The IAR Connect Portal for the IoT

IAR Systems recently launched IAR Connect, which is a portal that presents product development platforms and serves as hub intended to connect innovators interested in the Internet of Things (IoT) and other emerging technologies.IAR Systems connect

One of the first members of IAR Connect is Renesas Electronics. Customers using the Renesas Synergy Platform can begin product development at a high level of abstraction and focus completely on designing innovative features for embedded applications and connected devices.

“The best way to take advantage of the possibilities of the new connected world is by providing new technology offerings, sharing knowledge and establishing strategic alliances, such as our strong partnership with Renesas. With IAR Connect, we enable innovation by connecting people and technologies. I invite everyone to connect, get inspired and explore the potential of the Internet of Things and the connected world at”, said IAR Systems CEO Stefan Skarin in a released statement.

Source: IAR Systems

New 16- and 32-Mb Advanced Low-Power SRAMs

Renesas Electronics recently introduced two new Advanced Low Power SRAMs with more than 500 times the resistance to soft errors compared to full CMOS memory cells. Fabricated using the 110-nm process, the new RMLV1616A Series of 16-Mb devices and the RMWV3216A Series of 32-Mb devices feature an innovative memory cell technology that improves reliability and leads to longer battery life.

The Advanced LP SRAM devices feature their memory cell technology that delivers soft error resistance over 500 times that of conventional full CMOS memory cells. Thus, it’s an intelligent solution for use in measurement devices, smart grid-related devices, and industrial equipment.

Features and specs:

  • Advanced LP SRAM technology for improved soft error resistance and enhanced reliability
  • Reduction of standby current tfor longer backup battery service life. Low current consumption levels are less than half the levels of comparable earlier Renesas SRAM products
  • The 16-Mb RMLV1616A Series is available in three packages: 48-ball FBGA, 48-pin TSOP, and 52-pin µTSOP
  • The 32-Mb RMWV3216A Series is available in a 48-ball FBGA package.

Samples of the RMLV1616A Series and RMWV3216A Series will be available in September. The 16-Mb RMLV1616A Series costs $16.50 per unit. The 32-Mb RMWV3216A Series is priced at $31 per unit. Mass production is scheduled to begin in October 2015.

Source: Renesas Electronics Corp.

Microcontroller-Based Air Quality Mapper

Raul Alvarez Torrico’s Air Quality Mapper is a portable device designed to track levels of CO2 and CO gasses for constructing “Smog Maps” to determine the healthiest routes. Featuring a Renesas RDKRL78G13 development board, the Mapper receives location data from its GPS module, takes readings of the CO2 and CO concentrations along a specific route, and stores the data in an SD card. With the aid of PC utility software, you can upload the data to a web server and see maps of gas concentrations in a web browser.

air q

The portable data logger prototype

In his Circuit Cellar 293 article (December 2014), Torrico notes:

My design, the Air Quality Mapper, is a data-logging, online visualization system comprising a portable data logger and a webserver for the purpose of measuring and visualizing readings of the quality of air in given areas. You take readings over a given route and then upload the data to the server, which in turn serves a webpage containing a graphical representation of all readings using Google Maps technology.

The webpage displaying CO2 measurements acquired in a session

The webpage displaying CO2 measurements acquired in a session

The data logging system features a few key components: a Renesas YRDKRL78G13 development board,  a Polstar PMB-648 GPS module, an SD card, and gas sensors.

The portable data logger hardware prototype is based on the Renesas YRDKRL78G13 development board, which contains a Renesas R5F100LEA 16-bit microcontroller with 64 KB of program memory, 4 KB of data flash memory, and 4 KB of RAM, running from a 12-MHz external crystal…

Air Quality Mapper system

Air Quality Mapper system

The board itself is a bit large for a portable or hand-held device (5,100 x 5,100 mils); but on the other hand, it includes the four basic peripherals I needed for the prototype: a graphic LCD, an SD card slot, six LEDs, and three push buttons for the user interface. The board also includes other elements that could become very handy when developing an improved version of the portable device: a three-axis accelerometer, a temperature sensor, ambient light sensor, a 512-KB serial EEPROM, a small audio speaker, and various connection headers (not to mention other peripherals less appealing for this project: an audio mic, infrared emitter and detector, a FET, and a TRIAC, among other things). The board includes a Renesas USB debugger, which makes it a great entry-level prototyping board for Renesas RL78/G13 microcontrollers.

For the GPS module, I used a Polstar PMB-648 with 20 parallel satellite-tracking channels. It’s advertised as a low-power device with built-in rechargeable battery for backup memory and RTC backup. It supports the NMEA0183 v2.2 data protocol, it includes a serial port interface, and it has a position accuracy 2DRMS of approximately 5 m and velocity accuracy of 0.1 m per second without selective availability imposed. It has an acquisition time of 42 s from a cold start and 1 s from a hot start. It also includes a built-in patch antenna and a 3.3- to 5-V power supply input.

The GPS module provides NMEA0183 V2.2 GGA, GSV, GSA, and RMC formatted data streams via its UART port. A stream comes out every second containing, among other things, latitude, longitude, a timestamp, and date information. In the system, this module connects to the R5F100LEA microcontroller’s UART0 port at 38,400 bps and sources the 3.3-VDC power from the YRDKRL78G13 board.

For the CO2 sensor, I used a Hanwei Electronics Co. MG-811 sensor, which has an electrolyte that in the presence of heat reacts in proportion to the CO2 concentration present in air. The sensor has an internal heating element that needs to be powered with 6 VDC or 6 VAC. For small CO2 concentrations, the sensor outputs a higher voltage, and for high concentrations the output voltage decreases. Because I didn’t have proper calibration instrumentation at hand for this type of sensor, I made a very simple calibration process just by exposing the sensor to a “clean air” environment outside the city. I took an average of various readings in a 15-minute period to define a 400-PPM concentration, which is generally defined as the average for a clean air environment. Not an optimal calibration method of course, but I thought it was acceptable to get some meaningful data for prototyping purposes. For a proper calibration of the sensor, I would’ve needed another CO2 sensing system already calibrated with a high degree of accuracy and a set up in a controllable environment (e.g., a laboratory) in order to generate and measure the amount of CO2.

This sensor provides an output voltage between 30 and 50 mV. And due to their high output impedance, the signal must be properly conditioned with an op-amp. So, I used a Microchip Technology MCP6022 instrumentation amplifier in a noninverting configuration with a gain of 9.2.

You can read the complete article in Circuit Cellar 293 (December 2014).

New 40-nm Microcontrollers for Motor Control

Renesas Electronics Corp. recently announced the RH850/C1x series of 32-bit microcontrollers (MCUs), which it said are designed for motor control in hybrid electric vehicles (HEVs) and electric vehicles (EVs). Based on Renesas’s 40-nm process, the RH850/C1x series features the RH850/C1H and RH850/C1M MCUs, which enable embedded designers to enhance efficiency, reduce system costs, and achieve higher safety levels for HEV/EV motor control systems.

Source: Renesas Electronics Corp.

Source: Renesas Electronics Corp.

The new RH850/C1x devices can be used with the RAA270000KFT RH850 family power supply management IC (PMIC), which is currently available in sample quantities. The power management IC integrates into one device all the power supply systems required for MCU operation, two external sensor power supply tracks, and a full complement of monitoring and diagnostic functions, significantly reducing the user burden associated with power supply system design.

The RH850/C1H and RH850/C1M MCUs incorporate large memory capacities achieved through 40 nm MONOS process technology. The RH850/C1x series is based on Renesas’s metal oxide nitride oxide silicon (MONOS) embedded flash, which has an extensive track record in mass production. The MONOS characteristics include fast readout, low power consumption, and large storage capacity. The RH850/C1M and RH850/C1H devices offer memory capacities of 2 MB and 4 MB, respectively. In addition, 32-KB data flash memory, with essentially the same functionality as EEPROM, is included for data storage.

The microcontrollers also feature an extensive set of peripheral functions for HEV/EV motor control. The RH850/C1x MCUs can implement three types of motor control in hardware: sine wave PWM, over modulation, and square wave.

Samples of the RH850/C1H and RH850/C1M MCUs are scheduled to be available from the beginning of 2015 and will cost $45 and $50 per unit, respectively. Mass production is scheduled for May 2016 and is expected to reach a scale of 100,000 units per month.

Source: Renesas Electronics Corp.

The Sun Chaser Energy-Harvesting System

When Sjoerd Brandsma entered the 2012 Renesas Green Energy Challenge, he wanted to create a fun project that would take advantage of his experience at a company that heavily uses GPS.

Brandsma, who lives in Kerkwijk, The Netherlands, has worked as a software engineer and is currently an R&D manager at CycloMedia, which produces 360° street-level panoramic images with geographic information system (GIS) accuracy.

Ultimately, Brandsma’s Sun Chaser project won third prize in the Renesas Green Energy Challenge. The Sun Chaser is an energy-harvesting system that automatically orients a solar panel to face the sun.

Photo 1: The Sun Chaser’s stepper motor controls the solar panel‘s “tilting.”

Photo 1: The Sun Chaser’s stepper motor controls the solar panel‘s “tilting.”

“The Sun Chaser perfectly follows the sun’s path and keeps the battery fully charged when there’s enough sunlight,” Brandsma says in his article about the project, which appears in Circuit Cellar’s June issue. ”It can power a small electronics system as long as there’s enough sunlight and no rain, which would damage the system due to lack of protection. This project also demonstrates that it’s possible to build an interesting green-energy system with a tight budget and a limited knowledge of  electronics.”

A registered GPS calculates the orientation of the Sun Chaser’s solar panel, which is mounted on a rotating disc. “You can use an external compass, the internal accelerometer, a DC motor, and a stepper motor to determine the solar panel’s exact position,” Brandsma says. “The Sun Chaser uses Renesas Electronics’s RDKRL78G13 evaluation board running the Micriµm µC/OS-III real-time kernel.”

The following article excerpt describes the GPS reference station and evaluation board in greater detail. The issue with Brandsma’s full article is available online for membership download or single-issue purchase.

Whenever you want to know where you are, you can use a GPS receiver that provides your position. A single GPS receiver can provide about 10 to 15 m (i.e., 33’ to 50’) position accuracy. While this is sufficient for many people, some applications require positioning with significantly higher accuracy. In fact, GPS can readily produce positions that are accurate to 1 m (3’), 0.5 m (18”), or even 1 to 2 cm (less than 1“). A technique called “differential GPS” can be used to achieve higher accuracy.

The differential technique requires one GPS receiver to be located at a known position (often called a control or reference point) and a second “rover” receiver at the location to be measured. The information from the two GPS receivers (rover and control) is combined to determine the rover’s position. That’s where a GPS reference station comes in. It functions as the control point and serves potentially unlimited users and applications. Leica Geosystems has published an excellent introductory guide about GPS reference stations (Refer to the Resources at the end of this article.)

The GPS reference station should always be located at a position with a broad sight. In some situations it can be difficult to provide a decent power supply to the system. When regular power isn’t available, a solar panel can power the GPS reference station.

My Sun Chaser GPS reference station uses a 10-W solar panel connected to a 12-V battery to provide enough power. To increase the energy harvesting, the solar panel is mounted on a rotating disc that can be controlled by a DC motor to point in the desired direction. A stepper motor controls the solar panel’s “tilting.” Photo 1 highlights the main components.

The RDKRL78G13 is an evaluation and demonstration tool for Renesas Electronics’s RL78 low-power microcontrollers. A set of human-machine interfaces (HMIs) is tightly integrated with the RL78’s features. I used several of these interfaces to control other devices, read sensors, or store data.

Most of the system’s hardware is related to placing the solar panel in the correct position. Figure 1 shows the top-level components used to store the GPS information and position the solar panel.

Figure 1: The Sun Chaser’s components include a Renesas Electronics RDKRL78G13 evaluation board, a GPS receiver, a stepper motor, and an SD card.

Figure 1: The Sun Chaser’s components include a Renesas Electronics RDKRL78G13 evaluation board, a GPS receiver, a stepper motor, and an SD card.

The RDKRL78G13 evaluation board has an on-board temperature and light sensor. Both sensor values are stored on the SD card. The on-board light sensor is used to determine if rotating/tilting makes sense (at night it’s better to sleep). For this project, the temperature values are stored just for fun so I could make some graphs or do some weather analysis.

A micro-SD memory card slot on the RDKRL78G13 evaluation board provides file system data storage. I used it to store all incoming data and log messages using the FAT16/FAT32 file system.

The on-board Renesas Electronics RQK0609CQDQS MOSFET controls the DC motor that rotates the evaluation board. The DC motor can be controlled by applying a PWM signal generated from one of the RL78’s timers. The MOSFET is controlled by the RL78’s TO05 port and powered from the 12-V battery. A PWM signal is generated on TO05 by using Timer4 as a master and Timer5 as a slave. It’s only necessary to rotate clockwise, so additional hardware to rotate the platform counterclockwise is not required.

A digital compass is needed to determine the evaluation board’s rotated position or heading (see Figure 2). The Honeywell HMC5883L is a widely used and low-cost compass. This I2C-based compass has three-axis magnetoresistive sensors and a 12-bit ADC on board. It can read out values at a 160-Hz rate, which is more than enough for this project.

Figure 2: A Honeywell HMC5883L digital compass verifies the evaluation board’s rotated position or heading.

Figure 2: A Honeywell HMC5883L digital compass verifies the evaluation board’s rotated position or heading.

The compass uses the RL78’s IICA0 port through the Total Phase Beagle debug header, which is mounted on the RDKRL78G13 evaluation board. The Beagle analyzer provides easy access to this I2C port, which increases the flexibility to change things during prototyping.

The HMC5883L compass turned out to be a very sensitive device. Even the slightest change in the hardware setup seemed to influence the results when rotating. This meant some sort of calibration was needed to ensure the output was consistent every time the system started. [Brandsman’s full article descibes how how the HMC5883L can be calibrated. It’s important to know that every time the system starts, it makes a full turn to calibrate the compass.

A GPS module must be connected to the system to provide the system’s current location. I wanted the GPS module to be inexpensive, 3.3-V based, and have an easy and accessible interface (e.g., UART).

Figure 3 shows a schematic of a Skylab M&C Technology SKM53 GPS module, which is based on the MediaTek 3329 GPS receiver module. This module supports NMEA messages and the MTK NMEA Packet Protocol interface to control things such as power saving, output message frequency, and differential global positioning system (DGPS).

Unfortunately, the 3329 receiver can’t output “raw” GPS data (e.g., pseudorange, integrated carrier phase, Doppler shift, and satellite ephemeris), which would significantly improve the GPS reference station’s capabilities. Due to budget and time limitations (it takes some more software development effort to handle this raw data), I didn’t use a receiver that could output raw GPS data.

Figure 3:A Skylab M&C Technology SKM53 GPS receiver obtains the system’s current location.

Figure 3:A Skylab M&C Technology SKM53 GPS receiver obtains the system’s current location.

The SKM53 GPS receiver is connected to the RL78’s UART2. All data from the GPS receiver is stored on the SD card. As soon as a valid GPS position is received, the system calculates the sun’s position and moves the platform into the most ideal position.

A compact stepper motor is needed to tilt the platform in very small steps. The platform had to be tilted from fully vertical to fully horizontal in approximately 6 h when the sun was exactly following the equator, so speed wasn’t really an issue. I wanted to do very fine tilting, so I also needed a set of gears to slow down the platform tilting.

I used an inexpensive, easy-to-use, generic 5-V 28BYJ-48 stepper motor (see Figure 4). According to the specifications, the 28BYJ-48 stepper motor has a 1/64 gear reduction ratio and 64 steps per rotation (5.625°/step) of its internal motor shaft.

An important consideration here is that you don’t want to retain power on the stepper motor to keep it in position. This particular stepper motor has some internal gears that prevent the platform from flipping back when the stepper motor is not powered.

The stepper motor can be controlled by the well-known ULN2003 high-voltage high-current Darlington transistor array. The ULN2003 is connected to P71-P74. Each of the ULN2003’s four outputs is connected to one of the stepper motor’s coils. When two neighbor coils are set high (e.g., P72 and P73), the stepper motor will step in that direction.

When it comes to solar panels, you can build your own panel out of individual solar cells or buy a fully assembled one with known specifications. I used a no-name 10-W solar panel. The size (337 mm long × 205 mm wide × 18 mm high) was acceptable and it delivered more than enough energy. I used a charge controller to protect the battery from overcharging and to prevent it from supplying power to the solar panel at night.

Like solar panels, many charge controllers and battery protectors can be used in such a system. I chose the lazy approach: Just take one off the shelf. The CMP12/24 charge controller is specially designed for small solar systems. It has a stabilized 12-V output, which is taken from the connected battery. It can handle up to 12 A of charging or load current and, according to the specifications, it consumes about 20 mA of quiescent current. There is some room for improvement, but it worked for my project.

I had some 7805 voltage regulators lying around, which I figured could do the job and supply just enough power when the system was starting up. However, when it comes to power saving, the 7805 is not the way to go. It’s a linear regulator that works by taking the difference between the input and output voltages and burning it up as wasted heat.

What I needed was a switching regulator or a buck converter. I used a National Semiconductor (now Texas Instruments) LM2596. Note: The LM2596 is made by several companies and is available in inexpensive, high-quality modules (most cost a little more than $1 per converter). These ready-to-use modules already have the necessary capacitors, diodes, and so forth on board, so it’s really a matter of plug and play.

I used a lead acid RT1219 12-V 1.9-AH battery for power storage. You can use any 12-V battery with sufficient capacity.

Editor’s Note: Check out other projects from the 2012 Renesas RL78 Green Energy Challenge.

MCU-Based Experimental Glider with GPS Receiver

When Jens Altenburg found a design for a compass-controlled glider in a 1930s paperback, he was inspired to make his own self-controlled model aircraft (see Photo 1)

Photo 1: This is the cover of an old paperback with the description of the compass-controlled glider. The model aircraft had a so-called “canard” configuration―a very modern design concept. Some highly sophisticated fighter planes are based on the same principle. (Photo used with permission of Ravensburger.)

Photo 1: This is the cover of an old paperback with the description of the compass-controlled glider. The model aircraft had a so-called “canard” configuration―a very modern design concept. Some highly sophisticated fighter planes are based on the same principle. (Photo used with permission of Ravensburger.)

His excellent article about his high-altitude, low-cost (HALO) experimental glider appears in Circuit Cellar’s April issue. The MCU-based glider includes a micro-GPs receiver and sensors and can climb to a preprogrammed altitude and find its way back home to a given coordinate.

Altenburg, a professor at the University of Applied Sciences Bingen in Germany, added more than a few twists to the 80-year-old plan. An essential design tool was the Reflex-XTR flight simulation software he used to trim his 3-D glider plan and conduct simulated flights.

Jens also researched other early autopilots, including the one used by the Fiesler Fi 103R German V-1 flying bomb. Known as buzz bombs during World War II, these rough predecessors of the cruise missile were launched against London after D-Day. Fortunately, they were vulnerable to anti-aircraft fire, but their autopilots were nonetheless mechanical engineering masterpieces (see Figure 1)

“Equipped with a compass, a single-axis gyro, and a barometric pressure sensor, the Fiesler Fi 103R German V-1 flying bomb flew without additional control,” Altenburg says. “The compass monitored the flying direction in general, the barometer controlled the altitude, and the gyro responded to short-duration disturbances (e.g., wind gusts).”

Figure 1: These are the main components of the Fieseler Fi 103R German V-1 flying bomb. The flight controller was designed as a mechanical computer with a magnetic compass and barometric pressure sensor for input. Short-time disturbances were damped with the main gyro (gimbal mounted) and two auxiliary gyros (fixed in one axis). The “mechanical” computer was pneumatically powered. The propeller log on top of the bomb measured the distance to the target.

Figure 1: These are the main components of the Fieseler Fi 103R German V-1 flying bomb. The flight controller was designed as a mechanical computer with a magnetic compass and barometric pressure sensor for input. Short-time disturbances were damped with the main gyro (gimbal mounted) and two auxiliary gyros (fixed in one axis). The “mechanical” computer was pneumatically powered. The propeller log on top of the bomb measured the distance to the target.

Altenburg adapted some of the V-1’s ideas into the flight control system for his 21st century autopilot glider. “All the Fi 103R board system’s electromechanical components received an electronic counterpart,” he says. “I replaced the mechanical gyros, the barometer, and the magnetic compass with MEMS. But it’s 2014, so I extended the electronics with a telemetry system and a GPS sensor.” (See Figure 2)

Figure 2: This is the flight controller’s block structure. The main function blocks are GPS, CPU, and power. GPS data is processed as a control signal for the servomotor.

Figure 2: This is the flight controller’s block structure. The main function blocks are GPS, CPU, and power. GPS data is processed as a control signal for the servomotor.

His article includes a detailed description of his glider’s flight-controller hardware, including the following:

Highly sophisticated electronics are always more sensitive to noise, power loss, and so forth. As discussed in the first sections of this article, a glider can be controlled by only a magnetic compass, some coils, and a battery. What else had to be done?

I divided the electronic system into different boards. The main board contains only the CPU and the GPS sensor. I thought that would be sufficient for basic functions. The magnetic and pressure sensor can be connected in case of extra missions. The telemetry unit is also a separate PCB.

Figure 3 shows the main board. Power is provided by a CR2032 lithium coin-cell battery. Two low-dropout linear regulators support the hardware with 1.8 and 2.7 V. The 1.8-V line is only for the GPS sensor. The second power supply provides the CPU with a stable voltage. The 2.7 V is the lowest voltage for the CPU’s internal ADC.

It is extremely important for the entire system to save power. Consequently, the servomotor has a separate power switch (Q1). As long as rudder movement isn’t necessary, the servomotor is powered off. The servomotor’s gear has enough drag to hold the rudder position without electrical power. The servomotor’s control signal is exactly the same as usually needed. It has a 1.1-to-2.1-ms pulse time range with about a 20-ms period. Two connectors (JP9 and JP10) are available for the extension boards (compass and telemetry)..

I used an STMicroelectronics LSM303DLM, which is a sensor module with a three-axis magnetometer and three-axis accelerometer. The sensor is connected by an I2C bus. The Bosch Sensortec BMP085 pressure sensor uses the same bus.

For telemetry, I applied an AXSEM AX5043 IC, which is a complete, narrow-band transceiver for multiple standards. The IC has an excellent link budget, which is the difference between output power in Transmit mode and input sensitivity in Receive mode. The higher the budget, the longer the transmission distance.

The AX5043 is also optimized for battery-powered applications. For modest demands, a standard crystal (X1, 16-MHz) is used for clock generation. In case of higher requirements, a temperature-compensated crystal oscillator (TCXO) is recommended.

The main board’s hardware with a CPU and a GPS sensor is shown. A CR2032 lithium coin-cell battery supplies the power. Two regulators provide 1.8  and 2.7 V for the GPS and the CPU. The main outputs are the servomotor’s signal and power switch.

Figure 3: The main board’s hardware with a CPU and a GPS sensor is shown. A CR2032 lithium coin-cell battery supplies the power. Two regulators provide 1.8 and 2.7 V for the GPS and the CPU. The main outputs are the servomotor’s signal and power switch.

Altenburg’s article also walks readers through the mathematical calculations needed to provide longitude, latitude, and course data to support navigation and the CPU’s most important sensor— the u-blox Fastrax UC430 GPS. He also discusses his experience using the Renesas Electronics R5F100AA microcontroller to equip the prototype board. (Altenburg’s glider won honorable mention in the 2012 Renesas RL78 Green Energy Challenge, see Photos 2 and 3).

The full article is in the April issue, now available for download by members or single-issue purchase.

One of the final steps is mounting the servomotor for rudder control. Thin cords connect the servomotor horn and the rudder. Two metal springs balance mechanical tolerances.

Photo 2: One of the final steps is mounting the servomotor for rudder control. Thin cords connect the servomotor horn and the rudder. Two metal springs balance mechanical tolerances.

Photo 2: This is the well-equipped high-altitude low-cost (HALO) experimental glider.

Photo 3: This is the well-equipped high-altitude low-cost (HALO) experimental glider.

Q&A: Scott Potter (Engineering a Way To Clean Solar Mirrors)

Designer and technology executive Scott Potter won first prize in the 2012 RL78 Green Energy Challenge, presented by Renesas Electronics in partnership with Circuit Cellar and Elektor magazines. The global contest called on participants to develop green energy designs utilizing Renesas’s RL78 microcontrollers. Scott won with his solar-powered electrostatic cleaning robot, which removes dust and debris from the tracking mirrors of large-scale concentrating solar power plants.—Mary Wilson, Managing Editor

Scott Potter

MARY: Where do you live and what is your current occupation?

SCOTT: I live in Los Gatos, CA, and I’m a senior director at Jasper Wireless, a company providing machine-to-machine (M2M) data communications services. I have been with Jasper since the beginning in 2005 when the company started with four people and a plan. Now Jasper is approaching 150 employees and we are a global company. I have served many roles at Jasper, working on location technology, device middleware, back-end reporting, and front-end software.

My other job is as an inventor at Taft Instruments. We are just now forming around the technology I developed for the RL78 design challenge. We are finding there is a big need for this solution in the solar industry, which is poised for tremendous growth in the next few years.

MARY: How did you first become interested in embedded electrical design? What is your educational background?

SCOTT: I started working for my father at his startup in the basement of our home in Long Island when I was a teenager (child labor laws were more lax back then). We were doing embedded electronics design along with mechanical modeling and prototyping. I learned from the best and it has stuck with me all these years. I went on to get a BSEE from Tufts University and I toyed with the idea of business school, but it never gripped me like engineering.

MARY: Why did you enter the 2012 Renesas RL78 Green Energy Challenge? What about its focus appealed to you?

SCOTT: The green energy design challenge came along at the perfect time. I had been working on the cleaning robot for a few months when I saw the challenge. The microcontroller I had originally picked was turning out to be not a great choice, and the challenge made me take a look at the RL78. The part was perfect, and the challenge gave me a goal to work toward.

MARY: How did the idea of designing a robot to clean solar-tracking mirrors (i.e., heliostats) for solar power plants come to you?

SCOTT: I can’t say it came to me all at once. I have participated in solar technology development sporadically throughout my career, and I have always tried to stay abreast of the latest developments. After the lessons learned from the parabolic trough concentrators, the move to high-concentration concentrating solar power (CSP) plants, which more efficiently convert solar power to electrical power, struck me as the right thing to do.

The high-concentration CSP plant utilizes hundreds of thousands of mirrors spread over many acres. The mirrors reflect sunlight onto a centrally located tower, which creates intense heat that drives a steam turbine generator.

The efficiency gains from the higher temperatures will make this the dominant technology for utility scale power generation. But there is a high maintenance cost associated with all of those mirror surfaces, especially in environments where water is scarce. A number of people have realized this and proposed various solutions to keeping the surfaces clean. Unfortunately, none of the proposed solutions will work well at the scale of a large utility plant.

I experimented with quite a few waterless cleaning techniques before coming back to electrostatics. It was my wife, Dia, who reminded me that NASA had been cleaning dust off panels on space missions for years using electrostatic principles. She convinced me to stop working with the forced-air concept I was doing at the time and switch to electrostatics. It was definitely the right choice.

MARY: What does the system do? What problems does it solve for power plants? How is the device different from what is already available for the task of cleaning heliostats?

SCOTT: Our patent-pending device is unique in many ways. It is completely autonomous, requiring no external power or water. The installation time is less than 10 s per heliostat, after which the device will remain attached and operating maintenance free for the life of the plant. We borrowed a marketing term from the military for this: “Set it and forget it.”

Most of the competing products have a long installation time and require some external wiring and maintenance. These can be logistical problems in a field of hundreds of thousands of mirrors.

Our device is also unique in that it cleans continuously. This prevents accumulation of organic materials on the surface, which can mix with dew and make a bio-film on the surface. That film bakes on and requires vigorous scrubbing to remove. We also have a feature to handle the dew, or frost, if it’s present.

MARY: What were some of your design challenges along the way and how did you address them?

SCOTT: They were numerous. The first challenge was the power source. It is important that this device be entirely self-powered to avoid having to install any wiring. I had to find a solar-panel configuration that provided enough power at the right voltage levels. I started with lower voltages and had a lot of trouble with the boost converters.

I also couldn’t use any battery storage because of the life requirement. This means that everything has to operate intermittently, gracefully shutting down when the sun fades and then coming up where it left off when the sun returns.

The next challenge was the mechanical drive. This had to grip the mirror tightly enough to resist a stream of water from a cleaning hose (infrequent cleaning with water will probably still be performed). And it had to do this with no power applied.

Another big challenge was the high-voltage electronics. It turns out there is little off-the-shelf technology available for the kind of high-voltage circuitry I needed. Large line output power transformers (LOPTs) for old cathode ray tubes (CRTs) are too large and expensive.

Some of the resonant high-voltage circuits used for cold cathode fluorescent lighting (CCFL) can be used as building blocks, but I had to come up with quite a few innovations to be able to control this voltage to perform the cleaning task. I had more than a few scorched breadboards before arriving at the current design, which is very small, light, and powerful.

MARY: You recently formed Taft Instruments (click here for Taft website). Who are the players in the company and what services does it provide?

SCOTT: We formed Taft instruments to commercialize this cleaning technology. We have been very fortunate to attract a very talented team that has made tremendous progress promoting the company in industry and attracting investment.

We have Steve Gluck and Gary Valinoti, both highly respected Wall Street executives who have galvanized the company and provided opportunities I could never have imagined. They are now recruiting the rest of the team and we are talking to some extremely qualified people. And of course my wife, Dia, is making numerous contributions that she will probably never get credit for.

MARY: How’s business? How would you describe the market for your product and the potential for growth and reach (both domestically and globally)?

SCOTT: We are not at the commercial deployment stage just yet. Our immediate focus is on the field trials we are starting with a number of industry players and the US Department of Energy National Laboratories. We fully expect the trials to be successful and for our large-scale rollouts to begin in about a year.

The market potential for this is tremendous. I’m not sure anyone fully realizes yet the global transformation that is about to take place. Now that the “grid parity” point is near (the point where the cost of solar power is competitive with fossil fuels), solar will become one of the fastest-growing markets we have seen in a century.

Entire national energy pictures will change from single-digit percentages to being dominated by solar. It is a very exciting time in the solar industry, and we are very happy to be part of it.

MARY: Are you individually—or is your company—developing any new designs? If so, can you tell us something about them?

SCOTT: Yes. I can’t say much, but we are working on some very interesting new technologies that will improve on the electrostatic cleaning principles. This technology will vastly expand the base that we can work with.

MARY: You describe yourself as a “serial entrepreneur” with a strong technical background in electronics, software, hardware, and systems design. That combination of skills comes in handy when establishing a new business. But it also helped you land your day job eight years ago as Director of Location Technology at Jasper Wireless. What do you see as future key trends in M2M communications?

SCOTT: M2M has really taken off since we began in 2005. Back then, there were only a few applications people had envisioned taking wireless. That list has exploded, and some analysts are predicting volumes of M2M endpoints that exceed the human population by tenfold!

We have seen large growth in a number of different verticals over the years, the most apparent one right now being automotive, with all the car companies providing connected services. Jasper is uniquely positioned to offer a global solution to these companies through our carrier partners.

MARY: Over the years, you have gained expertise in areas ranging from embedded electronics and wireless, to applications of the global positioning and geographic information systems (GPS and GIS). What do you enjoy most and what are some career highlights? Is one your involvement in the development of a GPS for the New York fire department’s recovery operations after the collapse of the World Trade Center?

SCOTT: What I enjoy most is working with motivated teams to create compelling products and services. One of my proudest moments was when our team at Links Point rose to the 9/11 challenge. At the time, I was a founder and the chief technology officer of Links Point, which provided GPS and location mapping.

When the request came from the New York fire department for a solution to locating remains at the recovery site, the team dedicated themselves to providing a solution no first responder had ever had access to previously. And we did that in record time. We had to come up with a proposal in a half-day and implement it within three days. You have to realize that GPS and PDAs were very new at the time and there were a lot of technical challenges. We also had to compete with some other companies that were proposing more accurate surveying equipment, such as laser ranging.

Our product, a PDA with a GPS attachment, won out in the end. The advantages of our handheld devices were that they were rugged and that firefighters could easily carry them into Ground Zero. We got the opportunity and honor of serving the  FDNY because of the extreme talent, dedication, and professionalism of my team. I would like to mention them: Jerry Kochman, Bill Campbell, Murray Levine, Dave Mooney, and Lucas Hjelle.

MARY: What is the most important piece of advice you would give to someone trying to make a marketable product of his or her design for an electrical device?

SCOTT: Whatever the device, make sure you are passionate about it and committed to seeing it come through. There is a quote that Dia framed for me hanging in my lab—this is attributed to Goethe, but there is some question about that. Anyway, the quote is very inspirational:

“Until one is committed, there is hesitancy, the chance to draw back. Concerning all acts of initiative (and creation), there is one elementary truth that ignorance of which kills countless ideas and splendid plans: that the moment one definitely commits oneself, then Providence moves too. All sorts of things occur to help one that would never otherwise have occurred. A whole stream of events issues from the decision, raising in one’s favor all manner of unforeseen incidents and meetings and material assistance, which no man could have dreamed would have come his way. Whatever you can do, or dream you can do, begin it. Boldness has genius, power, and magic in it. Begin it now.” I

Editor’s note: For more details, schematics, and a video of Scott Potter’s solar-powered electrostatic cleaning robot, click here.

RL78 Challenge Winner’s Workspace in Lewisville, TX

Lewisville, TX-based electrical engineer Michael Hamilton has been a busy man. During the past 10 years, he created two companies: A&D Technologies, which supplies wireless temperature and humidity controllers, and Point & Track, which provides data-gathering apps and other business intelligence tools. And in his spare time, he designed a cloud electrofusion machine for welding 0.5″ to 2″ polyethylene fittings. It  won Second Prize in the 2012 Renesas RL78 Green Energy Challenge.

In an interview slated for publication in Circuit Cellar 273 (April 2013), Hamilton describes some of his projects, shares details about his first microcontroller design, and more.

Michael Hamilton in his workspace. Check out the CNC machine and 3-D printer.

During the interview process, he also provided a details about his workspace, in which he has a variety of interesting tools ranging from a CNC machine to a MakerBot 3-D printer. Hamilton said:

I have a three-axis CNC machine and MakerBot 3-D printer. I use the CNC machine to cut out enclosures and the 3-D printer to create bezels for LCDs and also to create 3-D prototypes. These machines are extremely useful if you need to make any precise cuts or if you want to create 3-D models of future products.

Hamilton also noted:

I recently purchased a Rigol Technologies DSA-815-TG spectrum analyzer. This device is a must-have, right behind the oscilloscope. It enables you to see all the noise/interference present in a PCB design and also test it for EMI issues.

Michael Hamilton’s test bench and DSA815

He has a completely separate area for PCB work.

A separate space for PCB projects

Overall, this is an excellent setup. Hamilton clearly has a nice collection must-have EE tools and test equipment, as well as a handy CNC machine and decent desktop storage system. The separate PCB bench is a great feature that helps keep the space orderly and clean.

As for the 3-D printer, well, it’s awesome.

Design a Low-Power System in 2013

A few months ago, we listed the top design projects from the Renesas RL78 Green Energy Challenge. Today, we’re excited to announce that Circuit Cellar‘s upcoming 25th anniversary issue will include a mini-challenge featuring the RL78. In the issue, you’ll learn about a new opportunity to register for an RL78/G14 demonstration kit that you can use to build a low-power design.

Renesas RL78

The RL78/G14 demonstration kit (RDK) is a handy evaluation tool for the RL78/G14 microcontrollers. Several powerful compilers and sample projects will be offered either free-of-charge (e.g., the GNU compiler) or with a code-size-limited compiler evaluation license (e.g., IAR Systems).  Also featured will be user-friendly GUIs, including the Eclipse-based e2studio.


  • 32-MHz RL78/G14 MCU board with integrated debugger and huge peripheral, including Wi-Fi, E Ink display, matrix LCD, audio ports, IR ports, motor control port, FET and isolated triac interfaces
  •  256-KB On-chip flash
  • USB Debugger cable
  • Four factory demos showcasing local and cloud connectivity through Wi-Fi

The CC25 anniversary issue is now available.

Electrostatic Cleaning Robot Project

How do you clean a clean-energy generating system? With a microcontroller (and a few other parts, of course). An excellent example is US designer Scott Potter’s award-winning, Renesas RL78 microcontroller-based Electrostatic Cleaning Robot system that cleans heliostats (i.e., solar-tracking mirrors) used in solar energy-harvesting systems. Renesas and Circuit Cellar magazine announced this week at DevCon 2012 in Garden Grove, CA, that Potter’s design won First Prize in the RL78 Green Energy Challenge.

This image depicts two Electrostatic Cleaning Robots set up on two heliostats. (Source: S. Potter)

The nearby image depicts two Electrostatic Cleaning Robots set up vertically in order to clean the two heliostats in a horizontal left-to-right (and vice versa) fashion.

The Electrostatic Cleaning Robot in place to clean

Potter’s design can quickly clean heliostats in Concentrating Solar Power (CSP) plants. The heliostats must be clean in order to maximize steam production, which generates power.

The robot cleaner prototype

Built around an RL78 microcontroller, the Electrostatic Cleaning Robot provides a reliable cleaning solution that’s powered entirely by photovoltaic cells. The robot traverses the surface of the mirror and uses a high-voltage AC electric field to sweep away dust and debris.

Parts and circuitry inside the robot cleaner

Object oriented C++ software, developed with the IAR Embedded Workbench and the RL78 Demonstration Kit, controls the device.

IAR Embedded Workbench IDE

The RL78 microcontroller uses the following for system control:

• 20 Digital I/Os used as system control lines

• 1 ADC monitors solar cell voltage

• 1 Interval timer provides controller time tick

• Timer array unit: 4 timers capture the width of sensor pulses

• Watchdog timer for system reliability

• Low voltage detection for reliable operation in intermittent solar conditions

• RTC used in diagnostic logs

• 1 UART used for diagnostics

• Flash memory for storing diagnostic logs

The complete project (description, schematics, diagrams, and code) is now available on the Challenge website.


DIY Green Energy Design Projects

Ready to start a low-power or energy-monitoring microcontroller-based design project? You’re in luck. We’re featuring eight award-winning, green energy-related designs that will help get your creative juices flowing.

The projects listed below placed at the top of Renesas’s RL78 Green Energy Challenge.

Electrostatic Cleaning Robot: Solar tracking mirrors, called heliostats, are an integral part of Concentrating Solar Power (CSP) plants. They must be kept clean to help maximize the production of steam, which generates power. Using an RL78, the innovative Electrostatic Cleaning Robot provides a reliable cleaning solution that’s powered entirely by photovoltaic cells. The robot traverses the surface of the mirror and uses a high voltage AC electric field to sweep away dust and debris.

Parts and circuitry inside the robot cleaner

Cloud Electrofusion Machine: Using approximately 400 times less energy than commercial electrofusion machines, the Cloud Electrofusion Machine is designed for welding 0.5″ to 2″ polyethylene fittings. The RL78-controlled machine is designed to read a barcode on the fitting which determines fusion parameters and traceability. Along with the barcode data, the system logs GPS location to an SD card, if present, and transmits the data for each fusion to a cloud database for tracking purposes and quality control.

Inside the electrofusion machine (Source: M. Hamilton)

The Sun Chaser: A GPS Reference Station: The Sun Chaser is a well-designed, solar-based energy harvesting system that automatically recalculates the direction of a solar panel to ensure it is always facing the sun. Mounted on a rotating disc, the solar panel’s orientation is calculated using the registered GPS position. With an external compass, the internal accelerometer, a DC motor and stepper motor, you can determine the solar panel’s exact position. The system uses the Renesas RDKRL78G13 evaluation board running the Micrium µC/OS-III real-time kernel.

[Video: ]

Water Heater by Solar Concentration: This solar water heater is powered by the RL78 evaluation board and designed to deflect concentrated amounts of sunlight onto a water pipe for continual heating. The deflector, armed with a counterweight for easy tilting, automatically adjusts the angle of reflection for maximum solar energy using the lowest power consumption possible.

RL78-based solar water heater (Source: P. Berquin)

Air Quality Mapper: Want to make sure the air along your daily walking path is clean? The Air Quality Mapper is a portable device designed to track levels of CO2 and CO gasses for constructing “Smog Maps” to determine the healthiest routes. Constructed with an RDKRL78G13, the Mapper receives location data from its GPS module, takes readings of the CO2 and CO concentrations along a specific route and stores the data in an SD card. Using a PC, you can parse the SD card data, plot it, and upload it automatically to an online MySQL database that presents the data in a Google map.

Air quality mapper design (Source: R. Alvarez Torrico)

Wireless Remote Solar-Powered “Meteo Sensor”: You can easily measure meteorological parameters with the “Meteo Sensor.” The RL78 MCU-based design takes cyclical measurements of temperature, humidity, atmospheric pressure, and supply voltage, and shares them using digital radio transceivers. Receivers are configured for listening of incoming data on the same radio channel. It simplifies the way weather data is gathered and eases construction of local measurement networks while being optimized for low energy usage and long battery life.

The design takes cyclical measurements of temperature, humidity, atmospheric pressure, and supply voltage, and shares them using digital radio transceivers. (Source: G. Kaczmarek)

Portable Power Quality Meter: Monitoring electrical usage is becoming increasingly popular in modern homes. The Portable Power Quality Meter uses an RL78 MCU to read power factor, total harmonic distortion, line frequency, voltage, and electrical consumption information and stores the data for analysis.

The portable power quality meter uses an RL78 MCU to read power factor, total harmonic distortion, line frequency, voltage, and electrical consumption information and stores the data for analysis. (Source: A. Barbosa)

High-Altitude Low-Cost Experimental Glider (HALO): The “HALO” experimental glider project consists of three main parts. A weather balloon is the carrier section. A glider (the payload of the balloon) is the return section. A ground base section is used for communication and display telemetry data (not part of the contest project). Using the REFLEX flight simulator for testing, the glider has its own micro-GPS receiver, sensors and low-power MCU unit. It can take off, climb to pre-programmed altitude and return to a given coordinate.

High-altitude low-cost experimental glider (Source: J. Altenburg)

2012 ESC Boston: Tech from Microchip, Fujitsu, & More

The 2012 Embedded Systems Conference in Boston started September 17 and ends today. Here’s a wrap-up of the most interesting news and products.


Microchip Technology announced Monday morning the addition of 15 new USB PIC microcontrollers to its line of full-speed USB 2.0 Device PIC MCUs. In a short presentation, Microchip product marketing manager Wayne Freeman introduced the three new 8-bit, crystal-free USB PIC families.

The PIC16F145x family (three devices) features the Microchip’s lowest-cost MCUs. The devices are available in 14- and 20-pin packages, support full-speed USB communication, don’t require external crystals, include PWM with complement generation, and more. They’re suitable for applications requiring USB connectivity and cap sense capabilities.

Microchip’s three PIC18F2x/4xK50 devices (available in 28- and 40/44-pins) enable “easy migration” from legacy PIC18 USB devices. In addition to 1.8- to 5-V operation, they feature a Charge Time Measurement Unit (CTMU) for cap-touch sensing, which makes them handy for data logging systems for tasks such as temperature and humidity measurement.

The nine devices in the PIC18F97J94 family are available in 64-, 80-, and 100-pin packages. Each device includes a 60 × 8 LCD controller and also integrates a real-time clock/calendar (RTCC) with battery back-up. Systems such as hand-held scanners and home automation panels are excellent candidates for these devices.

Several interesting designs were on display at the Microchip booth.

  • The M2M PICtail module was used in an SMS texting system.

This SMS text messaging system was featured at Microchip’s Machine-to-Machine (M2M) station. The M2M PICtail module (located on the bottom left) costs around $200.

  • Microchip featured its PIC MCU iPod Accessory Kit in glucose meter design. It was one of several healthcare-related systems that exhibitors displayed at the conference.

The interface can be an iPhone, iPad, or iPod Touch.

Visit for more information.


As most of you know, the entry period for the Renesas RL78 Green Energy Challenge ended on August 31 and the judges are now reviewing the entries. Two particular demos on display at the Renesas booth caught my attention.

  • A lemon powering an RL78 L12 MCU:

Lemon power and the RL78

  • An R8C capacitive touch system:

Cap touch technology is on the minds of countless electrical engineers.

Go to


I was pleased to see a reprint of Mark Pedley’s recent Circuit Cellar article, “eCompass” (August 2012), on display at Freescale’s booth. The article covers the topics of building and calibrating a tilt‐compensating electronic compass.

A Circuit Cellar reprint for attendees

Two of the more interesting projects were:

  • An Xtrinsic sensor demo:

Xtrinsic and e-compass

  • A Tower-based medical suitcase, which included a variety of boards: MED-BPM (a dev board for blood pressure monitor applications), MED-EKG (an aux board for EKG and heart rate monitoring applications), and more.

Tower System-based medical suitcase


I stopped by the STMicro booth for a look at the STM32F3DISCOVERY kit, but I quickly became interested in the Dual Interface EEPROM station. It was the smartphone that caught my attention (again). Like other exhibitors, STMicro had a smartphone-related application on hand.

  • The Dual EEPROMs enable you to access memory via either  wired or RF interfaces. Energy harvesting is the new function STMicro is promoting. According to the documentation, “It also features an energy harvesting and RF status function.”

The Dual Interface EEPROM family has an RF and I2C interface

  • According to STMicro’s website, the DATALOG-M24LR-A PCB (the green board, top left) “features an M24LR64-R Dual Interface EEPROM IC connected to an STM8L101K3 8-bit microcontroller through an I2C bus on one side, and to a 20 mm x 40 mm 13.56 MHz etched RF antenna on the other one side. The STM8L101K3 is also interfaced with an STTS75 temperature sensor and a CR2330 coin cell battery.”


I’m glad I spend a few moments at the Fujitsu booth. We rarely see Circuit Cellar authors using Fujitsu parts, so I wanted to see if there was something you’d find intriguing. Perhaps the following images will pique your interest in Fujitsu technologies.

The FM3 family, which features the ARM Cortext-M3 core, is worth checking out. FM3 connectivity demonstration

Connectivity demo

Check out Fujitsu’s System Memory site and document ion to see if its memory products and solutions suit your needs. Access speed comparison: FRAM vs. SRAM vs. EEPROM

Access speed comparison

The ESC conference site has details about the other exhibitors that had booths in the exhibition hall.







Renesas RL78-Based Design Project Opportunities

Did you miss the 1:00 PM EST deadline for the Renesas RL78 Green Energy Challenge? Do you have an unfinished project? No worries! You can still make something of your RL78-related project and the work you’ve put into it! Circuit Cellar and Elektor have several exciting non-contest-related opportunities you’ll find interesting and advantageous!

The Circuit Cellar/Elektor staff wants to know about your work. Even if your project is unfinished, let the staff know what you’re working on and the project’s status. Upload your project or email us your information.

If the staff is interested in your work, an editor will consider approaching you about one or all of the following non-contest-related opportunities:

  • Distinctive Excellence: If the editorial team thinks your project has merit, you might be eligible for “Distinctive Excellence” designation. After past design challenges, Distinctive Excellence recipients added the honor to their resumes, wrote articles about their projects, and gained notoriety in the design community.
  • Print Magazine Opportunities: The editorial team might think your project is worthy of being published in Circuit Cellar or Elektor magazine. Design Challenges and the print magazine are completely separate. If you are offered an opportunity to write an article and it is published, you will paid a standard author honorarium.
  • Opportunities: The Circuit Cellar editorial team will review your submission and consider posting it on to show the world the effort and progress you’ve made. You can post your project info on the site in the spirit of sharing and the furtherance of engineering innovation! Who knows? Readers might provide you with valuable feedback about your unfinished project. Or perhaps you’ll inspire another person to build something of their own! Perhaps your project will catch the eye company looking to learn more about you work!
  • Interview Possibilities: The editorial team might find your approach to design interesting and consider interviewing you for an upcoming issue.
  • Future Design Collaboration: The Elektor Lab builds and tests innovative electronics projects. If your project—whether finished or in progress—interests an Elektor Lab engineer or editor, someone might contact you to discuss development, testing, or even production opportunities.

As you can see, you have some excellent reasons to contact the Circuit Cellar/Elektor staff.

To submit a finished project, an abstract, or simply info about our work, you can still use the Challenge Entry Form. Or, you can simply ZIP your files and email them to the Circuit Cellar Editorial Department. (Write “RL78 Project” and your project’s name or registration number in the email’s subject line.)

RL78 Green Energy Design Challenge Deadline Approaches

Attention engineers, programmers, and electronics enthusiasts! The entry deadline of August 31 for the Renesas RL78 Green Energy Challenge is fast approaching. Here are some tips to keep you on schedule.


The challenge is to design an innovative, energy-efficient application that features the Renesas RL78 MCU, RL78/G13 Renesas Demonstration Kit (RDK), and IAR Toolchain. For information, visit the Eligible Parts page on the design challenge site.

Renesas RDK RL78 board


Once you’re done designing your RL78-based project, you need to gather and order your entry materials: project abstract, complete documentation, and code.

Make sure you register for the challenge to obtain a registration number. Label all of your files and documents with your registration number. Don’t put your name on the files and documents.

Consider organizing all of your entry in a ZIP (or RAR) file. Compressing all of your files into one ZIP will keep your entry organized and easier to submit.


Before you submit your entry, go through the following checklist one last time to ensure you have everything:

• Abstract (a short project description)
• Complete documentation (a detailed project description)
• Block diagram(s)
• Schematic(s)
• Project photograph(s)
• Source code
• Files are properly labeled (your name doesn’t appear in the entry files)

More details are posted on the challenge’s FAQ webpage.


Ready to submit your entry? The preferred submission method is to upload your project files via the RL78 Design Challenge Dropbox.

Or send project files to:

RL78 Green Energy Challenge, Circuit Cellar, 4 Park Street, Vernon, CT 06066, USA

Good luck!

DIY Internet-Enabled Home Control System

Why shell out hundreds or thousands of dollars on various home control systems (HCS) when you have the skills and resources to build your own? You can design and implement sophisticated Internet-enabled systems with free tools and some careful planning.

John Breitenbach did just that. He used a microcontroller, free software, and a cloud-based data platform to construct a remote monitoring system for his home’s water heater. The innovative design can email or text status messages and emergency alerts to a smartphone. You can build a similar system to monitor any number of appliances, rooms, or buildings.

An abridged version of Breitenbach’s article, “Internet-Enabled Home Control” (Circuit Cellar 264, July 2012), appears below. (A link to the entire article and an access password are noted at the end of this post.) Breitenbach writes:

Moving from the Northeast to North Carolina, my wife and I were surprised to find that most homes don’t have basements. In the north, the frost line is 36˝–48 ˝ below the surface. To prevent frost heave, foundations must be dug at least that deep. So, digging down an extra few feet to create a basement makes sense. Because the frost line is only 15 ˝ in the Raleigh area, builders rarely excavate the additional 8’ to create basements.

The lack of basements means builders must find unique locations for a home’s mechanical systems including the furnace, AC unit, and water heater. I was shocked to find that my home’s water heater is located in the attic, right above one of the bedrooms (see Photo 1).

Photo 1: My home’s water heater is located in our attic. (Photo courtesy of Michael Thomas)

During my high school summers I worked for my uncle’s plumbing business (“Breitenbach Plumbing—We’re the Best, Don’t Call the Rest”) and saw firsthand the damage water can do to a home. Water heaters can cause some dramatic end-of-life plumbing failures, dumping 40 or more gallons of water at once followed by the steady flow of the supply line.

Having cleaned up the mess of a failed water heater in my own basement up north, I haven’t had a good night’s sleep since I discovered the water heater in my North Carolina attic. For peace of mind, especially when traveling, I instrumented my attic so I could be notified immediately if water started to leak. My goal was to use a microcontroller so I could receive push notifications via e-mails or text messages. In addition to emergency messages, status messages sent on a regular basis reassure me the system is running. I also wanted to use a web browser to check the current status at any time.


The attic monitor is based on Renesas Electronics’s YRDKRX62N demonstration kit, which features the RX62N 32-bit microcontroller (see Photo 2). Renesas has given away thousands of these boards to promote the RX, and the boards are also widely available through distributors. The YRDK board has a rich feature set including a graphics display, push buttons, and an SD-card slot, plus Ethernet, USB, and serial ports. An Analog Devices ADT7420 digital I2C temperature sensor also enables you to keep an eye on the attic temperature. I plan to use this for a future addition to the project that compares this temperature to the outside air temperature to control an attic fan.

Photo 2: The completed board, which is based on a Renesas Electronics YRDKRX62N demonstration kit. (Photo courtesy of Michael Thomas)


Commercial water-detection sensors are typically made from two exposed conductive surfaces in close proximity to each other on a nonconductive surface. Think of a single-sided PCB with no solder mask and tinned traces (see Photo 3).

Photo 3: A leak sensor (Photo courtesy of Michael Thomas)

These sensors rely on the water conductivity to close the circuit between the two conductors. I chose a sensor based on this type of design for its low cost. But, once I received the sensors, I realized I could have saved myself a few bucks by making my own sensor from a couple of wires or a piece of proto-board.

When standing water on the sensor shorts the two contacts, the resistance across the sensor drops to between 400 kΩ and 600 kΩ. The sensor is used as the bottom resistor in a voltage divider with a 1-MΩ resistor up top. The output of the divider is routed to the 12-bit analog inputs on the RX62N microcontroller. Figure 1 shows the sensor interface circuit. When the voltage read by the analog-to-digital converter (ADC) drops below 2 V, it’s time to start bailing. Two sensors are connected: one in the catch pan under the water heater, and a second one just outside the catch pan to detect failures in the small expansion tank.

Figure 1: The sensor interface to the YRDK RX62N board


One of my project goals was to push notifications to my cell phone because Murphy’s Law says water heaters are likely to fail while you’re away for the weekend. Because I wanted to keep the project costs low, I used my home’s broadband connection as the gateway for the attic monitor. The Renesas RX62N microcontroller includes a 100-Mbps Ethernet controller, so I simply plugged in the cable to connect the board to my home network. The open-source µIP stack supplied by Renesas with the YRDK provides the protocol engine needed to talk to the Internet.

There were a couple of complications with using my home network as the attic monitor’s gateway to the world. It is behind a firewall built into my router and, for security reasons, I don’t want to open up ports to the outside world.

My Internet service provider (ISP) occasionally changes the Internet protocol (IP) address associated with my cable modem. So I would never know what address to point my web browser. I needed a solution that would address both of these problems. Enter Exosite, a company that provides solutions for cloud-based, machine-to-machine (M2M) communications.


Exosite provides a number of software components and services that enable M2M communications via the cloud. This is a different philosophy from supervisory control and data acquisition (SCADA) systems I’ve used in the past. The control systems I’ve worked on over the years typically involve a local host polling the hundreds or thousands of connected sensors and actuators that make up a commercial SCADA system. These systems are generally designed to be monitored locally at a single location. In the case of the attic monitor, my goal was to access a limited number of data points from anywhere, and have the system notify me rather than having to continuously poll. Ideally, I’d only hear from the device when there was a problem.

Exosite is the perfect solution: the company publishes a set of simple application programming interfaces (APIs) using standard web protocols that enable smart devices to push data to their servers in the cloud in real time. Once the data is in the cloud, events, alerts, and scripts can be created to do different things with the data—in my case, to send me an e-mail and SMS text alert if there is anything wrong with my water heater. Connected devices can share data with each other or pull data from public data sources, such as public weather stations. Exosite has an industrial-strength platform for large-scale commercial applications. It provides free access to it for the open-source community. I can create a free account that enables me to connect one or two devices to the Exosite platform.

Embedded devices using Exosite are responsible for pushing data to the server and pulling data from it. Devices use simple HTTP requests to accomplish this. This works great in my home setup because the attic monitor can work through my firewall, even when my Internet provider occasionally changes the IP address of my cable modem. Figure 2 shows the network diagram.

Figure 2: The cloud-based network


Web-based dashboards hosted on Exosite’s servers can be built and configured to show real-time and historical data from connected devices. Controls, such as switches, can be added to the dashboards to push data back down to the device, enabling remote control of embedded devices. Because the user interface is “in the cloud,” there is no need to store all the user interface (UI) widgets and data in the embedded device, which greatly reduces the storage requirements. Photo 4 shows the dashboard for the attic monitor.

Photo 4: Exosite dashboard for the attic monitor

Events and alerts can be added to the dashboard. These are logical evaluations Exosite’s server performs on the incoming data. Events can be triggered based on simple comparisons (e.g., a data value is too high or too low) or complex combinations of a comparison plus a duration (e.g., a data value remains too high for a period of time). Setting up a leak event for one of the sensors is shown in Photo 5.

Photo 5: Creating an event in Exosite

In this case, the event is triggered when the reported ADC voltage is less than 2 V. An event can also be triggered if Exosite doesn’t receive an update from the device for a set period of time. This last feature can be used as a watchdog to ensure the device is still working.

When an event is triggered, an alert can optionally be sent via e-mail. This is the final link that enables an embedded device in my attic to contact me anywhere, anytime, to alert me to a problem. Though I have a smartphone that enables me to access my e-mail account, I can also route the alarm message to my wife’s simpler phone through her cellular provider’s e-mail-to-text-message gateway. Most cellular providers offer this service, which works by sending an e-mail to a special address containing the cell phone number. On the Verizon network, the e-mail address is <yourcellularnumber> Other providers have similar gateways.

The attic monitor periodically sends heartbeat messages to Exosite to let me know it’s still working. It also sends the status of the water sensors and the current temperature in the attic. I can log in to Exosite at any time to see my attic’s real-time status. I have also configured events and alarms that will notify me if a leak is detected or if the temperature gets too hot…

The complete article includes details such about the Internet engine, reading the cloud, tips for updating the design, and more.  You can read the entire article by typing netenabledcontrol to open the password-protected PDF.