIANO: I went to school in Orlando, FL, all the way through college at the University of Central Florida, where I obtained my bachelor’s degree in Computer Engineering.

I started at a very young age. My father always had an electronics workbench and I spent time there when I could. When I was 2 years old, he brought me home an Apple ][ with some floppy disks and told me there were games to be played—if I could only figure out how to make them work.

The Apple ][ was not the most user-friendly or intuitive computer system, by any means. In order to accomplish my important goal of playing video games, I had to learn how to work with the computer’s clunky command-line interface (CLI). Once I figured out how to make all the games work, I wanted to fully automate them so I didn’t have to go through all the manual steps to play them every time (also, so my friends could start them up without me). So, I spent much time developing automatic start-up scripts, from the Applesoft HELLO program to MS-DOS configuration start-up menus, supporting whatever memory management method was required to play certain games, along with icon-driven pre-Windows menu systems that made these early systems usable by my friends, family, and clients.

This evolved into more elaborate scripting and programming to fill the gaps where the tools I needed did not exist, so I had to create them. My possibilities really opened up when I began developing firmware to complement my father’s hardware designs.

NAN: Tell us about your company, Christopher Paiano Engineering (CpE).

CHRIS: I design and program prototypes for various clients. I provide them with ideas at various development stages, which I turn into something that they can mass produce. I’ve just redesigned my website (www.cpeproto.com), by the way. It has a sleeker, simple interface and is easier to navigate now. No more Java menu with annoying sound effects!

NAN: Several of your projects are built around the Cypress Semiconductor programmable system-on-chip (PSoC). Is that your go-to chipset?

CHRIS: Yes, mainly because of how versatile and capable it is. It seems to be sufficient to take care of most any embedded task or set of tasks that come to mind.

For example, recently, the proprietor of a local game/tech/arcade business approached me to build a custom, inexpensive door chime. He wanted customers to hear random, recognizable portal sounds from popular video games whenever customers entered or exited his shop.

I started with an inexpensive motion sensor product from a local superstore. I added a Cypress CY8C27443 PSoC, as I have several lying around for general projects. I made a copy of my “Playing WAV Files with a PSoC” app note project to modify.

I added code to randomly cycle through available sound clips in the memory and I was able to provide 1.9805 s of audio at 8 kHz with the 16 KB of RAM available in this chip. The client was happy with this. He settled on two portal sounds (from The Legend of Zelda and Super Mario Brothers) and the chime has been in use for several months now. Customer feedback has been excellent. Everyone entering the place immediately recognizes the sounds and loves it!

NAN: You’ve written more than 30 application notes for the Cypress chipset, including PongSoC and the Video RTA. Can you explain the process?

CHRIS: Sometimes Cypress would post bounties for app notes that they’d like to see written on a certain topic or capability. Other times, I’d have an interesting personal project for which I decided to utilize a PSoC. I would then decide it might make a good app note, so I’d write it up and submit it. Either way, I’d usually develop the project side-by-side with my father. (We make an excellent hardware/software team.) I work out whatever firmware and PC/smartphone apps may be necessary, and he builds the PSoC circuit board with which to test. Then, I document it all, arrange it, and edit it into an app note (or, in some cases, an article).

Sometimes a project is just too complex to squeeze into a single PSoC’s resources and the simplest solution is to just add another PSoC. Communication between PSoCs can be quick and easy to implement, so distributing tasks and maintaining synchronization is not too difficult. This was the solution for the video real-time analyzer (RTA) app note where, realistically, there were only enough internal analog resources to provide three filters in each PSoC. With the Video RTA, one just adds as many PSoCs to the bus as is necessary to achieve the desired analyzer resolution.

The PongSoC was a fun one! Once I learned it was possible to combine some internal PSoC modules and algorithms to generate a stable composite video signal, I immediately decided I wanted to try and utilize this new capability to recreate a Pong-like embedded game-on-a-chip. I could already generate sound effects and read potentiometers for paddle inputs, I just needed to work it all out. I had a great time doing so, testing it with friends and playing with the variables to tweak the gameplay, and so forth.

Additionally, all 40 of my PSoC application notes are now available in some capacity on my updated website, as Cypress does not actively market the older PSoC families that many of my projects utilized in the past. I get enough e-mail requests for source code and documentation from this collection, so I have just gone ahead and taken the time to restore as many as I could find from my archives to the new website.

NAN: Your two-part article series “PSoC Design Techniques” describes how to build an eight-channel mixer and how DSP effects and a user interface can be added to it (Circuit Cellar 216–217, 2008). Describe the design and why you chose this design concept.

CHRIS: This was a great challenge. In a chip that traditionally would only allow for four full audio pathways in the provided analog resources (four PGA modules utilizing the normal I/O paths provided by PSoC Designer), we managed to figure out a way to utilize the remaining switched-capacitor blocks to act as signal mixers and gain stages with enough live reconfigurable resources to add potentiometers to control volume for each channel. Since there was still plenty of code space, I went ahead and added some DSP effects (reverb and pitch shift) along with a voice menu and flash-settings memory.

I really wanted to showcase what efficient design and algorithms could accomplish in a single piece of silicon, and I’m quite pleased with the way this project turned out. I still use the resulting device on my workbench and in my setups. It comes in handy sometimes. I have not updated it at all. I’ve been using it as is and it is still available for purchase on my website for anyone interested in experimenting with one.

NAN: Are you currently working on or planning any microprocessor-based projects?

CHRIS: Currently, I’m working on a PSoC solution for my broken dishwasher.

Chris Paiano is developing a PSoC solution for a broken dishwasher. In addition to the fix, he plans to make it smartphone-controllable.

The control module on this appliance has failed, so I am wiring it into a PSoC to make it work again as well as add some new capabilities (such as keeping a wash/rinse/door open log so it can tell when the dishes contained within it are clean or dirty, and adding a Bluetooth module so I can check the status and control/program the appliance from my smartphone).

This is the type of personal project I like to work on in my free time. It also might make a good app note or article in the future, as it involves an Android application and Bluetooth communication. It also increases my capabilities, if I have to figure out anything new. And that is always good.

I am almost ready to hook it up to the dishwasher, let it try running through the cycles, and hope I don’t flood my house in the process. Ah, the pure excitement of engineering!

The entire interview is available in Circuit Cellar 272 March 2013.

Free Raspberry Pi Poster

The Raspberry Pi is a computer with no casing, no keyboard, no hard disk and no screen. Despite all that, it’s taking the world by storm!

Get your free Raspberry Pi poster now, courtesy of Elektor, RS Components, and CC! Go ahead: download, print, and then enjoy!

Free Raspberry Pi Poster

RASPBERRY PI ESSENTIALS

Model A has 256-MB RAM, one USB port, and no Ethernet port (network connection). Model B has 512-MB RAM, two USB ports, and an Ethernet port.

The Raspberry Pi Model B, revision 2 board:

  • Status led labels: top led has label “ACT” and bottom led has label “100”
  • Header P2 is not populated
  • The text underneath the Raspberry Pi logo reads: “(C) 2011,12”
  • The area next to the micro usb port has CE and FCC logos and the text “Made in China or UK” along the board edge.
  • There are two 2.9-mm holes in the PCB, which can be used as mounting holes.
  • P5 is a new GPIO header with four additional GPIO pins and four power pins. Also note that some pin and I2C port numbers of connector P1 have been modified between revisions!
  • Header P6 (left from the HDMI port) was added, short these two pins to reset the computer or wake it up when powered down with the “sudo halt” command.

The Raspberry Pi measures 85.60 mm × 56 mm × 21 mm, with a little overlap for the SD card and connectors which project over the edges. It weighs 45 g.

The SoC is a Broadcom BCM2835. This contains an ARM ARM1176JZFS, with floating point, running at 700 MHz, and a Videocore 4 GPU. The GPU is capable of BluRay quality playback, using H.264 at 40 Mbps. It has a fast 3D core which can be accessed using the supplied OpenGL ES2.0 and OpenVG libraries.

The Raspberry Pi is capable of using hardware acceleration for MPEG-2 and VC-1 playback, but you’ll need to buy license keys at the Raspberry Pi Store to unlock this functionality.

Which programming languages can you use? Python, C/C++, Perl, Java, PHP/MySQL, Scratch, and many more that can run under Linux.

TROUBLESHOOTING TIPS

If you’re getting a flashing red PWR LED or random restarts during the booting process, it’s likely that your PSU or USB cable has problems. The Raspberry Pi is pretty picky and requires a solid 5-V/1000-mA power supply. For other issues and more troubleshooting tips check out the extensive overview at the eLinux website

Circuitcellar.com is an Elektor International Media website.

Member Profile: Chris Coulston

Chris Coulston

Location: Erie, PA

Education: BA, Physics (Slippery Rock University), BS and MS, Computer Engineering (Penn State University), and PhD, Computer Science (Penn State University)

Occupation: Computer Engineering Professor, Penn State University

Member Status: Chris started reading Circuit Cellar 10 years ago, when he became a professor and wanted to learn more about embedded and mixed-signal systems. He says much of what he teaches has been gleaned from Circuit Cellar. He often has students from his embedded systems class read articles because it [provides] “invaluable insight into the practice of embedded systems design from working professionals in the field.”

Technical Interests: Chris says his career in academia has enabled him to study a range of fascinating subjects in areas as diverse as theoretical computer science to embedded systems design. He has worked on creating a neural network that mimics the neural function behind swimming and locomotion behaviors in the leech hirudo medicinalis, optimizing Steiner minimal trees, and recently designing embedded systems that leverage the photoelectric effect of LEDs to make them behave as sensors.

Most Recent Embedded Tech-Related Acquisition: To keep his embedded systems class current, Chris experiments with new technologies every year. This year, Chris says his students will interface a Microchip Technology PIC18F26K22 to a Raspberry Pi. “I am enjoying the broad support base of the Raspberry Pi and the excellent development tools provided by Microchip,” Chris said.

Current Projects: Chris is working on getting the Raspberry Pi to “play nice” with the PIC18F26K22 before making it a class assignment. Recently, he has also been working on replicating Jeff Han’s LED matrix multitouch display. “This is a neat project where Jeff took an off-the-shelf LED matrix and enabled it to sense where a user was touching the display. Hopefully you’ll see my version of this concept in these pages,” Chris said.

Thoughts on the Future of Embedded Technology: Chris thinks the industry will continue its trend of peripheral integration (hopefully) with an eye on simplifying the task of laying out PBCs. He notes that crossbar switches between microcontroller subsystems and the I/O pins enable cleaner and quicker PCB layouts and integration of new subsystems (e.g., DACs) reduces chip count and layout effort.