NXP LPC800 Microcontroller Challenge

Attention microcontroller users around the world! Ready to enter NXP Semiconductor’s LPC800 Challenge? Getting started is straightforward.

Elektor and Circuit Cellar have partnered with NXP Semiconductors to promote the Challenge. Once you have your LPC800 mini-board and code, you simply register and start working. The rules and complete details are listed on the LPC800 Challenge webpage.

The entry deadline is August 30, 2013. Once all the entries are received, NXP will select the most unique, interesting and funny submissions to receive a LPC800 LPCXpresso development kit.

The LPC800 is an ARM Cortex-M0+-based, 32-bit microcontroller operating at CPU frequencies of up to 30 MHz. The LPC800 supports up to 16 KB of flash memory and 4 KB of SRAM. The peripheral complement of the LPC800 includes a CRC engine, one I2C-bus interface, three USARTs, two SPI interfaces, one multi-purpose, state-configurable timer, one comparator, function-configurable I/O ports through a switch matrix, and up to 18 general purpose I/O pins.

Need design ideas? Check out these microcontroller projects with NXP parts.

Elektor’s Electronics Lab

Want to share electronics projects? Looking for a design community that will help you reach your project goals? Need feedback on your electronic system-related ideas, applications, and design plans?

ELektor.LABS is for you!

Current projects in Elektor.LABS:

  • PLµX: Programmable Logic Microcontroller on Linux
  • Wireless Batter Charger
  • LPC810 as NE555 or as Capacitance Meter
  • FPGA Development Board
  • USB-IO24 Cable
  • Wi-Fi RGB LED Strip
  • And many more!

Want to know more? Check out this video.

CircuitCellar.com is an Elektor International Media publication.

SMD Stencil Reflow Soldering Tutorial

Surface-mount SMD reflow soldering doesn’t have to be difficult. All you need is a solder paste stencil, a hot air gun, and a little know-how. No reflow oven necessary!

Dave Jones, of EEVblog.com, covers everything you need to know in the following easy-to-understand SMD stencil reflow soldering tutorial.

The kit is available via Elektor’s partner, Eurocircuits.

The Eurocircuits kit includes all the essential SMT components, circuit boards, and solder stencils.

For SMT info and additional projects, refer to Vincent Himpe’s book, Mastering Surface Mount Technology (Elektor).

CircuitCellar.com is an Elektor International Media website.

RS Components + Elektor = DesignSpark Magazine

RS Components has announced the launch of its new online publication, DesignSpark Magazine. The new magazine will be published in collaboration with Elektor International Media, the global electronics design and publishing house that publishes Elektor, Circuit Cellar, audioXpress, and more.

DesignSpark Magazine will replace RS Components’s popular eTech Magazine, which was first released as a digital edition in July 2010. According to a statement released by RS Components, “The new title is available as a fully digital publication in iPad, iPhone, Android tablet and page-turner formats. The publishing partnership with Elektor will produce not only a fresh-look magazine, but in addition will draw on Elektor’s long experience in the electronics publishing field to deliver the highest quality of technical content as a source of inspiration for design engineers worldwide.”

DesignSpark Magazine, which derives its name from designspark.com, the RS online community for electronics design engineers, will address three key topic areas:

  • Technologies – This will feature the best boards and board-level components for engineers and give readers a snapshot of the newest hot products in the market.
  • Software and tools – Keeping readers in touch with the latest resources to save time and money, this area will focus on free tools to support engineers.
  • Projects – Inspired by positive feedback on project-style articles in eTech, this expanded section in the new magazine will feature more design-tips articles contributed by Elektor, as well as make-and-build projects from the DesignSpark community. Readers will have access to the information located in this section to develop their own projects.

The new publication is designed to appeal to readers across the globe, with the concurrent launch of eight different language versions: English; Dutch; French; German; Italian; Japanese; Simplified Chinese and Spanish.

Mark Cundle, Head of Technical Marketing at RS, commented, “The RS online DesignSpark community has become a respected and well-used source of information and tools for electronics engineers over the past few years, so it is a natural progression to align the name of our proprietary online publication with the DesignSpark brand. The magazine is an integral part of our efforts to provide customers with a trusted, reliable source of technical information to help reduce design times and costs.”

Wisse Hettinga, International Director for Elektor International Media, said, “This exciting collaboration with RS Components will be good news for everyone who is an enthusiast and active in electronics design. It will mean more designs, more inspiration, more ‘how to’ and ‘where to get’ information to speed up the design process and create new, interesting electronic products.”

[Via Electrocomponents.com]

CircuitCellar.com is an Elektor International Media website.

Microcontroller-Based Heating System Monitor

Checking a heating system’s consumption is simple enough.

Heating system monitor

Determining a heating system’s output can be much more difficult, unless you have this nifty design. This Atmel ATmega microcontroller-based project enables you to measure heat output as well as control a circulation pump.

Heating bills often present unpleasant surprises. Despite your best efforts to economise on heating, they list tidy sums for electricity or gas consumption. In this article we describe a relatively easy way to check these values and monitor your consumption almost continuously. All you need in order to determine how much heat your system delivers is four temperature sensors, a bit of wiring, and a microcontroller. There’s no need to delve into the electrical or hydraulic components of your system or modify any of them.

A bit of theory
As many readers probably remember from their physics lessons, it’s easy to calculate the amount of heat transferred to a medium such as water. It is given by the product of the temperature change ΔT, the volume V of the medium, and the specific heat capacity CV of the medium. The power P, which is amount of energy transferred per unit time, is:

P= ΔT × CV × V // Δt

With a fluid medium, the term V // Δt can be interpreted as a volumetric flow Vt. This value can be calculated directly from the flow velocity v of the medium and the inner diameter r of the pipe. In a central heating system, the temperature difference ΔT is simply the difference between the supply (S) and return (R) temperatures. This yields the formula:

P = (TS – TR) × CV × v × pr2

The temperatures can easily be measured with suitable sensors. Flow transducers are available for measuring the flow velocity, but installing a flow transducer always requires drilling a hole in a pipe or opening up the piping to insert a fitting.

Measuring principle
Here we used a different method to determine the flow velocity. We make use of the fact that the supply and return temperatures always vary by at least one to two degrees due to the operation of the control system. If pairs of temperature sensors separated by a few metres are mounted on the supply and return lines, the flow velocity can be determined from the time offset of the variations measured by the two sensors…

As the water flows through the pipe with a speed of only a few metres per second, the temperature at sensor position S2 rises somewhat later than the temperature at sensor position S, which is closer to the boiler.

An ATmega microcontroller constantly acquires temperature data from the two sensors. The time delay between the signals from a pair of sensors is determined by a correlation algorithm in the signal processing software, which shifts the signal waveforms from the two supply line sensors relative to each other until they virtually overlap.The temperature signals from the sensors on the return line are correlated in the same manner, and ideally the time offsets obtained for the supply and return lines should be the same.

To increase the sensitivity of the system, the return line sensor signals are applied to the inputs of a differential amplifier, and the resulting difference signal is amplified. This difference signal is also logged as a function of time. The area under the curve of the difference signal is a measure of the time offset of the temperature variations…

Hot water please
If the heating system is also used to supply hot water for domestic use, additional pipes are used for this purpose. For this reason, the PCB designed by the author includes inputs for additional temperature sensors. It also has a switched output for driving a relay that can control a circulation pump.

Under certain conditions, controlling the circulation pump can save you a lot of money and significantly reduce CO2 emissions. This is because some systems have constant hot water circulation so users can draw hot water from the tap immediately. This costs electricity to power the pump, and energy is also lost through the pipe walls. This can be remedied by the author’s circuit, which switches on the circulation pump for only a short time after the hot water tap is opened. This is detected by the temperature difference between the hot water and cold water supply lines…

Circuit description
The easiest way to understand the schematic diagram is to follow the signal path. It starts at the temperature sensors connected to the circuit board, which are NTC silicon devices.

Heating system monitor schematic

Their resistance varies by around 0.7–0.8% per degree K change in temperature. For example, the resistance of a KT110 sensor is approximately 1.7 kΩ at 5 °C and approximately 2.8 kΩ at 70 °C.

The sensor for supply temperature S forms a voltage divider with resistor R37. This is followed by a simple low-pass filter formed by R36 and C20, which filters out induced AC hum. U4a amplifies the sensor signal by a factor of approximately 8. The TL2264 used here is a rail-to-rail opamp, so the output voltage can assume almost any value within the supply voltage range. This increases the absolute measurement accuracy, since the full output signal amplitude is used. U4a naturally needs a reference voltage on its inverting input. This is provided by the combination of R20, R26 and R27. U5b acts as an impedance converter to minimise the load on the voltage divider…

Thermal power

PC connection
The circuit does not have its own display unit, but instead delivers its readings to a PC via an RS485 bus. Its functions can also be controlled from the PC. IC U8 looks after signal level conversion between the TTL transmit and receive lines of the ATmega microcontroller’s integrated UART and the differential RS485 bus. As the bus protocol allows several connected (peer) devices to transmit data on the bus, transmit mode must be selected actively via pin 3. Jumper JP3 must be fitted if the circuit is connected to the end of the RS485 bus. This causes the bus to be terminated in 120 Ω, which matches the characteristic impedance of a twisted-pair line…

[Via Elektor-Projects.com]