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Circuit Cellar's editorial team comprises professional engineers, technical editors, and digital media specialists. You can reach the Editorial Department at editorial@circuitcellar.com, @circuitcellar, and facebook.com/circuitcellar

Electrical Engineering Crossword (Issue 294)

The answers to Circuit Cellar’s January 2015 electronics engineering crossword puzzle are now available.294-crossword-(key)

Across

  1. SHIELD—Conductive cover that isolates equipment from electromagnetic interference
  2. TRIMPOT—SMALL POTENTIOMETER FOR MAKING PREDETERMINED MODIFICATIONS IN A CIRCUIT
  3. NINE—A nonet is a grouping of what?
  4. LIMITER—A device that prevents signal peaks from exceeding max levels
  5. HERTZ—One cycle per second.
  6. DIP—Dual inline package
  7. QUALITYCONTROL—QC
  8. MOCKUP—Non-working model of a system
  9. PETABYTE—1 quadrillion bytes
  10. PATCH—Reroute a signal to a different circuit
  11. RF—Electromagnetic signals with frequency > 70 kHz

Down

  1. SMOOTHINGCIRCUIT—A filter for removing spurious noise from a power supply
  2. EXTENSIBLE—“X”
  3. POINTSOURCE—Small energy source that has no effect on its directivity
  4. SHUNT—Component that bypasses another component
  5. GERMANIUM—Semiconductor material used in solid-state diodes and photocells
  6. DAMP—Suppress resonance
  7. DYNE—10 micronewtons
  8. CBAR—0.01 bar
  9. ERG—10–7 joules

Electrical Engineering Crossword (Issue 293)

The answers to Circuit Cellar’s December electronics engineering crossword puzzle are now available.293-crossword-(key)

Across

  1. AMPACITY—Max electrical current
  2. HUMREDUCTION—Use a bridge rectifier driven from an 8- to 12-V transformer winding, a capacitive filter, and a three-terminal IC voltage regulator to achieve this [two words]
  3. EMI—Radiated spurious EM energy
  4. BINARY—Offs and Ons
  5. PASCAL—1 newton/cm2
  6. QUARTZ—Timing crystal
  7. ETCHING—The production of a printed circuit through the removal of unwanted areas of copper foil from a circuit board
  8. CROSSTALK—Caused when one circuit’s signal creates an unwanted effect on another
  9. BUCK—Switched-mode power supply converter
  10. BETATRON—Designed to accelerate electron
  11. BIDIRECTIONAL—Radiating toward or receiving from the front and back only
  12. CRYOTRON—Operates via superconductivity

Down

  1. STOKESSHIFT—Can reduce photon energy [two words]
  2. INPUT—Signal in
  3. ATTO—0.000000000000000001
  4. NOISECANCELLATION—Eliminates out-of-phase information [two words]
  5. MAL—10 Decimals equals?
  6. RAMP—Linearly rising signal
  7. FORCE—Newton
  8. KEYED—OOK is on/off what?
  9. BUS—Common path for several signals

Electrical Engineering Crossword (Issue 292)

The answers to Circuit Cellar’s November electronics engineering crossword puzzle are now available.292-crossword-(key)

Across

  1. BITS—A nibble is 4 of these
  2. REPEATER—ELECTRONIC DEVICE THAT RECEIVES AND AMPLIFIES A WEAK SIGNAL BEFORE RETRANSMITTING IT
  3. MICRO—Metric Prefix for 0.000001
  4. PATCH—To re-route a signal to a different circuit
  5. TOKEN—Used for authentication
  6. RELAY—A switch that is actuated by another electrical signal
  7. JITTER—The deviation of some aspect of a digital signal’s pulses
  8. RHEOSTAT—A variable resistor
  9. LUX—Lx
  10. VOLTA—Italian physicist who invented the first batteries
  11. GERMANIUM—Ge
  12. CONDUIT—Wire piping
  13. PIGTAIL—Short wire connecting components
  14. RECTIFIER—A diode, used for converting AC into DC

Down

  1. SCHOTTKY—High-speed diode that has very little junction capacitance
  2. PEERTOPEER—P2P
  3. INRUSH—A sudden input current surge
  4. CRESTFACTOR—The ratio of the peak value to the RMS value (two words)
  5. MICROFARAD—1,000,000 pF
  6. ANALOG—Constant signal processing

 

 

Issue 294: EQ Answers

Problem 1—Let’s get back to basics and talk about the operation of a capacitor. Suppose you have two large, flat plates that are close to each other (with respect to their diameter). If you charge them up to a given voltage, and then physically move the plates away from each other, what happens to the voltage? What happens to the strength of the electric field between them?

Answer 1—The capacitance of the plates drops with increasing distance, so the voltage between them rises, because the charge doesn’t change and the voltage is equal to the charge divided by the capacitance. At first, while the plate spacing is still small relative to their diameter, The capacitance is proportional to the inverse of the spacing, so the voltage rises linearly with the spacing. However, as the spacing becomes larger, the capacitance drops more slowly and the voltage rises at a lower rate as well.

While the plate spacing is small, the electric field is almost entirely directly between the two plates, with only minor “fringing” effects at the edges. Since the voltage rise is proportional to the distance in this regime, the electric field (e.g., in volts per meter) remains essentially constant. However, once the plate spacing becomes comparable to the diameter of the plates, and fringing effects begin to dominate, the field begins to spread out and weaken. Ultimately, at very large distances, at which the plates themselves can be considered points, the voltage is essentially constant, and the field strength directly between them becomes proportional to the inverse of the distance.


Problem 2—If you double the spacing between the plates of a charged capapcitor, the capacitance is cut in half, and the voltage is doubled. However, the energy stored in the capacitor is defined to be E = 0.5 C V2. This means that at the wider spacing, the capacitor has twice the energy that it had to start with. Where did the extra energy come from?

Answer 2—There is an attractive force between the plates of a capacitor created by the electric field. Physically moving the plates apart requires doing work against this force, and this work becomes the additional potential energy that is stored in the capacitor.


Question 3—What happens when a dielectric is placed in an electric field? Why does the capacitance of pair of plates increase when the space betwenn them is filled with a dielectric?

Answer 3—Dielectric materials are made of atoms, and the atoms contain both positive and negative charges. Although neither the positive nor the negative charges are free to move about in the material (which is what makes it an insulator), they can be shifted to varying degress with respect to each other. An electric field causes this shift, and the shift in turn creates an opposing field that partially cancels the original field. Part of the field’s energy is absorbed by the dielectric.

In a capacitor, the energy absorbed by the dielectric reduces the field between the plates, and therefore reduces the voltage that is created by a given amount of charge. Since capacitance is defined to be the charge divided by the voltage, this means that the capacitance is higher with the dielectric than without it.


Problem 4—What is the piezoelectric effect?

Answer 4—With certain dielectrics, most notably quartz and certain ceramics, the displacement of charge also causes a significant mechanical strain (physical movement) of the crystal lattice. This effect works two ways — a physical strain also causes a shift in electric charges, creating an electric field. This effect can be exploited in a number of ways, including transducers for vibration and sound (microphones and speakers), as well as devices that have a strong mechanical resonance (e.g., crystals) that can be used to create oscillators and filters.

Contributed by David Tweed

Issue 292: EQ Answers

Problem 1—Let’s talk about noise! There are different types of noise that might be present in a system, and it’s important to understand how to deal with them.

For example, analog sensors and other types of active devices will often have AWGN, or Additive White Gaussian Noise, at their outputs. Any sort of analog-to-digital converter will add quantization noise to the data. What is the key difference between these two types of noise?

Answer 1—The key difference between AWGN and quantization noise is the PDF, or Probability Density Function, which is a description of how the values (voltage or current levels in analog systems, or data values in digital systems) are distributed.

The values from AWGN have a bell-shaped distribution, known variously as a Gaussian or Normal distribution. The formula for this distribution is:292-EQ-equation

µ represents the mean value, which we take to be zero in discussions about noise. σ is known as the “standard deviation” of the distribution, and is a way to characterize the “width” of the distribution.

It looks like this:

292-EQ-graph

Source: Wikipedia (en.wikipedia.org/wiki/File:Standard_deviation_diagram.svg)

While the curve is nonzero everywhere (from –∞ to +∞) it is important to note that the values will be within ±1 σ of the mean 68% of the time, within ±2 σ of the mean 95% of the time, and within ±3 σ of the mean 99.7% of the time. In other words, although the peak-to-peak value of this kind of noise is theoretically infinite, you can treat it as being less than 4σ 95% of the time.

On the other hand, the values from quantization noise have a uniform distribution — the values are equally probable, but only over a fixed span that’s equal to the quantization step size of the converter. The peak-to-peak range of this noise is equal to the converter’s step size (resolution).

However, it’s important to note that both sources of noise are “white”, which is a shorthand way of saying that their effects are uniformly distributed across the frequency spectrum.


Problem 2—Signal-to-noise ratios are most usefully described as power ratios. How does one characterize the power levels for both AWGN and quantization noise?

Answer 2—The power of a noise signal is proportional to the square of its RMS value.

The RMS value of AWGN is numerically equal to its standard deviation.

The RMS value of quantization noise is simply the peak-to-peak value (the step size of the converter) divided by √12, or VRMS = 0.2887 VPP. This is easily derived if you characterize the quantization noise signal as a small sawtooth wave that gets added to the analog signal.


Question 3—When you have multiple sources of noise in a system, how can you characterize their combined effect on the overall system performance?

Answer 3—When combining noise sources, you can’t simply add their RMS voltage or current values together. From one sample to the next, one noise source might partially cancel the effects of the other noise source(s).

Instead, you add the individual noise power levels to come up with an overall noise power level. Since power is proportional to voltage (or current) squared, this means that you need to square the individual RMS measurements, add them together, and then take the square root of the result in order to get an equivalent overall RMS value.

VRMS(total) = √(VRMS(n1)2 + VRMS(n2)2 + …)


Problem 4—Broadband analog sensors and other active devices often specify their noise levels in units of “microvolts per root-Hertz” (µV/√Hz) or “nanoamps per root-Hertz” (nA/√Hz). Where does this strange unit come from, and how do you use it?

Answer 4—As described in the previous answer, uncorrelated noise sources are added based on their power. With AWGN, the noise in one “segment” of the frequency spectrum is not correlated with another segment of the spectrum, so if you have a particular voltage level of noise in, say, a 1-Hz band of frequencies, you’ll have √2 times as much noise in a 2-Hz band of frequencies. In general, the RMS noise level for any particular bandwidth is going to be proportional to the square root of that bandwidth, which is why the devices are characterized that way.

So, if you have an opamp that’s characterized as having a noise level of 2 µV/√Hz, and you want to use this in an audio application with a bandwidth of 20 kHz, the overall noise at the output of the opamp will be 2 µV × √20000, or about 283 µVRMS. If your signal is a sinewave with a peak-to-peak value of 1V (353 mVRMS), you’ll have a signal-to-noise ratio of about 124 dB.

Contributed by David Tweed

Dual Ethernet Module Operates as Independent Ports or Switch

The NetBurner MOD54417 network core module provides 10/100 Ethernet connectivity with two Ethernet ports. The ports can operate independently, each with its own MAC address, or as an Ethernet switch, simplifying network infrastructure (i.e., daisy chaining) by enabling Ethernet devices to connect through it.

Source: NetBurner

Source: NetBurner

The module is industrial temperature rated (–40 to +85°C) and also provides: 8 UARTs, 4 I2C, 2 CAN, 3 SPI, 1-Wire, a MicroSD flash card socket, 42 digital I/O, eight 12-bit analog-to-digital inputs, two 12-bit digital-to-analog outputs, and five PWM outputs.  Wireless 802.11 b/g/n communication is available with the optional Wi-Fi add-on.

The NetBurner Network Development Kit (NNDK) provides a complete software and tools package including the Real-Time Operating System, full featured TCP/IP Stack, Web Server, DHCP Server, Eclipse development environment, C/C++ compiler and debugger.  The NNDK is focused on ease of use and you will have your first custom program running within a few hours of receiving the kit. The price of the MOD54417 ranges $94 to $129.

Source: NetBurner

New STM32 Micrcontrollers in Small Memory Sizes

STMicroelectronics’s new STM32F446 microcontrollers feature ARM Cortex-M4 based processing combined with 256- or 512-KB on-chip flash memory options. In addition to using STMicro’s ART Accelerator, the microcontrollers feature smart architecture, advanced flash technology, and an embedded ARM Cortex-M4 core to achieve a performance of 225 DMIPS and 608 CoreMark at 180 MHz executing from embedded flash.

Source: STMicroelectronics

Source: STMicroelectronics

Key features include:

  • At 180 MHz, the STM32F446 delivers 225 DMIPS/608 CoreMark performance executing from flash memory with 0-wait states. The DSP instructions and the floating-point unit expand the range of addressable applications.
  • Using a 90-nm process, the current consumption in Run mode and executing from flash memory is as low as 200 µA/MHz at 180 MHz. In Stop mode, the power consumption is 50 µA typical.
  • Two dedicated audio PLL, SPDIF input, three half-duplex I²S, and two serial audio interfaces (SAI) supporting full-duplex I²S as well as time division multiplex (TDM) mode.
  • Up to 20 communication interfaces (including 4x USARTs plus 2x UARTs running at up to 11.25 Mbps, 4x SPI running at up to 45 Mbps, 3x I²C with a new optional digital filter capability, 2x CAN, SDIO, HDMI CEC and camera interface)
  • Two 12-bit DACs, three 12-bit ADCs reaching 2.4 MSPS or 7.2 MSPS in interleaved mode up to 17 timers: 16- and 32-bit running at up to 180 MHz
  • Easily extendable memory range using the flexible 90-MHz memory controller with a 32-bit parallel interface, and supporting Compact Flash, SRAM, PSRAM, NOR, NAND and SDRAM memories
  • Cost-effective NOR flash extension with the 90-MHz Dual quadSPI interface supporting memory-mapped mode
  • STM32F446 samples are now available for lead customers. Volume production is scheduled for Q1 2015 in packages from a tiny WLCSP81 measuring 3.728 × 3.85 mm to a 20 × 20 mm LQFP144 with 256- or 512-KB flash memory, all with 128-KB SRAM. Pricing starts at $3.75 for the STM32F446RC in a 64-pin LQFP64 package with 256-KB flash memory and 128-KB SRAM for orders of 10,000 units.

Source: STMicroelectronics

Mouser’s New Motor Control Application Site

Mouser Electronics recently launched a new Motor Control Applications site for motor control engineers and anyone interested in control applications. The site features motor control resources and offers components available from Mouser Electronics for building motor control systems.

The site’s Applications section segments motor control into five main subsections: Permanent Magnet Synchronous motors, Brushless DC motors, Stepper motors,AC Induction motors, and Low Voltage DC motors. These subsections describe each motor’s use and operation. You can view functional block diagrams explanations of each block, as well as a parts list of products available for same-day shipping.

Source: Mouser

Source: Mouser

The Articles section covers topics such as Introduction to Rotary Resolvers & Encoders and Passive Components for Advanced Motor Control.

The Featured Products section focuses on key products available from Mouser.com that speed and enhance the construction of motor control systems. Products include the Vishay Widebody VOW3120 2.5A IGBT and MOSFET Driver, Molex Sealed Industrial USB Solutions, and the Fairchild FAN9673 CCM PFC Controller. Additional products for motor control systems include products for EMI suppression, circuit protection, passives, sensors, and motor control development kits.

The Resources section features videos, application notes, and white papers that cover topics such as device selection and system considerations when designing motor control systems. Systems discussed include selecting motor drivers, implementing control feedback loops, Power Factor Correction (PFC) techniques, and designing for thermal management.

Source: Mouser

New Power Factor-Corrected AC-DC Drivers for LED Lighting Apps

ON Semiconductor has announced two new series of power factor corrected (PFC) offline AC-DC drivers for high performance LED lighting applications. Extending the NCL3008x family of products, the NCL30085, NCL30086, and NCL30088 address single-stage design implementations up to 60 W that require high power factor. The NCL30030 broadens the existing solutions which support higher power (up to 150 W) two-stage topologies that require low optical ripple and wide LED forward voltage variation.

 

Source: ON Semiconductor

Source: ON Semiconductor

The NCL30085, NCL30086, and NCL30088 use a PFC current control algorithm that makes them suitable for flyback buck-boost and SEPIC topologies. By operating in quasi-resonant mode, they can deliver optimum efficiency across wide line and load levels. The innovative control methodology enables strict current regulation to be achieved (within 2% typically) solely from the primary side.

 

The non-dimmable NCL30088 is complemented by the “smart-dimmable” NCL30086, supporting analog and pulse-width modulation (PWM) dimming with a single input that controls the average LED current. Completing the series is the NCL30085, which supports three levels of log step dimming: 70%, 25%, and 5%. As a result, it permits light output reduction by toggling the AC switch on/off to signal the controller to lower the LED current point. All three devices feature user-configurable current thermal fold-back mechanisms that help prevent overheating and enable manufacturers to support longer lifetime warranties.

 

The NCL30085 and NCL30088 are available in SOIC-8 packages. The NCL30086 is offered in an SOIC-10 package with pricing of the series starting at $0.35 per unit in 10,000-piece quantities.

 

The NCL30030 is a two-stage PFC controller plus quasi-resonant flyback controller optimized for medium and high power LED lighting applications up to 150 W. This device is best suited for commercial lighting such as lowbay, highbay, and streetlighting. The NCL30030 makes use of a proprietary multiplier architecture to achieve low harmonic distortion and near-unity power factor while operating in critical conduction mode (CrM).

The NCL30030 is in an SOIC−16 package with one pin removed for high-voltage spacing. Pricing starts at $0.65 per unit in 10,000-piece quantities.

 

Source: ON Semiconductor

LED Light Engines Deliver Up to 4,000 Lumens

Innovations in Optics has announced  high-power white LED light engines for OEM fiberoptic illumination. LumiBright Light Engines couple directly to liquid light guides and fiber bundles with no additional optics. They deliver up to 4,000 lumens into the light guide.

The 2400-W (Source:

The 2400-W (Source: Innovations in Optics)

Offering substantial cost and operational advantages, white LEDs are becoming popular light guide illumination sources for many technical applications that were historically dominated by tungsten halogen and HID lamps. LumiBright light engines feature patented technologies that encompass non-imaging optics with chip-on-board (COB) LED arrays on metal core circuit boards to provide both optimum luminous efficacy and ideal thermal management. Unlike the so called “big chip” LEDs used in many light guide illuminators, LumiBright light engines feature large source size and emit into a numerical aperture that matches the acceptance cone angle and diameter of light guide systems. The unique design results in many more lumens emitted from light guides relative to the big chip Lambertian emitters.

The LumiBright 2400B-400-W has a 0.66 numerical aperture (NA) and illuminates fiber bundles and light guides sized from 6.0 to 8.0 mm in diameter. Well suited for applications in machine vision and remote source illumination, the light engine generates up to 4,000 lumens. The 2400B-500-W is ideally suited for endoscope and microscope illuminator applications with a 0.60 NA for light guides that are 3.0 to 5.0 mm in diameter. The 2400B-500-W produces up to 1,500 lumens. Available light engine system accessories include thermal management devices, wire harnesses, and driver/controllers.

Source: Innovations in Optics

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.