High-Accuracy Snow Depth Sensor

MaxbotixMaxBotix Snow Depth Sensors operate in –40Cº to 65Cº temperatures with a 5,000-mm maximum range. The sensors include responsive accurate temperature compensation. They perform well during heavy snowfall conditions and provide continued performance during high-wind conditions.

The sensors feature a 200,000-h mean time before failure (MTBF). Their low-power consumption enables them to operate in battery-based systems for extended periods of time (or solar powered systems indefinitely), which eases maintenance requirements and enables remote installations.

There are six different Snow Depth Sensors available. The sensors are equipped for the following interface controls: Pulse Width, Analog Voltage, and Serial data RS232 (MB7354) or TTL (MB7374).

The Snow Depth Sensors cost $149.99.

MaxBotix, Inc.

Registration Open for Sensors Expo & Conference

Thousands of engineers, scientists, and industry professionals are expected to gather for the 28th Annual Sensors Expo & Conference to assess and discuss the development and deployment of sensors and sensors systems.

The Expo & Conference will take place at The Donald E. Stephens Convention Center in Rosemont, IL, from June 25-June 26, 2014, with pre-conference symposia on June 24. Registration is now open at www.sensorsexpo.com.

This event, exclusively focused on sensor technology, will offer more than 65 technical sessions on the latest solutions to current sensing challenges while exploring the most recent sensing technologies. In addition to two full days of education sessions, attendees can participate in three full-day pre-conference symposia, taking place Tuesday, June 24.  The topics include “Designing MEMS In: How to Engage the Supply Chain,” chaired by Karen Lightman, executive director, MEMS Industry Group; “Energy Harvesting for Powering Wireless Sensors,” chaired by Randy Frank, president, Randy Frank & Associates, Ltd.; and “Making the Internet of Things a Reality: A Toolkit for Designing ‘Smart,’ ” chaired by Will Tu, ARM.

“Our team has been working diligently with our advisory board and partners to develop a stellar program offering nine tracks including Chemical & Gas Sensing, Energy Harvesting for Sensor Applications, Internet of Things, M2M, MEMS, Novel Approaches to Measurement and Detection, Power Management for Sensing Applications, Sensors @ Work, and Wireless, in addition to an expanded trade show floor offering hundreds of top vendors in the industry,” said Wendy Loew, group show director.

Conference program topics include smart power grid monitoring, the future of mobile intelligence with sensor fusion, sensors conditioning, challenges of high temperature sensing, and what you need to know to make your product a success. The Expo Hall provides access to suppliers along with information and education on their sensing products and solutions.

In the Expo Hall, attendees will see the latest sensing technologies and solutions, identify new ways to improve products and expand their functionalities using sensors, and learn about “hot” and cutting-edge technology areas. The Expo Hall will feature exhibitors including Analog Devices, Anaren, GridConnect, Microchip Technology, Mouser Electronics, Parker-Hannifin Corporation, Rowebots, STMicroelectronics, and Wyless.

Solar Array Tracker (Part 1): SunSeeker Hardware

Figure 1: These are the H-bridge motor drivers and sensor input conditioning circuits. Most of the discrete components are required for transient voltage protection from nearby lightning strikes and inductive kickback from the motors.

Figure 1: These are the H-bridge motor drivers and sensor input conditioning circuits. Most of the discrete components are required for transient voltage protection from nearby lightning strikes and inductive kickback from the motors.

Graig Pearen, semi-retired and living in Prince George, BC, Canada, spent his career in the telecommunications industry where he provided equipment maintenance and engineering services. Pearen, who now works part time as a solar energy technician, designed the SunSeeker Solar Array tracker, which won third place in the 2012 DesignSpark chipKit challenge.

He writes about his design, as well as changes he has made in prototypes since his first entry, in Circuit Cellar’s October issue. It is the first part of a two-part series on the SunSeeker, which presents the system’s software and commissioning tests in the final installment.

In the opening of Part 1, Pearen describes his objectives for the solar array tracker:

When I was designing my solar photovoltaic (PV) system, I wanted my array to track the sun in both axes. After looking at the available commercial equipment specifications and designs published online, I decided to design my own array tracker, the SunSeeker (see Photo 1 and Figure 1).

I had wanted to work with a Microchip Technology PIC processor for a while, so this was my opportunity to have some fun. I based my first prototype on a PIC16F870 microcontroller but when the microcontroller maxed out, I switched to its big brother, the PIC16F877. Although both prototypes worked well, I wanted to add more features and

The SunSeeker board, at top, contains all the circuits required to control the solar array’s motion. This board plugs into the Microsoft Technology chipKIT MAX32 processor board. The bottom side of the SunSeeker board (green) with the MAX32 board (red) plugged into it is shown at bottom.

The SunSeeker board, at top, contains all the circuits required to control the solar array’s motion. This board plugs into the Microchip Technology chipKIT MAX32 processor board. The bottom side of the SunSeeker board (green) with the MAX32 board (red) plugged into it is shown at bottom.

capabilities. I particularly wanted to add Ethernet access so I could use my home network to communicate with all my systems. I was considering Microchip’s chipKIT Max32 board for the next prototype when Circuit Cellar’s DesignSpark chipKIT contest was announced.

I knew the contest would be challenging. In addition to learning about a new processor and prototyping hardware, the contest rules required me to learn a new IDE (MPIDE), programming language (C++), schematic capture, and PCB design software (DesignSpark PCB). I also decided to make this my first surface-mount component design.

My objective for the contest was to replicate the functionality of the previous Assembly language software. I wanted the new design to be a test platform to develop new features and tracking algorithms. Over the next two to three years of development and field testing, I plan for it to evolve into a full-featured “bells-and-whistles” solar array tracker. I added a few enhancements as the software evolved, but I will develop most of the additional features later.

The system tracks, monitors, and adjusts solar photovoltaic (PV) arrays based on weather and atmospheric conditions. It compiles statistics on these conditions and communicates with a local server that enables software algorithm refinement. The SunSeeker logs a broad variety of data.

The SunSeeker measures, displays, and records the duration of the daily sunny, hazy, and cloudy periods; the array temperature; the ambient temperature; daily minimum and maximum temperatures; incident light intensity; and the drive motor current. The data log is indexed by the day number (1–366). Index–0 is the annual data and 1–366 store the data for each day of the year. Each record is 18 bytes long for a total of 6,588 bytes per year.

At midnight each day, the daily statistics are recorded and added to the cumulative totals. The data logs can be downloaded in comma-separated values (CSV) format for permanent record keeping and for use in spreadsheet or database programs.

The SunSeeker has two main parts, a control module and a separate light sensor module, plus the temperature and snow sensors.

The control module is mounted behind the array where it is protected from the heat of direct sunlight exposure. The sensor module is potted in clear UV-proof epoxy and mounted a few centimeters away on the edge of, and in the same plane as, the array. To select an appropriate potting compound, I contacted Epoxies, Etc. and asked for a recommendation. Following the company’s advice, I obtained a small quantity of urethane resin (20-2621RCL) and urethane catalyst (20-2621CCL).

When controlling mechanical devices, monitoring for proper operation, and detecting malfunctions it is necessary to prevent hardware damage. For example, if the solar array were to become frozen in place during an ice storm, it would need to be sensed and acted upon. Diagnostic software watches the motors to detect any hardware fault that may occur. Fault detection is accomplished in several ways. The H-bridges have internal fault detection for over temperature, under voltage, and shorted circuit. The current drawn by the motors is monitored for abnormally high or low current and the motor drive assemblies’ pulses are counted to show movement and position.

To read more about the DIY SunSeeker solar array tracker, and Pearen’s plans for further refinements, check out the October issue.


CC278: Battery Basics

Front of a battery analyzer

The University of Washington recently announced its engineers have created a wireless communications system that enables everyday devices to power up and connect to the web without the use of batteries. Instead, such devices would tap the energy available in wireless signals.

According to an August article on the university’s website,  engineers have developed a communication system that takes advantage of what they call  “ambient backscatter,”  the TV and cellular transmissions all around us. You can read more about the breakthrough by checking out the university article.

It will be some time before such an approach becomes commercially viable. In the meantime, we’ll still be relying heavily on batteries. With that in mind, you should check out columnist George Novacek’s article in Circuit Cellar’s September issue. Novacek goes “back to the basics” of batteries in this first installment of a two-part series.

“Battery usage has increased due to the proliferation of mobile and cordless devices,” Novacek says in Part 1. “This article describes battery types generally available in retail stores. I’ll discuss their features, operation, and usages. While many exotic batteries and custom packages are available, this article focuses on standard batteries, which are the type you are most likely to encounter.”

He opens his discussion by distinguishing between batteries vs. cells and describing common battery packages.

“Although we tend to use the words ‘battery’ and ‘cell’ interchangeably, there is a difference,” Novacek says. “Batteries comprise cells (e.g., the well-known 9-V battery contains six 1.5-V cells, while the omnipresent AA ‘battery’ and many others are just single cells). I will use the common terminology, even though it may be at times technically incorrect.

“Batteries store chemical energy. When activated, the chemical process occurring internally converts the chemical into electrical energy. Alessandro Volta, an Italian physicist, is credited with inventing the “voltaic pile” in the early 19th century, although archeological discoveries suggest that some form of an electrical battery was known in ancient Babylon. National Carbon Company, known today as Eveready, began marketing a precursor of the ubiquitous carbon-zinc battery in 1896…

“According to Wikipedia, the most common battery packages available today include AA, AAA, C, D, 9-V pack, and different types of “button cells”. There is also a plethora of custom-made battery packs for power tools, cordless telephones, and so forth. No matter what kind of packaging, the battery principles for the given type remain the same.

“There are two categories of batteries: primary (i.e., single use) and rechargeable. Carbon-zinc is the oldest—and at one point the most common—primary battery. They are available in standard packages and inexpensive. Consequently, carbon-zinc batteries are often included by original equipment manufacturers (OEM) with devices (e.g., TV remote controls, portable radios, etc.). Although they have been improved over the years, some significant shortcomings remain, so I avoid using them.”

Novacek goes on to examine the drawbacks and advantages of carbon-zinc, alkaline, lithium, mercuric-oxide, silver-oxide button cell, lead-acid, nickel-cadmium (NiCad), and nickel-metal hydride (NiMH) batteries.

To learn more about what may be powering your handheld or other device, check out the September issue.

Embedded Sensor Innovation at MIT

During his June 5 keynote address at they 2013 Sensors Expo in Chicago, Joseph Paradiso presented details about some of the innovative embedded sensor-related projects at the MIT Media Lab, where he is the  Director of the Responsive Environments Group. The projects he described ranged from innovative ubiquitous computing installations for monitoring building utilities to a small sensor network that transmits real-time data from a peat bog in rural Massachusetts. Below I detail a few of the projects Paradiso covered in his speech.


Managed by the Responsive Enviroments group, the DoppelLab is a virtual environment that uses Unity 3D to present real-time data from numerous sensors in MIT Media Lab complex.

The MIT Responsive Environments Group’s DoppleLab

Paradiso explained that the system gathers real-time information and presents it via an interactive browser. Users can monitor room temperature, humidity data, RFID badge movement, and even someone’s Tweets has he moves throughout the complex.

Living Observatory

Paradiso demoed the Living Observatory project, which comprises numerous sensor nodes installed in a peat bog near Plymouth, MA. In addition to transmitting audio from the bog, the installation also logs data such as temperature, humidity, light, barometric pressure, and radio signal strength. The data logs are posted on the project site, where you can also listen to the audio transmission.

The Living Observatory (Source: http://tidmarsh.media.mit.edu/)


The GesturesEverywhere project provides a real-time data stream about human activity levels within the MIT Media Lab. It provides the following data and more:

  • Activity Level: you can see the Media Labs activity level over a seven-day period.
  • Presence Data: you can see the location of ID tags as people move in the building

The following video is a tracking demo posted on the project site.

The aforementioned projects are just a few of the many cutting-edge developments at the MIT Media Lab. Paradiso said the projects show how far ubiquitous computing technology has come. And they provide a glimpse into the future. For instance, these technologies lend themselves to a variety of building-, environment-, and comfort-related applications.

“In the early days of ubiquitous computing, it was all healthcare,” Paradiso said. “The next frontier is obviously energy.”