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Quad Bench Power Supply

The need for a bevy of equipment for building and testing presents a problem: how to deliver an adequate power supply while keeping workbench clutter to a minimum. Brian decided to tackle this classic engineering conundrum with a small, low-capacity quad bench power supply.

To the right of the output Johnson posts are the switches that set the polarity of the floating supplies—as well as the switch that disconnects all power supply outputs—while leaving the unit still powered up.

To the right of the output Johnson posts are the switches that set the polarity of the floating supplies—as well as the switch that disconnects all power supply outputs—while leaving the unit still powered up.

In “Quad Bench Power Supply,” Millier writes:

I hate to admit it, but my electronics bench is not a pretty sight, at least in the midst of a project anyway. Of course, I’m always in the middle of some project that, more often than not, contains two or three different projects in various stages of completion. To make matters worse, most of my projects involve microchips, which have to be programmed. Because I use ISP flash memory MCUs exclusively, it makes sense to locate a computer on my construction bench to facilitate programming and testing. To save space, I initially used my laptop’s parallel port for MCU programming. It was only a matter of time before I popped the laptop’s printer port by connecting it to a prototype circuit with errors on it.

Fixing my laptop’s printer port would have involved replacing its main board, which is an expensive proposition. Therefore, I switched over to a desktop computer (with a $20 ISA printer port board) for programming and testing purposes. The desktop, however, took up much more room on my bench.

You can’t do without lots of testing equipment, all of which takes up more bench space. Amongst my test equipment, I have several bench power supplies, which are unfortunately large because I built them with surplus power supply assemblies taken from older, unused equipment. This seemed like a good candidate for miniaturization.

At about the same time, I read a fine article by Robert Lacoste describing a high-power tracking lab power supply (“A Tracking Lab Power Supply,” Circuit Cellar 139). Although I liked many of Robert’s clever design ideas, most of my recent projects seemed to need only modest amounts of power. Therefore, I decided to design my own low-capacity bench supply that would be compact enough to fit in a small case. In this article, I’ll describe that power supply.

MY WISH LIST

Even though I mentioned that my recent project’s power demands were fairly modest, I frequently needed three or more discrete voltage levels. This meant lugging out a couple of different bench supplies and wiring all of them to the circuit I was building. If the circuit required all of the power supplies to cycle on and off simultaneously, the above arrangement was extremely inconvenient. In any event, it took up too much space on my bench.

I decided that I wanted to have four discrete voltage sources available. One power supply would be ground referenced. Two additional power supplies would be floating power supplies. Each of these would have the provision to switch either the positive or negative terminal to the negative (ground) terminal of the ground-referenced supply, allowing for positive or negative output voltage. Alternately, these supplies could be left floating with respect to ground by leaving the aforementioned switch in the center position.

This arrangement allows for one positive and two positive, negative or floating voltage outputs. To round off the complement, I added Condor’s commercial 5-V, 3-A linear power supply module, which I had on hand in my junk box. Table 1 shows the capabilities of the four power supplies.

I wanted to provide the metering of voltage and current for the three variable power supplies. The simultaneous voltage and current measurement of three completely independent power supplies seemed to indicate the need for six digital panel meters. Indeed, this is the path that Robert Lacoste used in his tracking lab supply.

As you can see, there are four power supplies. I’ve included all of the information you need to understand their capabilities.

As you can see, there are four power supplies. I’ve included all of the information you need to understand their capabilities.

I had used many of these DPM modules before, so I was aware of the fact that the modules require their negative measurement terminal to float with respect to the DPM’s own power supply. I solved this problem in the past by providing the DPM module with its own independent power source. Robert solved it by designing a differential drive circuit for the DPM. Either solution, when multiplied by six, is not trivial. Add to this the fact that high-quality DPMs cost about $40 in Canada, and you’ll see why I started to consider a different solution.

I decided to incorporate an MCU into the design to replace the six DPMs as well as six 10-turn potentiometers, which are also becoming expensive. In place of $240 worth of DPMs, I used three inexpensive dual 12-bit ADCs, an MCU, and an inexpensive LCD panel. The $100 worth of 10-turn potentiometers was replaced with three dual digital potentiometers and two inexpensive rotary encoders.

Using a microcontroller-based circuit basically allows you to control the bench supply with a computer for free. I have to admit that I decided to add the commercial 5-V supply module at the last minute; therefore, I didn’t allow for the voltage or current monitoring of this particular supply.

THE ANALOG CORE

Although there certainly is a digital component to this project, the basic power supply core is a standard analog series-pass regulator design. I borrowed a bit of this design from Robert’s lab supply circuit.

Basically, all three power supplies share the same design. The ground-referenced power supply provides less voltage and more current than the floating supplies. Thus, it uses a different transformer than the two floating supplies. The ground-referenced supply’s digital circuitry (for control of the digital potentiometer and ADC) can be connected directly to the MCU port lines. The two floating supplies, in addition to the different power transformer, also need isolation circuitry to connect to the MCU.

Figure 1 is the schematic for the ground-referenced supply. As you can see, a 24VCT PCB-mounted transformer provides all four necessary voltage sources. A full wave rectifier comprised of D4, D5, and C5 provides the 16 V that’s regulated down to the actual power supply output. Diodes D6, R10, C8, and Zener diode D7 provide the negative power supply needed by the op-amps. …

The ground-referenced power supply includes an independent 5-V supply to run the microcontroller module.

The ground-referenced power supply includes an independent 5-V supply to run the microcontroller module.

MCU AND USER INTERFACE

As with every other project I’ve worked on in the last two years, I chose the Atmel AVR family for the MCU. In this case, I went with the AT90S8535 for a couple of reasons. I needed 23 I/O lines to handle the three SPI channels, LCD, rotary encoders, and RS-232. This ruled out the use of smaller AVR devices. I could’ve used the slightly less expensive AT90LS8515, but I wanted to allow for the possibility of adding a temperature-sensing meter/alarm option to the circuit. The ’8535 has a 10-bit ADC function that’s suitable for this purpose; the ’8515 does not.

The ’8535 MCU has 8 KB of ISP flash memory, which is just about right for the necessary firmware. It also contains 512 bytes of EEPROM. I used a small amount of the EEPROM to store default values for the three programmable power supplies. That is to say, the power supply will power up with the same settings that existed at the time its Save Configuration push button was last pressed.

To simplify construction, I decided to use a SIMM100 SimmStick module made by Lawicel. The SIMM100 is a 3.5″ × 2.0″ PCB containing the ’8535, power supply regulator, reset function, RS-232 interface, ADC, ISP programming headers, and a 30-pin SimmStick-style bus. I’ve used this module for prototypes several times in the past, but this is the first time I’ve actually incorporated one into a finished project. …

eded to operate the three SPI channels and interface the two rotary encoders come out through the 30-pin bus. As you now know, I designed the ground-referenced power supply PCB to include space to mount the SIMM100 module, as well as the IsoLoop isolators. The SIMM100 mounts at right angles to this PCB; it’s hard-wired in place using 90° header pins. The floating power supplies share a virtually identical PCB layout apart from being smaller because of the lack of traces and circuitry associated with the SIMM100 bus and IsoLoop isolators.

The SIMM100 module has headers for the ISP programming cable and RS-232 port. I used its ADC header to run the LCD by reassigning six of the ADC port pins to general I/O pins.

When I buy in bulk, it’s inevitable that by the time I use the last item in my stock, something better has taken its place. After contacting Lawicel to request a .jpg image of the SIMM100 for this article, I was introduced to the new line of AVR modules that the company is developing.

Rather than a SimmStick-based module, the new modules are 24- and 40-pin DIP modules that are meant to replace Basic Stamps. Instead of using PIC chips/serial EEPROM and a Basic Interpreter, they implement the most powerful members of Atmel’s AVR family—the Mega chips.

Mega chips execute compiled code from fast internal flash memory and contain much more RAM and EEPROM than Stamps. Even though flash programming AVR-family chips is easy through SPI, using inexpensive printer port programming cables, these modules go one step further by incorporating RS-232 flash memory programming. This makes field updates a snap. …

The user interface I settled on consisted of a common 4 × 20 LCD panel along with two rotary encoders. One encoder is used to scroll through the various power supply parameters, and the other adjusts the selected parameter. The cost of LCDs and rotary encoders is reasonable these days. Being able to eliminate the substantial cost of six DPMs and six 10-turn potentiometers was the main reason for choosing an MCU-based design in the first place.

Brian Millier’s article first appeared in Circuit Cellar 149.

ARM MCUs wtith Capacitive Touch Hardware Support for HMI and LIN Applications

Atmel recently announced its next-generation family of automotive-qualified ARM Cortext-M0+-based micrcontrollers with an integrated peripheral touch controller (PTC) for capacitive touch applications. The new SAM DA1 is the first series in this Atmel |SMART MCU automotive-qualified product family, operating at a maximum frequency of 48 MHz and reaching a 2.14 Coremark/MHz.Atmel Corporation SAM DA1

Atmel’s SAM DA1 series is ideal for capacitive touch button, slider, wheel or proximity sensing applications and offers high analog performance for greater front-end flexibility. The new devices are available down to a very compact QFN 5 × 5 mm package with wettable flanks for automated optical inspection.

Eliminating external components and offering more robust features, devices in the SAM DA1 series come with 32 to 64 pins, up to 64 KB of flash memory, 8 KB of SRAM, and 2-KB read-while-write flash memory and are qualified according to the AEC Q-100 Grade 2 (–40° to 105°C).

Key Features of Atmel’s SAM DA1 Series

  • Atmel |SMART ARM Cortex-M0+-based processor
  • 45 DMIPS
  • Vcc 2.7 to 3.63 V
  • 16- to 64-KB Flash; 32 to 64 pins
  • Up to six SERCOM (Serial Communication Interface), USB, I2S
  • Peripheral Touch Controller
  • Complex PWM
  • AEC Q100 Grade 2 Qualified

To accelerate the design development, the ATSAMDA1-XPRO development kit is available to support the new devices. The new SAM DA1 series is also supported by Atmel Studio, Atmel Software Framework and debuggers.

Contact Atmel to sample the SAM DA1 series.

Source: Atmel

Security Agents for Embedded Intrusion Detection

Knowingly or unknowingly, we interact with hundreds of networked-embedded devices in our day-to-day lives such as mobile devices, electronic households, medical equipment, automobiles, media players, and many more. This increased dependence of our lives on the networked-embedded devices, nevertheless, has raised serious security concerns. In the past, security of embedded systems was not a major concern as these systems were a stand-alone network that contained only trusted devices with little or no communication to the external world. One could execute an attack only with a direct physical or local access to the internal embedded network or to the device. Today, however, almost every embedded device is connected to other devices or the external world (e.g., the Cloud) for advanced monitoring and management capabilities. On one hand, enabling networking capabilities paves the way for a smarter world that we currently live in, while on the other hand, the same capability raises severe security concerns in embedded devices. Recent attacks on embedded device product portfolios in the Black Hat and Defcon conferences has identified remote exploit vulnerabilities (e.g., an adversary who exploits the remote connectivity of embedded devices to launch attacks such as privacy leakage, malware insertion, and denial of service) as one of the major attack vectors. A handful of research efforts along the lines of traditional security defenses have been proposed to enhance the security posture of these networked devices. These solutions, however, do not entirely solve the problem and we therefore argue the need for a light weight intrusion-defense capability within the embedded device.

In particular, we observe that the networking capability of embedded devices can indeed be leveraged to provide an in-home secure proxy server that monitors all the network traffic to and from the devices. The proxy server will act as a gateway performing policy based operations on all the traffic to and from the interconnected embedded devices inside the household. In order to do so, the proxy server will implement an agent based computing model where each embedded device is required to run a light weight checker agent that periodically reports the device status back to the server; the server verifies the operation integrity and signals back the device to perform its normal functionality. A similar approach is proposed Ang Cui and Salvatore J. Stolfo’s 2011 paper, “Defending Embedded Systems with Software Symbiotes,” where a piece of software called Symbiote is injected into the device’s firmware that uses a secure checksum-based approach to detect any malicious intrusions into the device.

In contrast to Symbiote, we exploit lightweight checker agents at devices that merely forward device status to the server and all the related heavy computations are offloaded to the proxy server, which in turn proves our approach computationally efficient. Alternatively, the proposed model incurs a very small computational overhead in gathering and reporting critical device status messages to the server. Also, the communication overhead can be amortized under most circumstances as the sensor data from the checker agents can be piggybacked to the original data messages being transferred between the device and the server. Our model, as what’s described in the aforementioned Cui and Stolfo paper, can be easily integrated with legacy embedded devices as the only modification required to the legacy devices is a “firmware upgrade that includes checker agents.”

To complete the picture, we propose an additional layer of security for modern embedded devices by designing an AuditBox, as in the article, “Pillarbox,” by K. Bowers, C. Hart, A. Juels, and N. Triandopoulos. It keeps an obfuscated log of malicious events taking place at the device which are reported back to the server at predefined time intervals. This enables our server to act accordingly by either revoking the device from the network or by restoring it to a safe state. AuditBox will enforce integrity by being able to verify whether the logs at the device have been tampered with by an adversary who is in control of the device and covertness by hiding from an attacker with access to the device whether the log reports detection of malicious behavior. To realize these requirements, AuditBox will exploit the concept of forward secure key generation.

Embedded systems security is of crucial importance and the need of the hour. Along with the advancement in embedded systems technology, we need to put an equal emphasis on its security in order for our world to be truly a smarter place.

RESOURCES
K. Bowers, C. Hart, A. Juels, & N. Triandopoulos, “Pillarbox: Combating Next-Generation Malware with Fast Forward-Secure Logging,” in Research in Attacks, Intrusions and Defenses, ser. Lecture Notes in Computer Science, A. Stavrou, H. Bos, and G. Portokalidis (Eds.), Springer, 2014, http://dx.doi.org/10.1007/978-3-319-11379-1_3.

A. Cui & S. J. Stolfo, “Defending embedded systems with software symbiotes,” in Proceedings of the 14th international conference on Recent Advances in Intrusion Detection (RAID’11), R. Sommer, D. Balzarotti, and G. Maier (Eds.), Springer-Verlag, 2011, http://dx.doi.org/10.1007/978-3-642-23644-0_19.

DevuDr. Devu Manikantan Shila is the Principal Investigator for Cyber Security area within the Embedded Systems and Networks Group at the United Technologies Research Center (UTRC).

 

Marten van DijkMarten van Dijk is an Associate Professor of Electrical and Computing Engineering at the University of Connecticut, with over 10 years research experience in system security both in academia and industry.

 

Syed Kamran HaiderSyed Kamran Haider is pursuing a PhD in Computer Engineering supervised by Marten van Dijk at the University of Connecticut.

 

This essay appears in Circuit Cellar 297 (April 2015).

Energy-Friendly IC and Evaluation Kit for iOS Accessory Development

Silicon Labs now offers a digital audio bridge chip and evaluation kit designed to simplify the development of accessories for iOS devices. Target applications include audio accessories such as guitar and microphone recording dongles, audio docks, and headphones. The CP2614 IC also provides built-in support for communication between iOS applications and accessory hardware, enabling a broad array of Internet of Things (IoT) accessories that operate with a companion iOS app.Silicon Labs CP2614

The CP2614 bridge chip and MFI-SL-CP2614-EK evaluation kit provide a cost-effective, comprehensive development platform for iOS accessory developers, enabling fast time to market through fixed-function MFi support. The CP2614 solution requires no firmware development, which helps developers get up and running quickly with their MFi accessory designs. Developers simply select their customization options with an easy-to-use GUI-based configuration tool.

The CP2614 bridge chip carefully manages and minimizes power consumption, achieving ultra-low power in both active and idle modes. The CP2614 IC’s energy efficiency makes it good choice for device-powered accessories. In addition, the CP2614 includes an integrated 5-V low drop-out (LDO) regulator, which reduces BOM cost and footprint for self-powered accessories. The CP2614 device operates without an external crystal or EEPROM, storing all configuration options on chip. The crystal-less architecture and integrated EEPROM further reduce BOM cost as well as PCB space, enabling developers to design smaller, more streamlined and cost-effective accessories.

 

The CP2614 audio bridge chip supports 24-bit unidirectional and 16-bit bidirectional digital audio streaming, enabling developers to create high-quality, high-performance “prosumer”-class audio accessories. The CP2614 can establish a communications channel with an iOS application, enabling the app to interact directly with the accessory hardware through general-purpose input/output (GPIO) read/writes and access to the UART for custom data flow. The GPIO can be configured for button input and LED output and accessed remotely from an iOS app or used to control audio playback.

 

The CP2614 audio bridge IC and MFI-SL-CP2614-EK evaluation kit are in full production and available to MFi licensees today. Available in a 5 mm x 5 mm QFN32 package, the CP2614 IC is priced at $2.51 (USD) in 10,000-unit quantities. The MFI-SL-CP2614-EK is priced at $59 (USD MSRP). MFi licensees can order the evaluation kit through the Apple MFi Procurement Portal.

Source: Silicon Labs

New USB Controlled Microwave and Millimeter Wave Components

Pasternack has released a new line of USB-controlled microwave and millimeter wave components, which includes amplifiers, attenuators, and PIN diode switches. The new components are controlled and powered by a convenient USB 2.0 port with driverless installation. An external power supply isn’t required.USB-Controlled-RF-Components-SQ

The attenuators and PIN diode switches require an easy-to-use downloadable software program which interfaces with any Windows computer. The company is releasing two models each of the amplifiers, switches and attenuators that cover extremely wide frequency bands up to 40 GHz. The modules are 50-Ω hybrid MIC designs that do not require any external matching components.

Pasternack’s new USB controlled amplifiers offer typical performance of 12 dB gain, 10-dBm P1dB, a 4.5-dB noise figure and operate over a 50 MHz to 18 GHz band or 50 MHz to 40 GHz band. The attenuators offer typical performance of 30 dB attenuation, 5 to 8 dB of insertion loss, a 1-dB step size and are available in two programmable models that cover 100 MHz to 18 GHz and 100 MHz to 40 GHz. Lastly, the SPDT switches offer typical performance 3 to 5 dB of insertion loss, 65 to 70 dB isolation, a 6-µs switching speed and are available in two models that cover 500 MHz to 18 GHz and 500 MHz to 40 GHz. All models operate over a broad temperature range of –40°C to 85°C and depending on the frequency, are available with either female SMA or 2.92-mm connectors.

Source: Pasternack

 

Highly Integrated DC/DC Converter with PMBus Digital Interface

Texas Instruments recently introduced a four-channel buck DC/DC converter with PMBus/I2C digital interface for applications in space-constrained equipment. The TPS65400 dual- or quad-output configurable DC/DC converter integrates eight power MOSFETs. In addition, it features industry-leading efficiency at up to 95% in the smallest footprint.TPS65400 Press Photo

The TPS65400 includes four high-current synchronous buck switching regulators with integrated MOSFETs. Each switching converter supplies a 2- or 4-A output to efficiently power digital circuits, such as the processor, FPGA, ASIC, memory and digital input/output. Switching frequency for the converter is independently adjustable up to 2.2 MHz. The TPS65400 can be powered from a single-input voltage rail between 4.5 and 18 V. It supports applications running off a 5- or 12-V intermediate power distribution bus.

The TPS65400’s benefits and key features include:

  • Flexible power up/down sequencing control increases system reliability.
  • Parameter configuration and status monitoring via PMBus
  • Dynamic voltage scaling to optimize processor performance
  • Phase interleaving reduces input capacitance and ripple
  • Current sharing supports higher output current and enhances design flexibility
  • Small 48-pin VQFN package measures 7 mm × 7 mm × 0.9 mm.

The TPS65400 costs $3.68 in 1,000-unit quantities. The TPS65400EVM-678 evaluation module costs $199.

Source: Texas Instruments

Utilize Simple Radios with Simple Computers

I ordered some little UHF transmitters and receivers from suppliers on AliExpress, the Chinese equivalent of Amazon.com, in order to extend my door chimes into areas of my home where I could not hear them. These ridiculously inexpensive units are currently about $1 per transmitter-receiver pair in quantities of five, including shipping, and are available at 315 and 433.92 MHz. Photo 1 shows a transmitter and receiver pair.  Connections are power and ground and data in or out.

Photo 1: 315 MHz Transmitter-Receiver Pair (Receiver on Left)

Photo 1: The 315-MHz transmitter-receiver pair (receiver on left)

The original attempt at a door chime extender modulated the transmit RF with an audio tone and searched for the presence of that tone at the receiver with a narrow audio filter, envelope detector, and threshold detector. This sort of worked, but I started incorporating the same transmitters into another project that interfered, despite the audio filter.

The other project used Arduino Uno R3 computers and Virtual Wire to convey data reliably between transmitters and receivers. Do not expect a simple connection to a serial port to work well. As the other project evolved, I learned enough about the Atmel ATtiny85 processor, a smaller alternative to the Atmel ATmega328 processor in the Arduino Uno R3, to make new and better and very much simpler circuits. That project evolved to come full circle and now serves as a better doorbell extender. The transmitters self identify, so a second transmit unit now also notifies me when the postman opens the mailbox.

Note the requirement for Virtual Wire.  Do not expect a simple connection to a serial port to work very well.

Transmitter

Figure 1 shows the basic transmitter circuit, and Photo 2 shows the prototype transmitter. There is only the ATtiny85 CPU and a transmitter board. The ATtiny85 only has eight pins with two dedicated to power and one to the Reset input.

Figure 1: Simple Transmitter Schematic

Figure 1: Simple transmitter schematic

One digital output powers the transmitter and a second digital output provides data to the transmitter.  The remaining three pins are available to serve as inputs.  One serves to configure and control the unit as a mailbox alarm, and the other two set the identification message the transmitter sends to enable the receiver to discriminate among a group of such transmitters.

Photo 2: 315 MHz Transmitter and ATtiny85 CPU

Photo 2: The 315-MHz transmitter and ATtiny85 CPU

When input pin 3 is high at power-up, the unit enters mailbox alarm mode. In mailbox alarm mode, the input pins 2 and 7 serve as binary identification bits to define the value of the single numeric character that the transmitter sends, and the input pin 3 serves as the interrupt input. Whenever input pin 3 transitions from high-to-low or low-to-high, the ATtiny85 CPU wakes from SLEEP_MODE_PWR_DOWN, makes a single transmission, and goes back to sleep. The current mailbox sensor is a tilt switch mounted to the door of the mailbox. The next one will likely be a reed relay, so only a magnet will need to move.

When in SLEEP_MODE_PWR_DOWN, the whole circuit draws under 0.5 µA. I expect long life from the three AAA batteries if they can withstand heat, cold, and moisture. I can program the ATtiny to pull the identification inputs high, but each binary identification pin then draws about 100 µA when pulled low. In contrast, the 20- or 22-MΩ pull-up resistors I use as pull-ups each draw only a small fraction of a microampere when pulled low.

When input pin 3 is low at power-up, the unit enters doorbell extender alarm mode. In doorbell extender alarm mode, the input pins 2 and 7 again serve as binary identification bits to define the value of the single numeric character that the transmitter sends; but in doorbell extender mode, the unit repetitively transmits the identification character whenever power from the door chimes remains applied.

Receiver

Figure 2 shows the basic receiver circuit, and Photo 3 shows the prototype receiver. There is only the ATtiny85 CPU with a 78L05 voltage regulator and a receiver board.

Figure 2: Simple Receiver Schematic

Figure 2: Simple receiver schematic

The receiver output feeds the input at pin 5. The Virtual Wire software decodes and presents the received character. Software in the CPU sends tone pulses to a loudspeaker that convey the value of the identification code received, so I can tell the difference between the door chime and the mailbox signals. Current software changes both the number of beep tones and their audible frequency to indicate the identity of the transmit source.

Photo 3: The 315-MHz receiver with ATtiny85 CPU and 78L05 voltage regulator

Photo 3: The 315-MHz receiver with ATtiny85 CPU and 78L05 voltage regulator

Note that these receivers are annoyingly sensitive to power supply ripple, so receiver power must either come from a filtered and regulated supply or from batteries.

Photo 4 shows the complete receiver with the loudspeaker.

Photo 4: Receiver with antenna connections and loudspeaker

Photo 4: Receiver with antenna connections and a loudspeaker

Link Margin

A few inches of wire for an antenna will reach anywhere in my small basement. To improve transmission distance from the mailbox at the street to the receiver in my basement, I added a simple half-wave dipole antenna to both transmitter and receiver. Construction is with insulated magnet wire so I can twist the balanced transmission line portion as in Photo 5. I bring the transmission line out through an existing hole in my metal mailbox and staple the vertical dipole to the wooden mail post. My next mailbox will not be metal.

Photo 5: Simple half-wave dipole for both Tx and Rx increases link distance

Photo 5: Simple half-wave dipole for both Tx and Rx increases link distance

I don’t have long term bad weather data to show this will continue to work through heavy ice and snow, but my mailman sees me respond promptly so far.

Operating Mode Differences

The mailbox unit must operate at minimum battery drain, and it does this very well. The doorbell extender operates continuously when the AC door chime applies power. In order to complete a full message no matter how short a time someone presses the doorbell push button, I rectify the AC and store charge in a relatively large electrolytic capacitor to enable sufficient transmission time.

Photo 6: New PCBs for receive and transmit

Photo 6: New PCBs for receive and transmit

Availability

This unit is fairly simple to fabricate and program your self, but if there is demand, my friend Lee Johnson will make and sell boards with pre-programmed ATtiny85 CPUs. (Lee Johnson, NØVI, will have information on his website if we develop this project into a product: www.citrus-electronics.com.) We will socket the CPU so you can replace it to change the program. The new transmitter and receiver printed circuit boards appear in Photo 6.


Dr. Sam Green (WØPCE) is a retired aerospace engineer living in Saint Louis, MO. He holds degrees in Electronic Engineering from Northwestern University and the University of Illinois at Urbana. Sam specialized in free space and fiber optical data communications and photonics. He became KN9KEQ and K9KEQ in 1957, while a high school freshman in Skokie, IL, where he was a Skokie Six Meter Indian. Sam held a Technician class license for 36 years before finally upgrading to Amateur Extra Class in 1993. He is a member of ARRL, a member of the Boeing Employees Amateur Radio Society (BEARS), a member of the Saint Louis QRP Society (SLQS), and breakfasts with the Saint Louis Area Microwave Society (SLAMS). Sam is a Registered Professional Engineer in Missouri and a life senior member of IEEE. Sam is listed as inventor on 18 patents.

SoC FPGA Development Kit for Audio & Processing Applications

Coveloz recently announced the availability of its Pro Audio Ethernet AVB FPGA Development Kit, which is a ready-to-play platform for building scalable, cost-effective networked audio and processing applications built on modular hardware.Covelozpro-audio-dev-kit

Coveloz introduced its Networked Pro Audio SoC FPGA Development Kit during the Integrated System Europe (ISE) show in Amsterdam. According to the company, the new platform will enable manufacturers to achieve faster AVnu certification for new AVB solutions, creating an ideal development environment for live sound, conferencing systems, public address, audio post production, music creation, automotive infotainment and ADAS applications.

At the heart of the Coveloz development platform is a highly integrated System-on-Module (SOM), featuring an Altera Cyclone V SoC FPGA, which includes a dual-core ARM A9 processor, DDR3 memory and a large FPGA fabric, all in a low cost and compact package. The kit includes a multitude of networking and audio interfaces, including three Gigabit Ethernet ports as well as I2S, AES10/MADI, AES3/EBU and TDM audio.

Coveloz provides FPGA and Linux firmware enabling designers to quickly build AVnu Certified products for the broadcast, pro-audio/video and automotive markets. The platform is aimed at time-synchronized networks and includes grandmaster, PPS and word clock inputs and outputs as well as high quality timing references.

The Coveloz development kit is also host to the BACH-SOC platform, which integrates AES67 and Ethernet AVB audio networking and processing. Both SoC and PCIe-based FPGA implementations are available.

The Coveloz Bach Module is a full-featured and programmable audio networking and processing solution for easily integrating industry-standard AES67 and/or Ethernet AVB/TSN networking into audio/video distribution and processing products. The solution enables products with over 128+128 channels of digital streaming and 32-bit audio processing at 48, 96, or 192 kHz.

Supporting a wide range of interfaces, Coveloz complements the development platform with a comprehensive software toolkit and engineering services to help manufacturers reducing time to market. Coveloz also provides application examples to demonstrate the capabilities of the BACH-SOC platform.

The programmable BACH-SOC can be customized to a particular application in many ways—for instance, from selecting the number and type of audio interface to choosing audio processing alone, transport alone, or a combination.

Source: Coveloz

Online Classroom for Analog Design

Texas Instruments recently launched TI Precision Labs, which is a comprehensive online classroom for analog engineers to take on-demand courses. The free, modular curriculum includes more than 30 training experiences and lab videos covering analog amplifier design considerations with online coursework.TI OnlineClassroomAnalog

TI Precision Labs incorporates a variety of tools to bring the online training experience to life. A $199 TI Precision Labs Op Amp Evaluation Module (TI-PLABS-AMP-EVM) enables engineers to complete each demonstrated learning activity along with the trainer. The curriculum also provides access to free design tools, such as TI Designs reference designs and TI’s TINA-TI SPICE model simulator.

Engineers can evaluate circuits and small-signal AC performance created during the trainings with National Instruments’s VirtualBench all-in-one instrument and TI’s Bode Analyzer Software for VirtualBench, as well as standard engineering bench equipment.

Key features and benefits of TI Precision Labs:

  • Experiential learning applies theory to real-world, hands-on examples with lab demonstration videos.
  • A customized learning environment provides recommended training tracks on topics such as noise, bandwidth and input/output swing, while enabling engineers to pick and choose courses based on individual needs and interests.
  • Accelerated learning for recent graduates eases the transition from undergraduate theoretical-based learning to real-world designing.
  • Robust learning materials include a downloadable presentation workbook and lab manual, as well as TI’s Analog Engineer’s Pocket Reference, which puts commonly used board- and system-level formulas at your fingertips.
  • Expert support: A TI Precision Labs support forum is available on the TI E2E Community to answer questions resulting from the training.

The TI Precision Labs training curriculum is free to anyone with a myTI account. In addition to free training, other benefits of myTI registration include the ability to purchase TI integrated circuits (ICs), evaluation modules, development kits and software; request product samples; get technical assistance through the TI E2E Community; create, simulate and optimize systems in the WEBENCH Design Center; and more.
TI Precision Labs curriculum is housed in the new TI Training Center, which connects engineers with the technical training they need to find solutions to their design challenges anytime, anywhere.

In addition to the on-demand courses, in-person, hands-on trainings covering a variety of precision amplifier topics, such as noise, offset, input bias, slew rate and bandwidth, are scheduled for May in Schaumburg, IL and Pewaukee, WI. Both live trainings require registration and cost $99 to attend. More in-person training dates in the United States will be added.

Source: Texas Instruments

20-µA Op-Amp for 30-µV Precision

Linear Technology’s LT6023 is a dual 3-to-30-V low-power operational amplifier that features 30-µV maximum input offset voltage and 60 µs settling to 0.01%. Proprietary slew enhancement circuitry results in a fast, clean output step response with low power consumption. Specially designed input circuitry maintains high impedance, which minimizes current spikes associated with fast steps for input steps up to 5 V. Together these features make the LT6023 an ideal for portable high-precision instruments, multiplexed data acquisition systems, and DAC buffer applications.Linear LT6023

The LT6023-1 includes a shutdown mode, which reduces the supply current to less than 3 µA when the amplifier is not active. Enable time of 480 µs and fast slew rate combine to provide power-efficient operation in duty-cycled applications, such as those featuring Linear Technology’s Dust Networks wireless sensor network products.

Summary of Features: LT6023

  • 30 µV Max Input Offset Voltage (MSOP Package)
  • Excellent Slew Rate to Power Consumption Ratio
  • 1 V/µs Slew Rate (10 V step)
  • 20 µA Max Supply Current
  • 3 nA Max Input Bias Current
  • 3 V to 30 V Supply Range
  • Output Swings Rail-to-Rail
  • –40°C to 125°C Specified Temperature Range
  • 3 A Max Shutdown Mode (LT6023-1)
  • 8-Lead MSOP & 3 × 3 mm DFN Packages

Fully specified over the –40°C to 85°C and –40°C to 125°C temperature ranges, the LT6023 is available in MSOP-8 and 3 × 3 mm DFN packages. Prices start at $1.85 each in quantities of 1,000 units.

Source: Linear Technology

CAN Flexible Data-Rate Transceiver Family

Microchip Technology recently launched the MCP2561/2FD family of CAN Flexible Data-Rate (FD) transceivers. As an interface between a CAN controller and the physical two-wire CAN bus, the transceivers work for both the CAN and CAN FD protocols. Thus, the family helps automotive and industrial manufacturers with current CAN communication needs and provides a path for newer CAN FD networks.Microchip MCP25612FD CAN FD transceivers

In-vehicle networking growth continues to be driven by the need for electronic monitoring and control. As application features in power train, body and convenience, diagnostics and safety increase, more Electronic Control Units (ECUs) are being added to existing CAN buses, causing automotive OEMs to become bandwidth limited. In addition, the end-of-line programming time for ECUs is on the rise due to more complex application programs and calibration, which raises production line costs. The emerging CAN FD bus protocol solves these issues by increasing the maximum data rate while expanding the data field from 8 data bytes up to 64 data bytes.

With their robustness and industry-leading features, including data rates of up to 8 Mbps, Microchip’s MCP2561/2FD transceivers enable customers to implement and realize the benefits of CAN FD. These new transceivers have one of the industry’s lowest standby current consumption (less than 5 µA typical), helping meet ECU low-power budget requirements. Additionally, these devices support operation in the –40°C to 150°C temperature range, enabling usage in harsh environments.

The new family of MCP2561/2FD CAN FD transceivers is available in eight-pin PDIP, SOIC and 3 × 3 mm DFN (leadless) packages, providing additional design flexibility for space-limited applications. The family also provides two options. The MCP2561FD comes in an 8-pin package and features a SPLIT pin. This SPLIT pin helps to stabilize the common mode in biased split-termination schemes. The MCP2562FD is available in an eight-pin package and features a Vio pin. This Vio pin can be tied to a secondary supply in order to internally level shift the digital I/Os for easy microcontroller interfacing. This is beneficial when a system is using a microcontroller at a VDD less than 5 V (e.g., 1.8 V or 3.3 V), and eliminates the need for an external level translator, decreasing system cost and complexity.

The MCP2561FD and MCP2562FD transceivers are both available now for sampling and volume production in 8-pin PDIP, SOIC and 3 × 3 mm DFN packages, starting at $0.69 each, in 5,000-unit quantities.

Source: Microchip Technology

Microcontroller-Based Sentry System

David Penrose’s “Sentry” project comprises an array of passive IR sensors placed throughout a building to track motion. The microcontroller-based system comprises an RF link to a processor along with an Ethernet module to unobtrusively monitor motion and activity levels.

The Sentry system uses commercial IR motion sensors (lower left) together with a customer vibration sensor (lower right) to determine where an individual is within a building. The base unit (top) integrates reports from these sensors to generate alerts to a caregiver.

Photo 1: The Sentry system uses commercial IR motion sensors (lower left) together with a customer vibration sensor (lower right) to determine where an individual is within a building. The base unit (top) integrates reports from these sensors to generate alerts to a caregiver.

Penrose writes:

My Sentry System is designed to assist those folks living alone who desire the peace of mind provided by a caregiver looking after them without the caregiver having to be present. Its implementation was facilitated by the WIZnet WIZ550io Ethernet module, which provides a rich yet simple interface to the Internet. With a simple microprocessor, the system allows the status of a resident to be continuously monitored in a minimally intrusive fashion.

Any abnormal conditions can immediately be alerted to a remote caregiver for action. In this way, a caregiver’s smartphone acts as an alert system by letting them know when a resident’s activity deviates from a normal pattern. The system is designed to be simple to set up yet very flexible in its application so the needs of different residents can be addressed. A resident with minimal needs can be monitored by a set of relaxed rules, while a resident in need of more continuous observation can be assigned a set of strict rules. In all cases, the overarching design approach was to provide a system that augments the caregiver’s capability.

Penrose goes on to describe the system:

The Sentry System integrates motion sensors, a microprocessor, and the WIZ550io Ethernet interface to monitor a resident and report abnormal activity patterns to a remote caregiver (see Photo 1). The relationship of these subsystems is illustrated in Figure 1.

Up to eight sensors transmit activity to a base unit processor, which checks for abnormal behavior of a resident. Alerts to a caregiver are generated and communicated over the Internet.

Figure 1: Up to eight sensors transmit activity to a base unit processor, which checks for abnormal behavior of a resident. Alerts to a caregiver are generated and communicated over the Internet.

The primary sensors are IR motion sensors. These can be augmented by vibration sensors, pressure mats, ultrasonic, and other devices capable of detecting a person’s presence. These sensors are placed at key locations in a resident’s home to monitor movement from room to room or within rooms. The vibration sensors are placed in favorite chairs/couches or in the bed to determine if the furniture is occupied and if there is normal activity. All of these sensors are battery powered and report over an RF link. The RF reports from these devices are received by a base unit which then compares the resident’s location and activity to a set of rules that define normal behavior for different times of day. Any deviation from normal results in an SMS text message or e-mail being sent to the caregiver along with information about how to contact the resident. In most cases, it is expected that the caregiver would respond by phoning the resident to check on them.

The system is designed to be easy to install and operate. The WIZ550io’s Internet interface is used to communicate to a browser allowing the caregiver or resident to configure the system. This configuration consists of identifying sensors and rooms and describing a set of rules for each room for periods in the day. This local interface also allows for a review of all past activity once the system is operational. This history data is valuable for refining the rules to reduce false alarms and ensure security. Since the interface is behind the resident’s firewall, the system is secure from improper modification. The key output from the system is the alert to the caregiver, which relies on the WIZ550io module communicating to a service site such as Exosite. The site generates the alerts sent to the caregiver.

The base unit incorporates the WIZ550io, an 89LPC936 processor, a MCP79401 real-time clock, and a serial EEPROM to process reports received from the 433-MHz receiver.

Photo 2: The base unit incorporates the WIZ550io, an 89LPC936 processor, a MCP79401 real-time clock, and a serial EEPROM to process reports received from the 433-MHz receiver.

The system’s hardware consists of a base unit and multiple sensor/reporting units. The base unit (see Photo 2) comprises a WIZ550io Ethernet interface, an inexpensive microprocessor, an RF receiver, a battery backed-up real-time clock, and a serial EEPROM. All of these pieces are integrated into a small form factor case and powered by a plug-in transformer (see Figure 2).

Figure 2: The microprocessor accomplishes all of its tasks while using only a few of the available port pins.

Figure 2: The microprocessor accomplishes all of its tasks while using only a few of the available port pins.

The remote units can be one of many different sensor/reporting devices depending on the needs of the resident. The basic sensor is the IR motion sensor, which is available from a number of different sources.  I used Bunker Hill Security sensors, which I purchased from Harbor Freight Tools (Item 93068). A sensor plus receiver is very inexpensive. Some cost only $11. The item consists of a sensor/transmitter and a receiver/alarm device. The receiver/alarm device is not used in this project although the RF receiver was lifted from one of these units to provide the receiver for the base unit. These sensor units are powered by 9-V batteries and report on an RF link at 433 MHz with a unique address code.  The code allows multiple sensors to be deployed and recognized by the base unit.

The complete article appears in Circuit Cellar 296 (March 2015).

5-V Qi Low-Power Wireless Charging Transmitter Reference Design

NXP Semiconductors has announced the availability of a new reference design for 5-V low-power Qi wireless charging transmitters, compliant with the Wireless Power Consortium (WPC) 1.1 Qi specification. The design is based on NXPs single-chip 5-V wireless power transmitter IC—the NXQ1TXA5 that was launched in 2014. It is the latest addition to NXP’s portfolio of Greenchip power solutions.NXP NXQ1TXA5

Building on NXP’s success as the market leader in Greenchip power ICs, the NXQ1TXA5 reference design has an unrivalled standby power consumption of less than 10 mW. It is the only solution on the market today that meets five-star mobile phone charger standby power ratings by consuming less than 30 mW in standby mode, which includes the standby power of the wall-charger. NXP recommends combining its NXQ1TXA5 ultra low standby power wireless power transmitter solution with another Greenchip device, its high efficiency TEA1720 SMPS IC with a standby power of less than 20 mW.

The NXQ1TXA5 device combines:

  • NXPs patented high efficiency Class D amplifier technology for outstanding EMI performance.
  • NXP’s ultra low power CoolFluxTM DSP technology for superior communication with smartphones placed on the charger.
  • Dedicated low power mixed signal circuitry to check for smartphone presence three times per second, enabling fast startup of charging, while keeping the standby power very low if there is no smartphone on the charger.

Due to the NXQ1TXA5’s  low-power consumption, the reference design also has a high efficiency for low transmitted powers, making it suitable for applications ranging from smartphone charging to deliver 5 W to the smartphone battery when used with a Qi compliant wireless charging receiver, to chargers for wearables that need less than 2-W charging power.

The NXQ1TXA5 reference design needs only 15 to 20 low-cost passive components and uses a standard two-layer PCB, with the components mounted on a single side. Depending on customer requirements, the complete application can be designed on a board space as small as 3 × 3 or 4 × 4 cm.

The new NXQ1TXA5 wireless charging transmitter reference design will be available in Q2.

Source: NXP Semiconductors

5-GHz Power Amplifier Module for WLAN Applications

Microchip Technology has announced a new SST11CP22 5-GHz power amplifier module (PAM) for the IEEE 802.11ac ultra high data rate Wi-Fi standard. This PAM delivers 19-dBm linear output power at 1.8% dynamic Error Vector Magnitude (EVM) with MCS9 80-MHz bandwidth modulation. The SST11CP22 delivers 20-dBm linear power at 3% EVM for 802.11a/n applications. It is spectrum mask compliant up to 24 dBm for 802.11a communication, and it has less than –45-dBm/MHz RF harmonic output at this output power, making it easier for the system board to meet FCC regulations.Microchip SST11CP22

Achieving the maximum data rate and longest range while minimizing current consumption is essential to Wi-Fi MIMO access-point, router and set-top-box system designers. The SST11CP22’s low EVM and high linear power facilitate MIMO operation and significantly extend the range of 802.11ac systems in ultra-high data rate transmission mode. The module, housed in a space-saving 4 × 4 mm, 20-pin QFN package, includes an output harmonic rejection filter and is 50 Ohm-matched—requiring only four external components. It is easy to use and reduces board size. Additionally, the integrated linear power detector provides accurate output power control over temperature and 2-to-1 output mismatch. These features are critical for 802.11ac Wi-Fi set-top boxes, routers, access points, and wireless video streaming devices that operate at high data rates.

Developers can begin designing today with the SST11CP22 Evaluation Board (SST11CP22-GN-K). The SST11CP22 RF Power Amplifier Module is available in a 4 × 4 mm, 20-pin QFN package for $0.92 each in 10,000-unit quantities. Sampling and volume production are both available now.

Source: Microchip Technology

OptiMOS Product Family Exceeds 95% Efficiency

Infineon Technologies recently launched the OptiMOS 5 25- and 30-V product family, the next generation of Power MOSFETs in standard discrete packages, a new class of power stages named Power Block, and in an integrated power stage, DrMOS 5×5. Together with Infineon’s driver and digital controller products the company delivers full system solutions for applications such as server, client, datacom or telecom.Infineon-OptiMOS

The newly introduced OptiMOS family offers benchmark solutions with efficiency improvements of around 1% across the whole load range compared to its previous generation, exceeding 95% peak efficiency in a typical server voltage regulator design. This improved performance is based for example on the reduction of switching losses (Q switch) by 50% compared to the previous OptiMOS technology. Thus, implementing the new OptiMOS 25 V would lead to energy savings of 26.3 kWh per year for a single 130-W server CPU working 365 days.

The launch of the OptiMOS product family is accompanied by the introduction of a new packaging technology offering a further reduction in PCB area consumption. It is used in the Power Block product family and in the integrated powerstage DrMOS 5×5 and offers a source down low-side MOSFET for improved thermal performance, with a reduction by 50% of the thermal resistance in comparison to standard package solution, such as SuperSO8.

Infineon`s Power Block is a leadless SMD package comprising the low-side and high-side MOSFET of a synchronous DC/DC converter into a 5.0 × 6.0 mm 2 package outline. With Power Block, customers can shrink their designs up to 85 percent by replacing two separate discrete packages, such as SuperSO8 or SO-8. Both, the small package outline and the interconnection of the two MOSFETs within the package minimize the loop inductance for best system performance.

OptiMOS 5 25V is also used in an integrated power stage, combining DrMOS 5×5, driver and two MOSFETs, for a total area consumption on the PCB equal to 25mm². The integrated driver plus MOSFETs solution results in a shorter design time and is easy to design-in. Additionally, the dovetailed power stage includes a high accurate temperature sense of +/-5°C (compared to +/-10°C of an external one) which enables higher system reliability and performance.

Samples of the new OptiMOS 25- and 30-V devices in SuperSO8, S3O8 and Power Block packages, with on-state resistances from 0.9 mΩ to 3.3 mΩ are available. Additional products with monolithic integrated Schottky-like diode and products in 30 V will be available from Q2 2015 onwards. DrMOS 5×5 will be released in Q2 2015. Samples are available.

Source: Infineon