introduction with block diagram for function generator

A function generator is a signal source that has the capability of producing different types of waveforms as its output signal. The most common output waveforms are sine-waves, triangular waves, square waves, and sawtooth waves. The frequencies of such waveforms may be adjusted from a fraction of a hertz to several hundred kHz.

Actually the function generators are very versatile instruments as they are capable of producing a wide variety of waveforms and frequencies. In fact, each of the waveform they generate are particularly suitable for a different group of applications. The uses of sinusoidal outputs and square-wave outputs have already been described in the earlier Arts. The triangular-wave and sawtooth wave outputs of function generators are commonly used for those applications which need a signal that increases (or reduces) at a specific linear rate. They are also used in driving sweep oscillators in oscilloscopes and the X-axis of X-Y recorders.

Many function generators are also capable of generating two different waveforms simultaneously (from different output terminals, of course). This can be a useful feature when two generated signals are required for particular application. For instance, by provid­ing a square wave for linearity measurements in an audio-system, a simultaneous sawtooth output may be used to drive the horizontal deflection amplifier of an oscilloscope, providing a visual display of the measurement result. For another example, a triangular-wave and a sine-wave of equal frequencies can be produced simultaneously. If the zero crossings of both the waves are made to occur at the same time, a linearly varying waveform is available which can be started at the point of zero phase of a sine-wave.

Another important feature of some function generators is their capability of phase-locking to an external signal source. One function generator may be used to phase lock a second function generator, and the two output signals can be displaced in phase by an adjustable amount. In addition, one function generator may be phase locked to a harmonic of the sine-wave of another function generator. By adjustment of the phase and the amplitude of the

harmonics, almost any waveform may be produced by the summation of the fundamental frequency generated by one function generator and the harmonic generated by the other function generator. The function generator can also be phase locked to an accurate fre­quency standard, and all its output waveforms will have the same frequency, stability, and accuracy as the standard.

The block diagram of a function generator is given in figure. In this instrument the frequency is controlled by varying the magnitude of current that drives the integrator. This instrument provides different types of waveforms (such as sinusoidal, triangular and square waves) as its output signal with a frequency range of 0.01 Hz to 100 kHz.

The frequency controlled voltage regulates two current supply sources. Current supply source 1 supplies constant current to the integrator whose output voltage rises linearly with time. An increase or decrease in the current increases or reduces the slope of the output voltage and thus controls the frequency.

The voltage comparator multivibrator changes state at a predetermined maximum level, of the integrator output voltage. This change cuts-off the current supply from supply source 1 and switches to the supply source 2. The current supply source 2 supplies a reverse current to the integrator so that its output drops linearly with time. When the output attains a pre­determined level, the voltage comparator again changes state and switches on to the current supply source. The output of the integrator is a triangular wave whose frequency depends on the current supplied by the constant current supply sources. The comparator output provides a square wave of the same frequency as output. The resistance diode network changes the slope of the triangular wave as its amplitude changes and produces a sinusoidal wave with less than 1% distortion.

S:circuitstoday.com

programmable unijunction transistor (PUT) controlled sawtooth generator circuit

A PUT controlled sawtooth generator circuit is shown in figure. When power is first applied, the programmable unijunction transistor (PUT) is off. The capacitor C begins to charge up and the output voltage rises. This continues until the output voltage (which is also the PUT anode voltage) is about 0.7 V above the control input (the gate voltage). The PUT gets switched on. The capacitor C is shorted out through PUT and, therefore, capacitor gets immediately dis­charged through the PUT. The output voltage, which is equal to the voltage across the capacitor, falls. When the current through the PUT falls below its holding current I_H, it goes off and the cycle repeats. When the PUT turns off, approximately 1 V is usually left on the capacitor. The output waveform is shown in figure.

The time period of the PUT controlled sawtooth generator depends on the charge rate (V/RC) and the control voltage V_control. This is obvious from figure.

Time period, T = Distance / Rate = (V_control + 0.7 V) – 1V / (І-V І/RC)

= V_control RC / І-V І………………. {І-V І = magnitude of –V}

and frequency, f = 1/T = І-V І/V_control RC

The PUT controlled sawtooth generator can be used as a voltage-to-frequency converter.

Precautions

• The cathode of the PUT must be tied to ground or virtual ground and current flows only from anode to cathode. So PUT cannot be used to control a negative ramp generator.
• To turn-off the current through the PUT must drop below its holding current I_H (specified by the manufacturer). When the PUT is on, a current equal to that used to charge the capacitor, in addition to capacitor discharge current, flows through the PUT. This current flows through R to V^- must be below I_H.

That is, I = V/R < I_H

Failing which, once the PUT goes on, it will be held on by this charge current, even when the capacitor has fully discharged. This charge current can be lowered by increasing R or reducing negative voltage V^-.. However, both of these factors affect the change rate and. Therefore, the frequency. For keeping frequency unaffected the changes in either R or V^- will have to be balanced with appropriate changes in C.

How to make a Schmitt trigger or a Regenerative Comparator using 741 IC ?

A Schmitt trigger circuit is a fast-operating voltage-level detector. When the input voltage arrives at the upper or lower trigger levels, the output changes rapidly. The circuit operates with almost any type of input waveform, and it gives a pulse-type output.

The circuit of an op-amp Schmitt trigger circuit is shown in figure. The input voltage v_in is applied to the inverting input terminal and the feedback voltage goes to the non-inverting terminal. This means the circuit uses positive voltage feedback instead of negative feedback, that is, in this circuit feedback voltage aids the input voltage rather than opposing it. For instance, assume the inverting input voltage to be slightly positive. This will produce a negative output voltage. The voltage divider feedsback a negative voltage to the non-inverting input, which results in a larger negative voltage. This feedsback more nega­tive voltage until the circuit is driven into negative saturation. If the input voltage were, slightly negative instead of positive, the circuit would be driven into the positive saturation. This is the reason the circuit is also referred to as re­generative comparator.

When the circuit is positively saturated, a positive voltage is fedback to the non-in­verting input. This positive input holds the output in the high state. Similarly, when the output voltage is negatively saturated, anegative voltage is fedback to the non-inverting input, holding the output in the low state. In either case, the positive feedback reinforces the existing output state.

The feedback fraction, β = R₂/R₁ + R₂

When the output is positively saturated, the reference voltage applied to the non-inverting input is

V_ref ^{= +} βV_sat

When the output is negatively saturated, the reference voltage is

V_ref ^{= -} βV_sat

The output voltage will remain in a given state until the input voltage exceeds the reference voltage for that state. For instance, if the output is positively saturated, the reference voltage is + βV_sat. The input voltage v_in must be increased slightly above + β V_sat to switch the output voltage from positive to negative, as shown in figure. Once the output is in the negative state, it will remain there indefinitely until the input voltage becomes more negative than – βV_sat. Then the output switches from negative to positive. This can be explained from the input-output characteristics of the Schmitt trigger shown in figure, as below.

Characteristics of the Schmitt trigger

Assume that input voltage v_in is greater than the + β V_sat, and output voltage v_OUT is at its negative extreme (point 1). The voltage across R₂ in the figure is a negative quantity.

As a result, v_in must be reduced to this negative voltage level (point 2 on the characteristics) before the output switches positively (point 3). If the input voltage is made more negative than the – β V_sat, the output remains at + +v_OUT (points 3 to 4). For the output to go negative once again, v_in must be increased to the + β V_sat level (point 5 on the characteristics).

In figure, the trip points are defined as the two input voltages where the output changes states. The upper trip point (abbreviated UTP) has a value

UTP = β V_sat and the lower trip point has a value

LTP = – β V_sat

The difference between the trip points is the hysteresis H and is given as

H = + β V_sat – (-β V_sat) = 2 β V_sat

The hysteresis is caused due to positive feedback. If there were no positive feedback, β would equal zero and the hysteresis would disappear, because the trip points would both equal zero.

Hysteresis is desirable in a Schmitt trigger because it prevents noise form causing false triggering.

To design a Schmitt trigger, potential divider current I₂ is once again selected to be very much larger than the op-amp input bias current. Then the resistor R₂ is calculated from equation

R₂ = UTP/I₂

and R₁ is determined from

R_{1 =} (V_OUT – UTP) / I₂

S:circuitstoday.com

example of a relaxation oscillator(The op-amp triangular-wave generator)

The op-amp triangular-wave generator is another example of a relaxation oscillator. We know that the integrator output waveform will be triangular if the input to it is a square-wave. It means that a triangular-wave generator can be formed by simply cascading an integrator and a square-wave generator, as illustrated in figure. This circuit needs a dual op-amp, two capacitors, and at least five resistors. The rectangular-wave output of the square-wave generator drives the integrator which produces a triangular output waveform. The rectangular-wave swings between +V_sat and -V_sat with a time period determined from equation. The triangular-waveform has the same period and frequency as the square-waveform. Peak to-peak value of output triangular-waveform can be obtained from the following equation.

The input of integrator A₂ is a square wave and its output is a triangular waveform, the output of integrator will be triangular wave only when R₄ C₂ > T/ 2 where T is the ( period of square wave. As a general rule, R₄C₂ should be equal to T. It may also be necessary to shunt the capacitor C₂ with resistance R₅ = 10 R₄ and connect an offset volt compensating network at the non-inverting (+) input terminal of op-amp A₂ so as to obtain a stable triangular wave. Since the frequency of the triangular-wave generator like any other oscillator, is limited by the op-amp slew-rate, a high slew rate op-amp, like LM 301, should be used for the generation of relatively higher frequency waveforms.

S:circuitstoday.com

How to make a Sawtooth Wave Generator using Op-Amp 741 IC?

Sometimes it is felt necessary to provide a relatively slow linear ramp with a rapid fall (or rise in the case of a negative ramp) at its end. This is a sawtooth wave. Also, in applications such as time base generators and power control circuits, the sawtooth must be triggered by (or be synchronized with) some control signal.

The difference between the triangular and sawtooth waveforms is that in triangular waves the rise time is always equal to its fall time while the sawtooth waveforms have different rise and fall times i.e. sawtooth wave may rise positively many times faster than it falls negatively or vice-versa.

The circuit shown in figure provides the ability of controlling ramp generation with an external signal. In the circuit shown, an NPN BJT has been placed around the charging capacitor C and emitter of the transistor is tied to the inverting (-) terminal of the op-amp, which is at virtual ground. Resistor R_B is for limiting the base current and so for protecting the BJT. However, R_B is to be kept rela­tively small to assure that the transistor can be driven into saturation.

With a zero or negative control input voltage, the transistor is off. The capacitor charges up from the op-amp output, through C, R_in and to V-. The charge rate is given as

Rate = V- / R_in *C

If the control voltage is not changed, the capacitor C will eventually charge up, and hold the output at + V_sat.

However, when a positive control input is applied, the transistor gets turned on. If this voltage is large enough to force transistor into satu­ration the capacitor is effectively short- circuited. The capacitor C rapidly dis­charges.

The output voltage falls to zero (actually about 0.2 V) and stays there as long as positive control voltage keeps the transistor saturated. The expected obtainable waveform is given in figure. For control of negative going ramps, the circuit shown in figure will require several minor changes. First, the charging voltage, connected to R_in, polarity will have to be reversed to V+. This reverses the direction of charging current. It means capacitor will also have to reversed, if it is electrolytic one. The emitter of the transistor must be connected to virtual ground (the inverting input terminal of op-amp). To allow the capacitor to discharge from left to right, NPN transistor would have to be replaced by PNP transistor. In this case, a zero or positive control input would keep the PNP transistor off, while a negative control input would be required to turn the transistor on.

Dual Output 20-V, 3-A Switching Regulator Features High and Flat Conversion Efficiency

Analog Devices introduced the ADP2323, a 20-V, 3-A dual output DC-to-DC regulator featuring a high conversion efficiency of greater than 93 percent. The full featured ADP2323 regulator offers an input voltage supply range of 4.5 V to 20 V and an output range as low as 0.6 V up to 18 V at 1.5 percent voltage accuracy. With more design flexibility and configurability than other DC-to-DC regulators available today, the ADP2323 regulator can be easily configured to synchronise in an evenly phase-shifted topology or for dual-output (2 x 3A) or single interleaved output (up to 6 A). The ADP2323 provides accurate tracking capability between supplies and includes precision-enable input, voltage tracking input and POWER-GOOD features that allow a simple and reliable start-up sequence.

For power designers who need higher efficiency more design flexibility and configurability for multi-rail applications, the ADP2323 surpasses other available DC-to-DC regulators,” said Evaldo Miranda, product line director, Power Management Products Group, Analog Devices. “Unlike other regulators, the ADP2323 enables six output rails in an evenly phase-shifted topology, minimising input current ripple and system interference as well as a power saving mode and current sharing for higher output current capability.

The ADP2323’s switching frequency can be programmed between 250 kHz to 1.2 MHz or synchronised to an external clock to minimise interference in multi-rail applications. Both output channels run 180 degrees out of phase and can be synchronised to eliminate beat frequencies between regulators to minimise system noise. The regulator operates from input voltages of 4.5 V to 20 V and the output voltage can be as low as 0.6 V. The two PWM channels can be configured to deliver dual 3-A outputs or a parallel-to-single 6-A output. Designed for high efficiency for multi-rail applications, the ADP2323 operates over the −40 °C to +125 °C junction temperature range and is available in a compact 5 mm x 5 mm QFN-32 lead package.

Features

• Input voltage 4.5 V to 20 V
• ±1% output accuracy
• Integrated 90 mΩ typical high-side MOSFET
• Flexible output configuration
  • Dual output: 3 A/3 A
  • Parallel single output: 6 A
• Programmable switching frequency: 250 kHz to 1.2 MHz
• External synchronization input with programmable phase shift, or internal clock output
• Selectable PWM or PFM mode operation
• Adjustable current limit for small inductor
• External compensation and soft start
• Startup into precharged output

Applications

• Communication infrastructure
• Networking and servers
• Industrial and instrumentation
• Healthcare and medical
• Intermediate power rail conversion
• DC-to-dc point of load applications

analog.com

ZMDI introduces 98% energy efficient LED driver IC for Retrofit LED lamps and low manufacturing cost

ZMD AG has announced availability of the ZLED7320, a new member of its high current ZLED7x20 family of 40V LED-Driver-ICs. The ZLED7320, which operates at up to 98% efficiency and is available in a small-footprint DFN-5 package, is designed to help manufacturer’s cost-effectively address the growing high-brightness (HB) LED lighting market.

“The ZLED7320 bridges the gap between our existing 0.75A and 1.2A high-efficiency drivers while the small-footprint package provides easier assembly” stated Dr. Hendrik Ahlendorf, Product Manager at ZMDI. “The ZLED7320 provides an ideal solution for many cost- and size- sensitive applications, including Retrofit LED lamps, signage, street and traffic lights, spotlights, appliance lighting and all types of general home and office illumination”.

The LED driver features on-chip switching transistor, 1200:1 dimming via PWM signal or fixed voltage, up to 1 amps of output current at +/- 3% accuracy and high-side current sensing. Built-in protection includes thermal shutdown, open-circuit and short-circuit protection. Due to its output current capabilities, the ZLED7320 supports the new high brightness and high current LEDs from major LED manufacturers without requiring an additional MOSFET to the application circuit. Only the addition of 4 passive components is required for a complete LED driver solution. The device operates at a temperature range of -40°C to 105°C.

The DFN-5 package simplifies board assembly and offers improved packing density for area- or volume- constrained systems. Thanks to its compact size, manufacturers can develop innovative new products and applications where efficient high-brightness LED solutions are a market advantage.

The ZLED7320 is in full production now and a complete evaluation kit is available from the company. For 2,500 pieces, the ZLED7320 is priced at 0.66€ or US$0.86.

ZMDI has also introduced the ZLED7330, a high-current 40V LED driver with user selectable switch dimming suitable for high brightness LED lighting applications and the ZLED7002, a dual channel LED Driver with supply voltage switchable channel toggling suitable for extended-life battery operated portable LED lighting applications. Both the ZLED7330 and the ZLED7002 are in full production and complete evaluation kits are available. For 2,500 pieces, the ZLED7330 is priced at 1.06€ or US$1.38 and the ZLED7002 is priced at 0.47€ or US$0.62.

Typical ZLED7x20 application circuit:

zmdi.com

High current, energy efficient MOSFETs in the SOT-23F package

Central Semiconductor's CMPDM203NH (N-Channel) and CMPDM202PH (P-Channel) are Enhancement mode MOSFETs in industry standard SOT-23F packages that optimize high current capability and energy efficiency. The combination of high current, low gate charge and low on-resistance makes these devices the ideal selection for energy sensitive applications requiring higher drain currents.

Features

• Low r_DS(ON):
  • (0.033Ω @ V_GS=4.5V) N-Channel
  • (0.064Ω @ V_GS=5.0V) P-Channel
• High current I_D:
  • 3.2A (N-Channel)
  • 2.3A (P-Channel)
• Low gate charge Q_gs:
  • 0.8nC (N-Channel)
  • 1.3nC (P-Channel)

Applications

• Load/Power switches
• Power supply converter circuits
• Battery powered portable equipment
• Motor control

Benefits

• Energy efficiency
• 9% lower package profile than the SOT-23
• Fast switching speed t_on:
  • 6.0ns (N-Channel)
  • 15.2ns (P-Channel)

centralsemi.com

TI - Industry's smallest, fully integrated 16-bit ADC

Texas Instruments has introduced the industry's smallest, 16-bit delta-sigma analog-to-digital converter (ADC) with integrated programmable gain amplifier (PGA), reference, temperature sensor and 4-input multiplexer. Measuring 2 mm x 1.5 mm, the ADS1118 is more than 65-percent smaller than any other 16-bit ADC available today. The ADS1118 provides direct, linearized measurements with uncalibrated error guaranteed below 0.5 degrees Celsius (C) from 0 degrees C to 65 degrees C, a 75-percent improvement over the competition. It is also the lowest-power 16-bit ADC with a built-in internal reference supporting data rates up to 860 samples per second.

Key features and benefits of the ADS1118

Integration reduces overall solution size:
Integrates a 16-bit ADC, PGA, temperature sensor, low-drift reference and 4-input multiplexer for data acquisition of multiple signals from a wide variety of sensors.

Small size saves board space:
Small QFN package option enables close proximity to sensors, lowering component count by simplifying cold junction compensation for thermocouples.

Low power extends battery life:
Supports 2.0-V to 5.5-V power supplies while consuming only 150 uA (typical) to extend the battery life of portable, battery-powered industrial devices for temperature measurement, gas monitoring, industrial process control, instrumentation and more.
Provides a complete data acquisition solution when paired with an MSP430™ microcontroller.

Tools and support

TI offers a variety of tools and support to speed development with the ADS1118, including an IBIS model, anti-aliasing filter tool for data converters and op amp to ADC circuit topography calculator. Engineers can also ask questions and help solve problems in the Precision Data Converter Forum in the TI E2E™ Community.

An evaluation module (ADS1118EVM), including software and source code, is available today for a suggested retail price of $49.

Availability, packaging and pricing

The ADS1118 is available now in a 5-mm x 3-mm MSOP package. Samples of the 2-mm x 1.5-mm QFN package are also available today with production quantities expected in December. Both package options are priced at $2.22 in 1,000-unit quantities

ti.com

SiC JFETs from SemiSouth target high-end audio

SemiSouth Laboratories, Inc., the leading manufacturer of silicon carbide (SiC) transistor technology for high-power, high-efficiency, harsh-environment power management and conversion applications, has launched a new family of low cost SiC JFETs with very good linearity targeted at high-end audio applications.

SJEP120R100A and SJEP120R063A offer a very good linearity and best-in-class distortion. Compatible with standard gate driver ICs, both versions feature a positive temperature coefficient for ease of paralleling; extremely fast switching with no'tail' current at up to a maximum operating temperature of 150degC and a low R_DS(on) max of 0.100Ω and 0.063Ω respectively. Devices are available in TO-247 packages; the 100mΩ part is also available in die form for integration into modules.

Comments Nelson Pass, founder of leading audio amplifier manufacturer Nelson Pass, Inc., "Over the last forty years I have greatly appreciated the qualities of lower power JFETs in audio circuits, and experimenting with the few examples of 'unobtainable' power JFETs has convinced me of their great potential. With the new SiC power JFETs from SemiSouth, this potential has been realized in reliable linear power amplifiers. In push-pull topologies, they exhibit a 50% to 70% improvement in distortion, and in single-ended circuits the improvement has been nearly ten-fold. Currently we profitably produce a small high-end audio amplifier using the SJEP120R100A devices and are engaged in developing other higher power amplifiers using this and the SJDP120R085 depletion mode devices."

Comments Dieter Liesabeths, SemiSouth's Vice President of Sales & Marketing, "These parts are especially suitable for high end audio amplifier designs which demand the best linearity performance and lower distortion. Compared to conventional SiC JFET for power applications, the prices for these audio parts has been reduced by about 15% in order to meet the demand of customers."

semisouth.com

Microchip Unveils Advanced Development Kit for High-Quality Digital Audio Applications

32-bit Microcontroller-based Dev Kit Provides Complete Solution for the Development of 24-bit Audio and Speech Applications With Record, Playback and Mixing Capabilities

Microchip Technology Inc., a leading provider of microcontroller, analog and Flash-IP solutions, today announced a 32-bit microcontroller (MCU)-based development kit for the creation of high-quality, 24-bit audio applications. The Audio Development Board for PIC32 MCUs features an 80 MIPS PIC32 MCU, a 24-bit Wolfson audio codec, a two-inch color LCD Display, a USB interface, and an onboard microphone. Supported by Microchip’s free software libraries, the kit provides a perfect solution for the development of speech and audio recording and playback products. Target applications include docks for portable audio players, home-entertainment systems and automotive sound systems.

The 80-MIPS PIC32MX795F512L MCU on the audio development board features 512 KB Flash and 128 KB RAM, providing plenty of processing power and memory to decode, analyze and play back audio and speech. Libraries are available for speech recording and playback, as well as MP3 music decoding applications. Additionally, an audio Sample Rate Conversion (SRC) library for33 kHz, 44.1 kHz and 48 kHz is also supported, which enables developers to reduce component costs for playback solutions. There are also libraries available for managing the USB interface and driving the on-board color LCD display, which features 16-bit color images. For those developers who are enrolled in the Apple Made For iPod (MFi) Licensing Program, the kit also interfaces to Microchip’s accessory development platform for iPod and iPhone.

“The Audio Development Board for PIC32 MCUs offers a complete platform that doesn’t break the budget for high-quality audio development,” said Sumit Mitra, vice president of Microchip’s High-Performance Microcontroller Division. “The board also includes an interface for use with our accessory development platform for iPod and iPhone, enabling expansion to support these popular devices.”

Packaging, Pricing & Availability

The Audio Development Board for PIC32 MCUs (part # DM320011) is available today, for $149.99 at microchipDIRECT (http://www.microchip.com/get/LJEC). For MFi licensees, the Digital Audio Development Kit for PIC32 MCUs (part # DM320411) adds the accessory development platform for iPod and iPhone. This kit will be available by September to MFi licensees via Apple's authorized distributor.

microchip.com

ELECTRONIC ASSEMBLY introduces OLEDs in Industrial Applications

Based on organic materials, OLED displays have become an integral part of mobiles and smartphones, thanks to their superb brightness. Now, Electronic Assembly, a manufacturer of displays, has introduced the technology to industrial applications.

With an extremely high contrast ratio of 2000:1, the nine OLED models from ELECTRONIC ASSEMBLY are real eye-catchers. The high contrast ratio is achieved by using a genuinely black background and active display technology. A new, patented system eliminates the relatively short service life of previous OLED displays. OLED displays from Electronic Assembly can be operated 100,000 hours and more at room temperature. Even when used at maximum operating temperature (80°C), they retain 50 percent or their original brightness after 14,000 hours.

The OLED displays also provide full contrast at temperatures down to -40°C. No contrast adjustment is required for this. Their response time of 10 microseconds gives the displays an extremely fast response time as well, whether they are used at high or low temperatures. In addition, information shown on the OLED displays is easy to read, no matter what the viewing angle.

All major character sets – English, European, Japanese, and Cyrillic – are integrated in the alphanumeric displays and do not need to be created by the controller. Connection to the outside world is similar to the established HD44780 standard via 4 and 8-bit interfaces. Power is provided by a 3 or 5-volt single supply, whereby the brightest brightness is achieved with the 5-volt supply. Consumption ranges between 15 and 50 milliamperes, depending on the size of the display.

Electronic Assembly offers nine different organic displays. Colors include yellow or white, and the display area encompasses 2 rows with up to 8 characters each or 4 rows with up to 20 characters each, depending on the model.

lcd-module.com

IAR Systems provides complete starter kit for high performance STM32 F-2 series of microcontrollers

IAR Systems today announced a complete starter kit for STMicroelectronics’ ARM Cortex-M3 based high performance STM32 F-2 series. The new leading-edge STM32F2xx series combines advanced 90nm process technology with the innovative adaptive real-time memory accelerator (ART accelerator) and the multi-layer bus matrix. IAR KickStart Kit for STM32F207 contains all the necessary hardware and software and allows embedded software applications to be designed, integrated and tested on hardware. It includes a feature-rich evaluation board, software tools, a debug probe, example projects and board support packages for several RTOSes. It is easy to use for evaluation and prototyping purposes thanks to a high level of integration between hardware, software and tools.

The evaluation board is fitted with an STM32F207ZG microcontroller, color LCD, connectors for USB host, USB OTG, Ethernet and CAN, headphone jack, and many other peripherals. Debug connectors for ETM trace, SWD and JTAG are also included.

The included IAR J-Link Lite debug probe provides JTAG and SWD debug interfaces. Added debug capabilities can be enabled by separate debug probes. IAR J-Trace enables full instruction trace, and IAR J-Link Ultra enables power debugging features in IAR Embedded Workbench. Both probes are sold separately.

The kit is prepared for use with IAR Embedded Workbench, the most widely used tool chain for ARM based microcontrollers recognized for its efficient code generation, comprehensive debugger, and user friendly IDE.

IAR KickStart Kit for STM32F207 is in stock and available in IAR Systems’ e-shop. It is priced at EUR 209/USD 289. Part number is KSK-STM32F207ZG-JL.

iar.com

IAR Systems launches starter kit for NXP's LPC11U00 USB microcontroller series

IAR Systems announced that an IAR KickStart Kit for the LPC11U00 series of microcontrollers is now available. It is a low cost starter kit for evaluation and for designing and prototyping software applications. The kit includes an LPC11U14 evaluation board fitted with an LPC11U14 microcontroller, a USB connector, an LCD, and various other peripherals, a J-Link Lite debug probe, software tools, example projects and board support packages for various RTOSes.

The NXP LPC11U00 series of microcontrollers provides low cost 32-bit replacement for 8- and 16-bit microcontrollers in USB device applications. It features an integrated USB 2.0 full-speed device controller together with an ARM Cortex-M0 processor.

IAR KickStart Kit for LPC11U14 is prepared for use with IAR Embedded Workbench, the most widely used tool chain for ARM based microcontrollers recognized for its efficient code generation, comprehensive debugger, and user friendly IDE.

IAR KickStart Kit for LPC11U14 is in stock and available in IAR Systems’ e-shop. It is priced at EUR 129/USD 179. Part number is KSK-LPC11U14-JL.

iar.com

IAR Systems releases complete starter kit for NXP's LPC1780 microcontroller series

IAR Systems announced a complete starter kit for NXP’s ARM Cortex-M3 based LPC1780 microcontroller family. IAR KickStart Kit for LPC1788 includes a feature-rich evaluation board, software development tools, an IAR J-Link Lite debug probe, and software. A high level of integration between hardware, software and tools in combination with pre-configured example projects and board support packages from various RTOS vendors makes it very easy to use the kit and get started with evaluation and development.

The evaluation board is fitted with an LPC1788 microcontroller, a 3,5’’ color TFT touch screen, connectors for USB host, USB OTG, Ethernet and CAN, audio in and out, and many other peripherals. Debug connectors for ETM trace, SWD and JTAG are also included.

Features

• Microcontroller
  • LPC1788FBD208 LQFP
• User interfaces
  • 2x user buttons
  • LCD 3.5’’ 320x200 24bit color TFT with backlight and touch screen
• Debug interfaces
  • JTAG/SWD connector - 20 pin 0.1’’
  • SWD connector - small 9 pin 0.05’’
  • ETMv3 connector - small 19 pin 0.05’’
• Communication interfaces
  • RS232/ICSP
  • USB host and OTG
  • CAN driver and connector
  • IrDA
  • 100 Mbit Ethernet 12C routed to connector
  • UXT connector
  • EXT connector
  • QEI connector
• Power functions
  • Multiple power supply options:
  • J-Link (pin 19)
  • Trace connector (pin 11&13)
  • External supply
  • Power supply LED
• Additional features
  • Audio in and out
  • SD/MMC card connector
  • Trimpot
  • Accelerometer

The included IAR J-Link Lite debug probe provides JTAG and SWD debug interfaces. Added debug capabilities can be enabled by separate debug probes. IAR J-Trace enables full instruction trace, and IAR J-Link Ultra enables power debugging features in IAR Embedded Workbench. Both probes are sold separately.

IAR KickStart Kit for LPC1788 is prepared for use with IAR Embedded Workbench, the most widely used tool chain for ARM based microcontrollers recognized for its efficient code generation, comprehensive debugger, and user friendly IDE.

IAR KickStart Kit for LPC1788 is in stock and available in IAR Systems’ e-shop. It is priced at EUR 279/USD 399. Part number is KSK-LPC1788-JL.

Atomic Force Microscope (AFM) and Scanning Tunneling Microscope (STM) and the different tools and techniques based on nanotechnology

In this article, the different tools and techniques that are used for producing and imaging a nanoscaled object is explained in detail. Atomic Force Microscope (AFM) and Scanning Tunneling Microscope (STM) is also explained in detail.

In Nanotechnology, the main scanning probes that have been used from the beginning are the Atomic Force Microscope (AFM) and Scanning Tunneling Microscope (STM). Both the concepts are explained in detail.

Atomic Force Microscope (AFM)

Atomic force microscopy (AFM) is also known as Scanning force microscopy (SFM). This device is used to visualizing, imaging, taking measures and for manipulating objects that are in nanometre scale. The resolution of such a device is said to be in the order of fractions of a nanometre. The earlier version of the AFM was called the Scanning Tunneling Microscope, developed in the early 1980’s. The AFM was developed in the year 1986 by Binnig, Quate and Gerber at the IBM Research – Zurich and earned them the Nobel Prize for Physics for the same year.

The device consists of a mechanical probe that is used to sense the material that is placed on the surface. A highly accurate scanning procedure then takes place, through which the corresponding electronic signals are generated using piezoelectric materials. If the variations are deeper in scale, they can also be measured using conducting cantilevers.

Working of Atomic Force Microscopy (AFM)

The block diagram of an AFM is shown below. From the figure it is understood that it has a sharp tip cantilever with a radius in nanometres, which is used to scan the surface of the material. The cantilever is made out of silicon or silicon nitride. The principle of Hook’s law is applied to the working of the cantilever. According to the law, a deflection will be produced by the cantilever as soon as the tip of it is brought closely to the surface of the material. This deflection is produced as a result of the forces that occur between the tip of the cantilever and the surface of the material.

Many parameters can be measured with the help of an AFM. Some of the common measurements that are taken are chemical bonding, Van der Waals force, mechanical contact force, capillary forces, Casimir forces, and so on. If additional probes are fitted to the device, many other parameters can also be measured. The detailed working of an Atomic Force Microscope (AFM) is shown in the figure below.

The deflection produced by the cantilever will be measured using a series of photodiodes which receives the laser signal from the top tip of the cantilever. There will be a problem of the tip causing damage if it is scanned at a constant height. To overcome this problem, a feedback mechanism is used to keep the same force between the tip and the sample throughout. Thus the distance between the tip and the sample will remain constant always.

In the case of the sample, its force is kept constant by mounting it on a peizo-electric tube. This tube has the capability to move the material in the x, y and z-directions. The movement in the x and y directions help in scanning the sample. The movement in the z direction keeps the force constant.

More problems regarding the distortion due to a tube scanner can be eliminated by configuring three peizo-electric crystals.

Different Modes

Depending on the needs, the AFM can be operated in a number of modes. Some of the basic modes are explained below.

• Static or Contact Mode

In such a mode, the cantilever is moved across the surface of the material, which produces a deflection on the cantilever tip. This deflection is directly measured to know the value. In such an operation, the deflection on the tip is used as the signal for feedback. As the deflection can cause noise and drift to the signal, low stiffness cantilevers are normally used to amplify it. When the cantilever comes close to the material, the attractive forces tend to glue them. Thus this method is always done in a contact where a repulsive force is present.

• Dynamic or Non-contact mode

In this mode, the cantilever is made to oscillate externally with a frequency very close to its real value. The characteristics of the material will be attained from the comparison of the external reference oscillation with the changes in oscillation due to the forces developed between the tip and the material in close contact.

There is no contact between the tip of the cantilever and the surface of the material. The cantilever is made to oscillate at a frequency greater than its resonant frequency in which the oscillation amplitude may be below 10 nanometres.

The resonant frequency of the cantilever decreases due to the presence of van der Waals forces or any other forces that have the ability to move over the material surface. This decrease in the frequency is added to the feedback loop system to obtain a constant oscillation amplitude or frequency. This can be done only by moving the average cantilever tip to material surface distance accordingly. The material surface can be easily sketched by calculating the tip to sample distance at each data point.

This mode is more useful than contact mode as there will not be any kind of sample degradation effects. Thus this mode is used for measuring soft materials. But if a rigid material is to be measured, both the modes have the same characteristics. If the AFM works in contact mode, it is able to scan the liquid layer of the material to capture the underlying surface. But, in non-contact mode, the AFM oscillates above the adsorbed fluid layer so that both the liquid and the surface can be scanned.

• Dynamic Contact or Tapping Mode

Dynamic contact mode was designed so as to overcome the problem that a non-contact dynamic mode faces at ambient conditions. The materials tend to form a liquid meniscus layer at ambient conditions. As a result of this condition, the non-contact dynamic mode finds it difficult to adjust the distance between the cantilever tip and the surface of the material. As they tend to glue together, the dynamic contact mode was developed to overcome this problem.

Just like a non-contact mode, the tip of the cantilever is fixed to a peizo-electric material. This material oscillates the cantilever to an up and down movement to values near the resonant frequency. But, the amplitude of oscillation will be more than 10 nanometres and near to 100 nanometres. As the tip of the lever gets closer to the material, the amplitude of oscillation reduces due to the different interaction of forces on the cantilever. The distance between the lever and the material is controlled by an electronic servo. While the lever scans the material the electronic servo moves the height to the correct position.

Measurement of the deflection caused by AFM cantilever

As shown in the figure above, the solid state diodes reflects the light back to the cantilever which is absorbed by a position sensitive detector (PSD). The PSD has 2 diodes which produces two outputs. These outputs are given to a differential amplifier. As there is a slight angular displacement in the lever, one photodiode carries more light than the other one. Thus, the output of the differential amplifier will be proportional to the deflection of the cantilever.

Other Tools and Techniques

• The very first devices that made us possible to see the nanoparticles were the scanning confocal microscope and the scanning acoustic microscope in the years 1961 and 1970. The latest techniques involve a method called position assembly in which the end of a scanning probe is used to make the nanoparticles visible.
• Some of the other tools that are needed in this field are for the application in nanolithography, a process that is used to reduce a big material to nanosize. Some of the methods that are used for this technique are optical lithography, X-ray lithography, dip pen nanolithography and so on.
• Different tools and techniques are also required for the fabrication of nanowires like electron beam lithography, nano-imprint lithography, atomic layer deposition, molecular vapour deposition, and so on. Techniques required for molecular self assembly also require tools.

Scanning Tunneling Microscope (STM)

Scanning Tunneling Microscope (STM) was developed in the year 1981 by Gerd Binnig and Heinrich Rohrer. An STM is used for imaging surfaces at the atomic level. The lateral resolution of an STM lies around 0.1 nanometre and depth resolution lies around 0.01 nanometre. This measure is more than enough to manipulate a good image. With this resolution, individual atoms within materials are routinely imaged and manipulated.

This method can be used in different modes like air, water, high vacuum, liquid and gas. It can also be used in very high and low temperatures. In an STM, when the tip of the device is brought near the material, a difference in voltage is applied between them. This difference causes the electrons to move through the empty space created between them. Such a method is called quantum tunneling.

As a result, a current is formed which depends on the position of the tip of the device, the applied voltage, and the local density of states (LDOS) of the sample. The image is displayed on a monitor according to the scanning process of the tip on the material.

The method is very precise unless and until the parameters are maintained according to standards. The tip of the device should be sharp, the surface should be clean and stable, the device should have better control on the vibrations produced.

Components used in STM

• Scanning tip
• Piezo-electric controlled height
• X-Y scanner
• Coarse sample-to-tip control
• Vibration isolation system
• Computer

Working of Scanning Tunneling Microscope

The tip of the device is moved closer to the sample in a controlled manner. At the same time a voltage difference is brought to the tip of the device. As soon as the tip reaches very close to the material, the voltage difference is turns off. The working of the device is clearly shown in the figure below. Take a look.

When the tip reaches close to the material, piezo-electric effect causes the accurate control of the tip. At such a situation the distance between the tip and the material is usually between (4-7) Å. At the same time the voltage difference in the tip causes the electrons to flow between the sample and the tip. This causes a current flow, whose reading is noted. As soon as the tunnelling effect starts to work, the distance between the tip and the material can be changed accordingly. An image is created according to the current readings. A movement of the tip in the X-Y direction causes a change in the height and density of the states. The height is in the Z-axis and can be measured with respect to a constant current. This method is called constant current method. In another method called the constant height method, the change in current with respect to position can be measured itself.

The image clarity depends on the radius of curvature of the scanning tip of the device. The image can also be distorted if the tip of the device has two ends rather than one. If such a condition occurs, it will lead to tunnelling effect from both the tips. Such a condition is called double-tip imaging. The material used for making the tip is mostly tungsten or gold. The tip is designed using electro-chemical etching.

The body of the STM has to be highly rigid in order to avoid the sudden isolations that may occur during the scanning process. If such a problem happens the current to height ratio changes thus deforming the image.

The computer is responsible for keeping the position of the tip in the correct position w.r.t the sample, sample scanning and also data acquisition.

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nanotechnology implications

In this article, the different implications in nanotechnology is explained in detail. The benefits f nanotechnology in different fields along with the health implications is explained in detail.

The fields in which the implication of nanotechnology extends are numerous. Some of the most common fields are computing, engineering, biology, chemical, communications, material science different systems and many more.

Through nanotechnology, there are a lot of benefits and improvements in a various field of technology. Some of the processes and fields that will be improved with the help of nanotechnology are listed below.

• It helps in improving the manufacturing methods of various devices.
• Different physical processing systems like water purification process, energy processing, and so on will improve.
• The change in the size and shape of many physical devices helps in attaining smart devices with better performances.
• The complete method of food production can be made better with more nutrition. Through this technology, the productivity can be increased to greater heights without waste of time and labour.
• The technology also helps in the field of medicine, where better drugs can be made in great amounts at a very small time.
• Large scale infrastructure auto-fabrication can also be introduced.
• Since the size of different objects change with this technology, it will pave way for better automation as there exists tasks which are not possible to be done by humans or machines due to physical restrictions. Thus, the automation can be easily done by smaller robots which reduce the labour costs, and maintenance costs as well.
• The materials will be environmental friendly and can provide clean water for all through the simplest methods.

Along with the benefits there also arise some hazards which have to be dealt with safety issues.

Some of the basic risks include that related to health and safety. The environmental hazards that can happen due to the waste of materials that will have to be thrown out to pave way for nanotechnology materials is one big problem. The biological hazards that can happen due to the strong drugs that can be made by this technology is also a problem. Problems may also arise due to privacy invasion through nanosensor surveillance.

Health implications of Nanotechnology

Studies are going on knowing the extent of both benefits and risks that nanotechnology imposes on the human health. Mainly two types of studies are going on for this purpose. They are

• The advantage of nanotechnology which leads to the cure of all diseases that affect human health.
• The disadvantages that cause hazards to the human body due to the exposure to nanotechnology.

When the nanoparticles are introduced to our body, they will be readily accepted by our body than large sized particles.

There are still unclear ideas on the way the human body will respond to these particles. Due to their small size they could easily react with the surrounding tissues and destroy the foreign matter, clearly eliminating the defence mechanism of the body. Another major problem is regarding their reaction with the biological process inside the human body. When they hit the tissue walls they may absorb some of the macro molecules that come in their path. This will clearly disturb the working of enzymes and proteins inside the body.

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carbon-nanotube-composites used for airplanes-to-be-built

As explained earlier, the nanomaterials are lighter, stronger and long lasting than other materials. This advantage has been exercised in replacing the aluminium body of airplanes with composite materials including nanomaterials.

As such a composite material has less weight; the whole body weight of the airplane will almost reduce to half the original weight. This will help in reducing the fuel consumption of the airplane. Another advantage is regarding the change in shape when an accident occurs. When a plane made of aluminium comes in contact with a barrier, a change in shape occurs, which causes serious internal damage. But if a plane made of composite material comes in contact with a barrier, the material will first deform and will suddenly spring back to its original shape. Researchers are trying to conduct several tests to see how much the material can withstand. One test includes the amount of heat transfer that occurs through the material body. To do this, large heat producing systems were installed in many sections of the airplane. High amount of heat was applied and the changes that occur were captured by a heat sensitive camera. The expense for such an experiment is very high as it requires bulky and complex equipments.

If the composite includes carbon nanotubes, the heat response of the material changes. A small electric current will cause a high increase in temperature of the nanotubes. Any internal damages will still change the heat flow, which can be picked up by the thermal camera.

If the experiment becomes a success, we can see airplanes that are made out of a whole new material with better performance and better safety.

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basics of Nanoelectronics

This article explains the basics of Nanoelectronics and its concept. The different approaches are also explained in detail.

Nanoelectronics are based on the application of nanotechnology in the field of electronics and electronic components. Although the term Nanoelectronics may generally mean all the electronic components, special attention is given in the case of transistors. These transistors have a size lesser than 100 nanometres. Visibly, they are very small that separate studies have to be made for knowing the quantum mechanical properties and inter-atomic design. As a result, though the transistors appear in the nanometre range, they are designed through nanotechnology. Their design is also very much different from the traditional transistors and usually falls in the category of one dimensional nanotubes/nanowires, hybrid molecular electronics, or advanced molecular electronics.

This technology is said to be the next future, but its practicality is near to impossible even now that they may be difficult to emerge soon.

Basic Concept of Nanoelectronics

Although a nanoelectronic device can be made fully functional, the work load it can do is restricted to its size. The basic principle is that the power of a machine will increase according to the increase in volume, but the amount of friction that the machine’s bearings hold will depend on the surface area of the machine.

For the small size of the nanoelectronic device cannot be used for the moving of heavy load like a mechanical device. If such a task is tried, it will fail as the available power will be easily overcome by the frictional forces. So, it is sure that these devices have limitations in real world applications.

Different Approaches to Nanoelectronics

• Nanofabrication

This method is used to design arrays or layers of nanoelectronic device to work for a single operation. Nanoelectromechanical systems are also a part of nanofabrication.

• Nanomaterials electronics

In Nanoelectronics, the transistors are packed as arrays on to a single chip. Thus they remain in a uniform manner and symmetrical in nature. Thus they are known to have a more speedy movement of electrons in the material. The dielectric constant of the device also increases and the electron or hole characteristics also become symmetrical in nature.

Some of the devices that have been developed with the help of Nanoelectronics and its future applications are listed below.

• Nanoradio
• Nanocomputers

The conventional computers with a big processor will be replaced with Nanocomputers with nanoprocessors that will have higher performance and speed than the conventional computers. Researchers are performing various experiments on by using nanolithographic methods to design better nanoprocessors. Experiments are also taking place by replacing the CMOS components in conventional processors with nanowires. The FET’s in the computers are replaced by carbon nanotubes.

• Energy production

The devices using Nanoelectronics technology also includes solar cells that are highly efficient and cheaper than the conventional ones. If such efficient solar energy can be created it would be a revolution to the global energy needs.

Using the technology, researchers are developing a generator for energy production in vivo called bio-nano generators. Basically, the generator is an electrochemical device which is designed in nanoscale size. It works like a fuel cell which generates the power by absorbing the blood glucose in a living body. The glucose will be separated from the body with the help of an enzyme. This enzyme separates the glucose from the electrons and makes them useful for generating power.

The power generated through such a device will be only a few watts as the body itself needs some glucose for its normal functioning. This small power can be used to power up devices placed inside the body like pacemakers or sugar-fed nanorobots.

basic nanocircuitry explanation

In this article the basic nanocircuitry is explained in detail. The different parameters like transistors, interconnections and architecture are also explained in detail. The implementing methods and production methods are also explained in detail.

As the term implies, nanocircuits are basic electrical circuits that are designed and operated in the nanometre scale. Even though, the nanocircuit of a processor that is used nowadays will be billion times smaller, the performance will be moreover the same with perhaps greater efficiency. Thus hundreds of nanocircuits can be added together to form a high performance and highly efficient processor. In the case of nanocircuits, it mainly constitutes three basic components. They are

1. Transistors

Transistors are used in most electronic circuits as they help in amplifying the weak signals and converting them to strong ones, turn on or off the current through the circuit, and also help in directing the flow of electricity. The transistors used in electronic circuit are made out of silicon as the material an easily switch between the conducting and non-conducting states. When it comes to nanocircuits, the silicon will be replaced by inorganic structures or organic molecules in the nanoscale.

2. Interconnections

Interconnections refer to the connections between the transistors and other wires in a single device or chip. These interconnections can be done only with the help of logical and mathematical operations. The transistors inside a nanocircuit will be connected together with the help of nanowires which have a thickness of only 1 nanometre. The nanowires are made from carbon nanotubes. But recently, researchers were able to develop nanowires with the integration of transistors in it. Thus the difficulty in stringing the transistors on to the nanowires has been overcome.

3. Architectures

The architecture of the nanocircuit is basically the design of the device and has been already discussed in the above topics. As the circuit is very small in nature, they are liable to have more defects. With the help of a good structure combining with redundant logic gates, the whole design can be reconfigured at greater levels of the chip. Thus problems that are liable to happen in the future can be easily repaired.

Implementing Nanocircuits

Many methods are being tried out to implement nanocircuits in the best way possible. Some of the common methods that have been tried out are

• Quantum dot cellular automata
• Single-electron transistors and
• Nanoscale crossbar latches

But, researchers are now more interested in incorporating nanocircuitry with semiconductor devices like MOSFET’s. Since MOSFET’s are used in most of the analog and digital circuit designs, their scaling down will be of great importance in the coming future.

Out of all the FET’s the nanoscale reduction was most successful with the circular cross section vertical channel field effect transistor.

A company called nanosys was able to develop a lateral channel on an FET using nanowires to design the substrates. These nanowires were made using different aligning methods and solution based deposition. Though the total size of such a component was not reduced to that of a single nanowire FET the reliability of the material was much higher. As usual fabrication processes are enough for such a design large volume printing can be easily done at reasonable costs. Such an FET can be made by low temperature deposition and hence can be used as the carrier substrate for transistors. This feature helps in making different electronic devices like electronic paper, bendable flat panel displays and also wide area solar cells.

Production Methods

The basics of nanocircuits and its production mainly depend on the Moore’s Law.

The law is used to relate the number of transistors that can be added to a silicon IC with its computing speed. If more transistors are added, the faster the computing speed.

This is the main reason that nanocircuits are being developed so that more billions of transistors can be integrated onto a single chip to form a super computer. The only problem that will arise with such a sleek design is the defects in the transistor alignment. Nanocircuits will have more problems than larger chips as they are more sensitive to cosmic rays, electromagnetic interference and also temperature variations.

As these transistors will be closely packed, the number of unwanted signals may increase and interference problems may occur. Even the heat produced is difficult to dissipate. Another problem will be the tunneling over the insulation barriers and the fabrication difficulties which will decrease the efficiency of the device.

Due to all these reasons, there will be a delay in the official release of nanocircuits in the market and will mostly be ready by 2016. But, for the production of such devices, the investments should be as high as $250 billion. The principle of Moore’s law is also likely to diminish as there will be a future when the speed of computers will reach a maximum level.

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Drug Resistant Bacteria killed using new nanomaterial specially developed

Nanotechnology has once again proved its worth in the medical field. Researchers had recently developed a solution that can be rubbed on the skin to remove all bacteria’s that cannot be killed by the existing antibiotics and drugs. More advanced studies have led to the discovery of a microbial agent that can be directly injected into the body to kill the strong bacteria’s.

The basic semiconductor manufacturing principle was used to manufacture such an agent. The research team included people from the Institute of Bioengineering and Nanotechnology and IBM.

The product developed has special physical features like magnets. They get attracted to the bacteria’s like Methicillin-resistant Staphylococcus Aureus (MRSA) and are not attracted to the healthy cells inside the body. Thus the bad microbes can be easily sorted out and destroyed.

Bacteria’s like MSRA and its types are very common in crowded places like schools, offices, hospitals and so on. They are very difficult to be traced out and cannot be permanently destroyed with the help of the usual antibiotics and lotions. In order to destroy them high intake of antibiotics will be needed. But this will bring unwanted reactions onto the patient. Reports have proved that almost a million people die every year due to MSRA bacteria infection.

The greatest feature of the nanomaterial is that it can break into the cell membrane and directly destroy the bacteria.

According to Doctor James Hedrick, an Advanced Organic Materials Scientist at IBM in Almaden, the number of bacteria in the palm of a human hand is more than the total human population. Through this invention, the “search of a lifetime” for the accurate drug delivery mechanism has come to its end.

If the research turns out to be successful (that is after testing for body reactions to the agent), there will be a future when this material can be mixed with lotions, soaps and deodorants and also in injections. They could also prove to be worthy in healing internal wounds and lung infections.

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DC motor speed control low voltage circuit

Description.

Here is the circuit diagram of a low voltage /low power DC motor speed controller based on the IC TDA 7274 from ST Microelectronics. The IC TDA 7274 is a monolithic integrated DC motor speed controller intended for low voltage/ low power applications. Built in internal voltage reference voltage, wide input voltage range (1.8 t0 6V), high linearity, 700mA output current, excellent temperature stability etc make this IC well suitable for almost all low power DC motor speed control applications.
The motor to be controlled is connected between pin3 (Vs) and pin4 (output) of the IC. Resistor network comprising of R1, R2, and R3 is the section that deals with the speed control. Control pin (pin8) of the IC is connected to the junction of R2 and R3 and the speed of the motor varies linearly according to the position of POT R3. Capacitor C1 rectifies the fluctuations in motor speed and capacitor C2 cancels the motor spikes.

• The circuit can be assembled on a Perf board.
• Power supply Vs can be anything between 1.8V to 6V and it must be selected according to the rating s of the motor.
• Maximum output current capacity of this circuit is 700mA.
• TDA7274 must be mounted on a holder.
• POT R3 can be used to vary the motor speed.

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Motor speed controller (PWM)

Description.

This circuit is designed as per a request made by Mr Vinoth from India. His requirement was a 12V/5A DC fan motor controller. I think this circuit is sufficient for this purpose. Quad 2 input Schmitt trigger IC CD4093 is the heart of this circuit. Out of the four Schmitt triggers inside the 4093, U1a is wired as an oscillator with adjustable duty cycle. The U1b, U1c, U1d buffers the output of the oscillator to drive the switching MOSFET Q1.The MOSFET drives the DC motor according to the switching pulse obtained from the oscillator. When R1 is varied the duty cycle varies and so do the speed of the motor. Diode D3 acts as a freewheeling diode.

• Assemble the circuit on a good quality PCB.
• IC U1 should be mounted on a holder.
• U1a, U1b, U1c, U1d are part of the same IC CD4093; so power supply is shown connected only once.
• The12V power supply for this circuit must be able to handle at least 5A.
• A heat sink is recommended for Q1.

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MC3479 from Motorola based a stepper motor driver

The circuit diagram given here is of a stepper motor driver using MC3479 from Motorola. The MC3479 is specifically designed for driving a 2 phase stepper motor in bipolar mode and is available in standard DIP and surface mount packages.The IC is compatible to TTL and CMOS inputs and has selectable HIGH/LOW output impedance. The output can deliver up to 350mA each of two coils of a 2 phase stepper motor. The state change of the output occurs at the low to high transition of the input clock pulse. The new output will depend on old output and the state of the digital inputs. The output L1 to L4 are high currents outputs, which when connected to a two phase stepper motor forms two full bridge formations.

Resistors R1 & Rb, Zener diode D1 and IC2 MC14049UB are the additional components used in the circuit. R1 is a pull up resistor and Rb is used to set the maximum output sink current. Zener diode D1 provides back emf protection.

Notes.

• Assemble the circuit on a good quality PCB.
• The supply voltage (+V) can be 7 to 16V DC depending on the stepper motor used.
• Maximum possible current per coil is 350mA.
• Value of the resistor Rb can be obtained from the equation Rb = (Vm – 0.7V)/Ibs.
• Where Ibs = Iod X 0.86.( Vm is the supply voltage itself and Iod is the current per coil).
• Pin10 (CW/CCW) is used to select clock wise or counter clock wise rotation.
• Pin 7 (clock) is the clock input pin.
• Pin 9 (full/half step) is used to select between full and half steps.
• Pin8 (OIC) is used for output impedance control.

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simple circuit for controlling the speed of DC operated PCB drills

Description.
Here is a simple circuit for controlling the speed of DC operated PCB drills. The heart of this circuit is the ICLM3578 which is a very efficient integrated switching regulator that can be used for applications like this. The LM3578 has separate inverting and non inverting feedback inputs (pin1 and pin2), 1V internal reference voltage source and a built in oscillator circuit. The IC can be configured to obtain up to 90% duty cycle. In the circuit, capacitor C2 is the timing capacitor which determines the frequency of the internal oscillator. The duty cycle depends on the sum of resistors R1 and R2 and it can be varied by adjusting the POT R2. The output PWM signal will be available at pin 5 of the IC. The Q1 drives the motor M according to the PWM signal available at pin5 and thus by varying the duty cycle of the PWM wave by varying POT R2, the speed of the motor can be adjusted. The diode D1 is a freewheeling diode which protects the MOSFET Q1 from transients produced by the motor. Capacitor C3 is just a filter capacitor.

• The circuit can be assembled on a Vero board.
• The supply voltage (V+) can be anything between 6 to 30V DC.
• The supply voltage (V+) must be selected according to the voltage rating of the drill motor.
• The maximum drain current IRF540 can handle is 22A @ room temperature.
• The duty cycle can be varied from 0 to 90% by adjusting the POT R2.

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switch ON automatic cooler fan for audio amplifiers

Description.

The schematic of an automatic cooler fan for audio amplifiers is given here. The circuit automatically switch ON the cooler fan whenever the temperature of the heat sink exceeds a preset level. This circuit will save a lot of energy because the cooler fan will be OFF when the amplifier is running on low volume. At low volume less heat will be dissipated and it will not trigger the cooler fan ON.

The temperature is sensed using an NTC (negative temperature coefficient) thermistor R2. Junction of thermistor r2 and resistor R1 is connected to the inverting input (pin3) of IC1 which is wired as a comparator. The non-inverting input (pin2) is given with a reference voltage using the preset R3. As temperature increases the resistance of NTC thermistor will drop and so do the voltage across it. When the voltage at the inverting input becomes less than that of the reference voltage (set for a particular threshold temperature) the output of the comparator goes high and switches the transistor Q1 ON. This will activate the relay and the cooler fan will be switched ON. When the temperature decreases the reverse happens. LED D2 will glow when the fan is ON. Diode D1 is a freewheeling diode.

• The circuit can be assembled on a Vero board.
• Use 12V DC for powering the circuit.
• The circuit can be calibrated by adjusting the preset R3.
• K1 can be a 12V, 200 ohm, SPST relay.
• LM311 must be mounted on a holder.

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using easily available components a simple H bridge motor driver circuit

Description.

The circuit give here is of a simple H bridge motor driver circuit using easily available components. H Bridge is a very effective method for driving motors and it finds a lot of applications in many electronic projects especially in robotics.

The circuit shown here is a typical four transistor H Bridge. The diodes D1 to D4 provide a safer path for the back emf from the motor to dissipate and thus it protects the corresponding bipolar transistors from damage. Resistors R1 to R4 limit the base current of the corresponding transistors. Working of this circuit is very easy to understand. When terminal D is grounded and A is pulled to +Vcc, transistors Q1 and Q4 will be on and current passes through the motor from left to right. When terminal B is grounded and C is pulled to +Vcc, transistors Q3 and Q2 will be on and current passes through the motor from right to right making the motor to rotate in the opposite direction.

NOTES:

• The circuit can be assembled on a Vero board.
• The maximum possible collector current of 2N2222 is 800mA and that for 2N2907 is 600mA.
• A DC brush type motor is used here.
• Do not use a motor that draws more than 600mA of current.
• +Vcc can be anything between 3 to 15V DC depending on the voltage rating of the motor used.
• Do not connect terminal D to ground and C to +Vcc same time, it will result in short circuit.
• Do not connect terminal B to ground and C to +Vcc same time, it will also result in short.
• Resistors R1 to R4 limit the base current of the corresponding transistors. By altering their value, you can alter the motor current.

S:circuitstoday.com