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Microcontroller-Based Wireless Pedometer & Pace Tacker Project

Anyone can easily order a pedometer or GPS sports watch on the Internet. But engineers like challenges, right? With the right parts and a little knowhow, you can engineer your own microcontroller-based wireless Bluetooth pedometer and pace tracker.

In the article, “Run With It” (Circuit Cellar 203, December 2014), Ellen Chuang and Julie Wang explain how they built an Atmel ATmega1284P microcontroller-based wireless pedometer and pace tracker. They wrote:

There’s a simple question most runners, walkers, and joggers ask themselves: How fast am I going? There are various tools for measuring pace, including step counters, GPS units, and smartphone applications. Pedometers are common tools for tracking physical activity. However, pedometers are typically either self-contained units that are out of sight and out of mind or expensive products like the FitBit and Nike+. So, for our culminating design project for Cornell University’s ECE 4760 Microcontrollers course, we decided to create a low-budget wireless pedometer and pace tracker.

The wireless pedometer hardware implementation includes a (a) foot module and a (b) wrist module on the right.

The wireless pedometer includes a foot module (a) and a wrist module (b).

Chuang and Wang’s design is notable because they enabled it with Bluetooth so they could connect it with other Bluetooth devices. In addition, they separated the user interface from the measurement unit.

Our system contains two separate modules: a foot-mounted module that captures acceleration data and a wrist-mounted module with a user interface. The foot module captures your acceleration data, lightly processes it to find values of interest, and sends the data over Bluetooth to the wrist module. The wrist module then further processes the information to determine if a step has occurred. The wrist module also handles user input and displaying information on an LCD.

To use the device, the foot unit is strapped on your lower leg and the wrist unit is either strapped to your wrist or held in your hand. At power-up, the units automatically pair over a Bluetooth link. The wrist unit powers up in Configuration mode, which enables you to use the two push buttons to adjust your stride length and also your desired pace in minutes per mile. You are first prompted for your stride length—the average length of one step—and then the targeted speed in minutes per mile. The Enter button enables you to confirm the parameters, exit Configuration mode, and enter into Pace Display mode. In Pace Display mode, the LCD displays the cumulative number of steps, your calculated pace, and your desired pace. At any point, you can reenter Configuration mode by toggling a switch on the wrist module.

Both modules contain an Atmel ATmega1284P microcontroller and an HC-05 Bluetooth master/slave module.

The foot unit contains a 1.5-g, single-axis Freescale Semiconductor MMA2260D accelerometer orientated with its positive measurement axis pointed away from the center of the Earth. We’ll refer to this direction as the z-axis. The analog data coming from the accelerometer is very noisy. To filter out the excessive noise, the accelerometer data passes through a low-pass filter with a cutoff frequency around 33 Hz using a 10-kΩ resistor and 470-nF capacitor. Human stride frequency typically falls between 185 and 200 strides per minute, or around 3.33 Hz. In order to capture this frequency, as well as higher frequency signals that correspond to other foot movements, we set the low-pass filter’s cutoff frequency to 33 Hertz. Additionally, to fully utilize the internal ADC’s 10-bit range, we dropped the voltage across a 20-kΩ resistor…

This is the foot unit. We used MAX233/RS-232 for debugging purposes and not for the final foot module.

This is the foot unit. We used MAX233/RS-232 for debugging purposes and not for the final foot module.

The wrist unit includes a 16 × 2 LCD a number of user input buttons/switches, status-linked LEDs, and a Bluetooth transceiver (see Figure 2). The three buttons and switch are used in Configuration mode. Additionally, we included the following LEDs: a red LED on the board that toggles every time a step is detected; a yellow LED that toggles every time a packet is received via Bluetooth; and a green “keep alive” LED. The software on the microcontroller manages all of these tasks, which we cover in the next section.

The complete article appears in Circuit Cellar 293 (December 2014).

Microcontroller-Based Control Display Component

Jerry Brown, a California-based aerospace engineer, designed and built (both the hardware and software) an MCU-based computer display component (CDC) for a traffic-monitoring system. The system with the CDC is intended for monitoring and recording the accumulative count, direction of travel, speed, and time of day for vehicles that pass by.

In his November 2014 Circuit Cellar article, “MCU-Based Control Display Component,” Brown explained:

For the past five years, I have been working on an embedded project that you might find interesting. As part of a traffic-monitoring system (TMS) developed by a colleague (a retired aerospace/aeronautical engineer), whereby traffic flow on city streets and boulevards is monitored, I designed and built (both the hardware and software) a dual Microchip Technology PIC18F4520 microcontroller-based control display component (CDC, see Photo 1). My motivation to develop the CDC came about as a result of my chance meeting with my colleague when we were both judges at the local county-wide science fair. He explained the concept of the TMS to me and his motivation for developing it and said he needed an electrical engineer to design and build the CDC. Would I be interested? You bet I was.

Photo 1: Fully functional CDC prototype

Photo 1: Fully functional CDC prototype

Brown went on to describe system.

The TMS comprises a dual laser beam transmitter, a dual sensor receiver, and the CDC (see Figure 1). It is intended for unmanned use on city streets, boulevards, and roadways to monitor and record the cumulative count, direction of travel, speed, and time of day for vehicles that pass by a specific location during a set time period (e.g., 12 to 24 hours).

Figure 1: Traffic Monitoring System showing the Laser Beam Transmitter, the Sensor Receiver and the Control Display Component

Figure 1: Traffic Monitoring System showing the Laser Beam Transmitter, the Sensor Receiver and the Control Display Component

The transmitter, which is placed on one side of the roadway at the selected measurement-monitoring location, has two laser diodes (in the red color spectrum about 640-to-650-nm wavelength) spaced 12″ apart. The receiver has two photo transistor detectors also spaced 12″ apart. The transmitter is positioned directly across the roadway from the receiver as nearly orthogonal as possible. In operation, the two laser diodes in the transmitter continually emit a pair of parallel beams a small distance above the road surface, and the beams are aligned so that they impinge on the two photo sensor arrays in the receiver across the road. When a vehicle passes through the monitoring location, one beam is interrupted and, a short time later, the second beam is interrupted. The CDC electronics and software accurately measures the time differential between the sequential beam interruptions to determine vehicle speed and, depending on which beam is interrupted first, determines the direction of travel. The CDC—which counts the passing vehicles accumulatively and calculates and displays vehicle speed, direction of travel, and time of event on an LCD—is electrically connected to the receiver. All traffic-monitoring data including the time of each interruption event is recorded on a Compact Flash Memory (CFM) card within the CDC for later review and analysis in an Excel spreadsheet or other data  analysis program. In addition, the CDC has an alphanumeric keypad whereby the set-up technician can enter four initial parameters (Date, Location, Map Book Page, and Map Book Coordinates), which are downloaded to the CFM card as the “Header File.”

The TMS system-level requirements established by my colleague drove the CDC level requirements which I documented. Specifically, the CDC had to be of a size and weight so that it could be easily hand carried. Inexpensive off-the-shelf components were to be utilized to the maximum extent possible in the design and fabrication of the CDC. Power consumption needed to be kept to a minimum. Functionally, the CDC had to be capable calculating speed to within ±1 mph of all vehicles passing through (i.e., “interrupting”) the laser beam pair. In addition, the CDC had to be able to determine the direction of travel, the time the valid interruption occurred, and the cumulative count for all vehicles interrupting the laser beam pair during a manned or unmanned test session. A real-time GUI (i.e., the LCD) and a keypad were also required, as was nonvolatile  memory (CFM card) to store all the traffic pattern data obtained during a traffic-monitoring session.

Figure 2 shows the CDC’s functional elements.

The functions of the main co-processor are to display on the LCD input from the User Interface, to drive the status LEDs and to calculate and display traffic pattern data which is sent to the CFM microcontroller. The CFM microcontroller formats the traffic pattern data in a File Allocation Table (FAT) file and writes that file to the CFM card. Both microcontrollers are clocked by a 40-MHz crystal controlled oscillator and both have an in-circuit serial programming port (ICSP), which allows for programming and reprogramming the microcontrollers at the CDC level. During the software development phase of the project, the ICSP ports were definitely utilized. A power on reset (POR) circuit initializes both microcontrollers at system power-up.

Figure 2: CDC Functional Block Diagram showing the two micro-controllers, the User Interface and the Supporting Functionality

Figure 2: CDC Functional Block Diagram
showing the two micro-controllers,
the User Interface and the Supporting
Functionality

Based on the FBD and the established CDC functional requirements, I designed the CDC motherboard circuit using a schematic capture program. Where necessary, I simulated elements of the circuit using a circuit simulation program. I used an online PCB prototype fabrication service and had to re-enter the schematic using their software. I then laid out and routed the two-sided board using the software package provided by the online vendor. After I submitted the file, it only took a few days to receive the two prototype PCBs I ordered. I “populated” one of the boards with components I had purchased and kept the second board as a spare. Preliminary board-level testing of the assembled PCB revealed two layout errors which were easily corrected by an X-ACTO Knife trace cut and by the addition of a jumper wire.

Figure 3: CDC Motherboard Schematic divided into three sections: (1) Data Processor, (2) CFM Formatter and (3) Input/Output. Some circuitry, such as the RS-422 Interface (U2, U4, J6), was included in the design for potential future utilization but was not used in the prototype configuration.

Figure 3: CDC Motherboard Schematic
divided into three sections: (1) Data
Processor, (2) CFM Formatter and (3)
Input/Output. Some circuitry, such as
the RS-422 Interface (U2, U4, J6), was
included in the design for potential
future utilization but was not used in
the prototype configuration.

Figure 3 depicts the CDC main microcontroller circuit on the motherboard. Photo 3 shows the inside of the CDC with the front panel removed.

As indicated above, I designed and assembled the motherboard circuit card. The LCD module, the keyboard module, the RTC module, and the CFM card module were all purchased assemblies. Once all the parts were installed in the case, I completed the interface wiring.

Photo 3: Inside the CDC showing the (1) Main motherboard, (2) The Main Microcontroller, PIC18F4520, (3) the CFM Micro-controller, PIC18F4520 (4) the LCD module, (5) the Keyboard module, (6) the Real Time Clock module and (7) the CFM Card module, only partially visible.

Photo 3: Inside the CDC showing the (1) Main
motherboard, (2) The Main Microcontroller,
PIC18F4520, (3) the CFM
Micro-controller, PIC18F4520 (4) the
LCD module, (5) the Keyboard module,
(6) the Real Time Clock module and (7)
the CFM Card module, only partially
visible.

The complete article appears in Circuit Cellar 292 (November 2014). Additional files are available on the CC FTP site.

FCC/CE/IC-Certified Bluetooth SMART Beacons

EM Microelectronic’s EMBC01 Bluetooth beacon recently achieved FCC certification for operation within the US, as well as IC certification in Canada and CE certification for operation in the European Union. You can use the compact EMBC01 beacon anywhere iBeacon and Bluetooth Smart v4.0 technologies are implemented.

Source: EM Microelectronic

Source: EM Microelectronic

EMBC01 features, specs, and capabilities:

  • Consumes less than 25 µA average current in a typical application
  • Operates up to 12 months from a single CR2032 battery
  • Includes ultra-low-power EM6819 microprocessor
  • Contains a built-in mode switch
  • Includes an integrated red and green LEDs for status feedback
  • Includes a miniature antenna
  • Detects beacons 75 m away by an iPhone 5S at the 0-dBm output power setting
  • Detects beacons up to 120 m at maximum output power
  • Includes optimized circuit architecture that protects against over-the-air attacks
  • Ships preprogrammed with a Renata CR2032 battery and an IP-64-certified, weatherproof plastic enclosure

The EMBC01, the EMBC01 Development Kit, and accessories are currently available. Contact EM Microelectronic for pricing.

Source: EM Microelectronic

 

 

20-A Step-Down µModule Regulator Optimized for Low VIN to Low VOUT Conversion

Linear Technology Corp. recently introduced the LTM4639, which is 20-A DC/DC step-down µModule (micromodule) regulator. According to Linear, the regulator can convert “2.5 to 7 V main-power system rails to point-of-load voltages as low as 0.6 V.”

Linear Technology LTM4639

Linear Technology LTM4639

The LTM4639—which includes an inductor, DC/DC controller, MOSFETs, and compensation circuitry—is housed in a 4.92-mm BGA package with a 15 mm × 15 mm footprint. For 3.3-V input to 1.5-V output conversion at 20-A load, efficiency is 88%, power loss is 3.9 W, and junction temperature rise above ambient temperature is 37°C. The micromodule regulator provides a precise output voltage regulation. Up to four devices can be paralleled for up to 80-A output while operating out-of-phase to reduce the number of input and output capacitors.

The LTM4639’s input supply range is 2.375 to 7 V. For operation from 3.3 V and lower, a 5-V, low-power auxiliary supply is needed to bias internal circuitry. Output voltage ranges from 0.6 to 5.5 V with protection functions for overcurrent and overvoltage conditions.

The LTM4639 is rated for operation from –40°C to 125°C. The 1,000-piece price is $19.45 each.

Source: Linear Technology

5th International PECCS Conference

The fifth edition of the PECCS conference (5th International Conference on
Pervasive and Embedded Computing and Communication Systems) organized by INSTICC (Institute for Systems and Technologies of Information, Control and Communication) will take place from the February 11-13, 2015 in Angers, Loire Valley, France.Peccs_2015_1

Pervasive and embedded computing and communication is a paradigm that aims at providing trustworthy computing solutions and communication services all the time and everywhere. This entails the need for an interdisciplinary field of R&D that combines signal processing with computer hardware and software technologies, and utilizes and integrates pervasive, wireless, embedded, wearable and/or mobile systems. Applications range from ambient intelligence to ubiquitous multimedia, multidimensional signal processing, sensors, robotics, integrated communication systems and nanotechnologies. PECCS will bring together researchers, engineers and practitioners interested in the theory and applications in these areas.

One of the most important contributions that PECCS brings about is the creation of a high-level forum in collaboration with the most prestigious internationally recognized experts, including names such as Muriel Medard (Massachusetts Institute of Technology, United States), Alois Ferscha (Johannes Kepler Universität Linz, Austria), Bran Selic (University of Toronto, Canada), and Ian White (University of Cambridge, United Kingdom). Each will deliver a keynote lecture reflecting their knowledge on Mobile and Pervasive Computing, Digital Signal Processing and Embedded Systems Design.

All accepted papers will be published in the conference proceedings, under an ISBN reference, on paper and on CD-ROM support. SCITEPRESS is a member of CrossRef and every paper is given a DOI (Digital Object Identifier). All papers presented at the conference venue will be available at the SCITEPRESS Digital Library. The proceedings will be submitted for indexation by Thomson Reuters Conference Proceedings Citation Index (ISI), INSPEC, DBLP, EI (Elsevier Index) and Scopus.

The main sponsor of this conference is INSTICC, in collaboration with several other international associations and institutions related to its main topic areas.

Further information about PHOTOPTICS 2015 can be found at the conference website.

# # #

About INSTICC

INSTICC is the Institute for Systems and Technologies of Information, Control and Communication, a scientific, non-profit, association whose main goals are to serve the international scientific community by promoting, developing and disseminating knowledge in the areas of information systems and technologies, control and communications.

To achieve these goals, INSTICC is committed to integrate and support many activities relevant for the international scientific community, including:

  • Promotion of the mobility of renowned researchers, usually involved as keynote speakers at INSTICC events, so that they can share their knowledge with conference delegates;
  • Providing grants to support the presence of many young researchers from all over the world, especially from regions facing economic difficulties, who wish to attend INSTICC conferences;
  • Publication of proceedings, books and journals – some of them in cooperation with distinguished international publishers – widely indexed and made available at appropriate digital libraries;
  • Sponsorship of research projects, proposed by universities and R&D institutes, related to INSTICC main interest areas;
  • Collaboration with international associations, who may technically  co-sponsor INSTICC events, as well as with companies involved in R&D or supporting of the international academic community.

Over the years, these initiatives have brought together a large and very diversified international community spread over more than 141 countries, including more than 500 high profile keynote speakers, over 15600 specialized reviewers and about 46000 authors.