Add-On Stereo channel selector

The add-on circuit presented here is useful for stereo systems. This circuit has provision for connecting stereo outputs from four different sources/channels as inputs and only one of them is selected/ connected to the output at any one time. When power supply is turned ‘on’, channel A (A2 and A1) is selected. If no audio is present in channel A, the circuit waits for some time and then selects the next channel (channel B), This search operation continues until it detects audio signal in one of the channels. The inter-channel wait or delay time can be adjusted with the help of preset VR1. If still longer time is needed, one may replace capacitor C1 with a capacitor of higher value. Suppose channel A is connected to a tape recorder and channel B is connected to a radio receiver. If initially channel A is selected, the audio from the tape recorder will be present at the output. After the tape is played completely, or if there is sufficient pause between consecutive recordings, the circuit automatically switches over to the output from the radio receiver. To manually skip over from one (selected) active channel, simply push the skip switch (S1) momentarily once or more, until the desired channel inputs gets selected. The selected channel (A, B, C, or D) is indicated by the glowing of corresponding LED (LED11, LED12, LED13, or LED14 respectively). IC CD4066 contains four analogue switches. These switches are connected to four separate channels. For stereo operation, two similar CD4066 ICs are used as shown in the circuit. These analogue switches are controlled by IC CD4017 outputs. CD4017 is a 10-bit ring counter IC. Since only one of its outputs is high at any instant, only one switch will be closed at a time. IC CD4017 is configured as a 4-bit ring counter by connecting the fifth output Q4 (pin 10) to the reset pin. Capacitor C5 in conjunction with resistor R6 forms a power-on-reset circuit for IC2, so that on initial switching ‘on’ of the power supply, output Q0 (pin 3) is always ‘high’. The clock signal to CD4017 is provided by IC1 (NE555) which acts as an astable multivibrator when transistor T1 is in cut-off state. IC5 (KA2281) is used here for not only indicating the audio levels of the selected stereo channel, but also for forward biasing transistor T1. As soon as a specific threshold audio level is detected in a selected channel, pin 7 and/ or pin 10 of IC5 goes ‘low’. This low level is coupled to the base of transistor T1, through diode-resistor combination of D2-R1/D3-R22. As a result, transistor T1 conducts and causes output of IC1 to remain ‘low’ (disabled) as long as the selected channel output exceeds the preset audio threshold level. Presets VR2 and VR3 have been included for adjustment of individual audio threshold levels of left stereo channels, as desired. Once the multivibrator action of IC1 is disabled, output of IC2 does not change further. Hence, searching through the channels continues until it receives an audio signal exceeding the preset threshold value. The skip switch S1 is used to skip a channel even if audio is present in the selected channel. The number of channels can be easily extended up to ten, by using additional 4066 ICs.

Digital Set-Top Boxes and Integrated Digital Television Systems

Digital set-top boxes (DSTBs) receive and decode television broadcasts from satellite, cable, and/or terrestrial sources. Integrated digital televisions (DTVs) have built-in digital tuners, demodulators, and source decoders, so they do not require digital set-top boxes that receive digital broadcasts. Traditional DSTBs are designed to receive standard definition (SD) Moving Pictures Experts Group-2 (MPEG-2) video format broadcasts. However, many of today’s DSTBs are high-definition (HD)-ready. In fact, selected cable television service providers, networks, and local terrestrial TV stations are concurrently transmitting both SD and HD content. Over time, MPEG-4 will displace the MPEG-2 format for both SD and HD. When MPEG-4 becomes the standard compression standard, systems implementing reprogrammable logic devices (such as FPGAs) will be able to seamlessly upgrade without having to scrap inventory items or make new hardware. Using FPGAs, manufacturers can design a STB that can decode MPEG-2 video format, and then later upgrade that same STB for MPEG-4 by simply reprogramming the FPGA in-system. High-end DSTBs usually offer personal video recorder (PVR) and/or an HD DVD recorder for Blu-ray functions. Microcontrollers in DSTBs or integrated DTVs can perform a number of functions for these systems, including control panel management and on-screen display (OSD). Many current DSTBs can be classified either as free to air (FTA) or pay TV versions. A pay TV example would be DSTBs designed for DirecTV or Dish Network (in the USA), which require conditional access to decode the audio and video. DSTB manufacturers typically design the PCBs for both low-end and high-end DSTB systems and require a flexible solution for implementing their various designs.

LED's and OPTICS

LED stands for Light Emitting Diode.  LED's convert an electrical current directly into light.  The light emitted by an LED is directly proportional to current through the LED.  This means LED's are ideal for transmission of information.   However, LED's need direct line of sight and they usually have a short range of light emission.  Because LED's are current dependent they need to be protected from excessive current with a resistor.  For most robotic applications with power sources of around 9 volts I find that a 1K resistor will always to the trick.  You'll notice one lead is longer than the other, in most cases a longer lead indicates that it is the positive lead.  It might be easy to dismiss the LED and assume all it does is light up, but LED's are very interesting electronics components and have some surprising functions.  For instance if you take a Jumbo LED (of any color) and connect your Multimeter up to it for voltage reading and point the LED towards a very bright light source you'll get a voltage reading.  In direct sunlight you can get a reading of 1.5 volts from a normal LED!  Some people even think it is possible to make a color sensor using a LED like this, however after much experimenting with this It is found that LED's to not be suitable for use as a sensor.

Capacitors

Capacitors have 3 primary functions:

1. To store a charge, much like a battery. These capacitors are normally
electrolytic and are used in situations like power supplies where a
fluctuating DC voltage needs to be smoothed, or, have the ripple taken out.

2. A capacitor is used to block DC while allowing AC to pass through such
as in an audio amplifier where we are passing the audio signal through from
one stage to the next.

3. To counteract inductive reactance in order to create a "tuned circuit".

4. A cap can also be used as a spike filtering, which is slightly different than smoothing an AC signal. The term for this purpose is "bypass cap" in case anyone out there was wondering about that one.

When power gets to them they hold a charge right away, but will eventually discharge if left alone or you can discharge a capacitor by hitting both of it's leads together or connect a resistor between both leads.  Capacitors have different levels, which are specified in farads.  Below are common schematics symbols for capacitors and common farad ratings.

1-Farad = 1F 1-Microfarad = 1mF or uF = .000001F 1-Picofarad = 1pF - .000000000001F

C1 shows a normal fixed capacitor, these you can connect in like resistors.  C2 shows one that is polarized, this means you must connect it's positive lead the most positive connection point in it's placement. With polarized capacitors you'll mind that they are marked with either a plus to show the positive side or with a negative to show the negative side.  C3 shows a variable capacitor, I have yet to see one of these in a circuit.

Capacitors are not color-coded but they do have a numbering system that tells you what their value is.  This can be tricky to find the value of an odd capacitor but most of the time you'll see number like this: 151K  The first and second digits are the capacitors value.  For the third number find it's multiplier value on the chart to the left and simple multiply.  So 151K is a 150pF capacitor.  You might also see a notation like this, EG 104 or 104K both of which are .1uf caps.  Caps, of course here is short for capacitor.

The letter tells you the tolerance of the cap, you can look up the tolerance on this chart.  A note I want to add to this capacitor section is that sometimes you may see the letter R on a cap, which would signify a decimal point.  So if you see 2R2 that would equal 2.2 (pF or uF).  My best advice is to keep your capacitors well organized and with their packaging if you are not confident you can distinguish one capacitor from another.

An important thing to take notice of is that capacitors DO NOT add in series like resistors, just the opposite, two 1mfd capacitors in series equal 0.5 mfd.

At ‘four sales a second’, Samsung’s Galaxy S4 passes 10 million mark in first month

“Launched globally on April 27, the phone is estimated to be selling at a rate of four units per second,” Samsung said in a statement announcing the news.

The Android-powered Galaxy S4, with its 5-inch 441-PPI display, 13-megapixel camera and slew of snazzy features, is evidently proving a big hit with consumers in the 110 countries where its currently sold. Ten million sales in less than a month makes sales of the previous iterations of the handset appear positively sluggish, though they were, of course, considered impressive at the time.

The Galaxy S3 crossed the 10-million mark 50 days after its launch in May last year, while the S2 took five months to reach the same milestone. As for the Galaxy S, the first handset in the range, that took all of seven months to sell 10 million units after launching in 2010.

“On behalf of Samsung, I would like to thank the millions of customers around the world who have chosen the Samsung Galaxy S4,” Samsung co-CEO JK Shin said in the statement. “At Samsung we’ll continue to pursue innovation inspired by and for people.”

The Galaxy’s S4’s impressive sales figures also indicate a narrowing of the gap previously comfortably enjoyed by Apple with its iPhone – for the first three months of this year, Apple sold an average of 12.5 million handsets per month. Could we see the S4 outselling the iPhone before the end of 2013, or will sales  tail off once the initial enthusiasm for the handset fades?

Late last year it was reported that Samsung is aiming to sell more than 500 million smartphones and feature phones in 2013, improving on sales in 2012 by around 20 percent. Based on Wednesday’s news, phones in the company’s Galaxy S range are likely to make up a sizable proportion of those sales.

In other S4 news, Samsung says in the summer it’ll be launching the S4 in a variety of new colors – Blue Arctic and Red Aurora, followed by Purple Mirage and Brown Autumn – to go with the currently available White Mist and Black Forest offerings.

ACCURATE ELECTRONIC STOP-WATCH

Here is a simple circuit which can be used as an accurate stop-watch to count up to 100 seconds with a resolution of 0.01 second or up to 1000 seconds with a resolution of 0.1 second. This stop-watch can be used for sports and similar other activities. A 1MHz crystal generates stable frequency which is divided by two stages of 74390 ICs (dual decade counter) and another stage employing 7490 (decade counter) IC to obtain a final frequency of 100 Hz or 10 Hz. Due to the use of crystal, the final frequency is very accurate. The output of IC4 (7490) is counted and displayed using IC5 74C926 (4-digit counter with multiplexed 7-segment LED driver). Due to multiplexed display the power consumption is very low. Switch S2 (2-pole, 2-way) is used to select appropriate input frequency and corresponding decimal point position to display up to either 99.99 seconds or 999.9 seconds maximum count. For proper operation, first press switch S3 (reset) and then operate switch S2, according to the resolution/range desired (0.1 sec. or 0.01 sec.)/(100 seconds or 1000 seconds). Now to start counting, press switch S1. To stop counting, press switch S1 again. The counting will stop and display will show the correct time elapsed since the start of counting.

Resistor colour codes

Logic Gates

Small in Size, Big On Power: New Microbatteries the Most Powerful Yet

Though they be but little, they are fierce. The most powerful batteries on the planet are only a few millimeters in size, yet they pack such a punch that a driver could use a cellphone powered by these batteries to jump-start a dead car battery -- and then recharge the phone in the blink of an eye. Developed by researchers at the University of Illinois at Urbana-Champaign, the new microbatteries out-power even the best supercapacitors and could drive new applications in radio communications and compact electronics.

Led by William P. King, the Bliss Professor of mechanical science and engineering, the researchers published their results in the April 16 issue of Nature Communications.

"This is a whole new way to think about batteries," King said. "A battery can deliver far more power than anybody ever thought. In recent decades, electronics have gotten small. The thinking parts of computers have gotten small. And the battery has lagged far behind. This is a microtechnology that could change all of that. Now the power source is as high-performance as the rest of it."

With currently available power sources, users have had to choose between power and energy. For applications that need a lot of power, like broadcasting a radio signal over a long distance, capacitors can release energy very quickly but can only store a small amount. For applications that need a lot of energy, like playing a radio for a long time, fuel cells and batteries can hold a lot of energy but release it or recharge slowly.

"There's a sacrifice," said James Pikul, a graduate student and first author of the paper. "If you want high energy you can't get high power; if you want high power it's very difficult to get high energy. But for very interesting applications, especially modern applications, you really need both. That's what our batteries are starting to do. We're really pushing into an area in the energy storage design space that is not currently available with technologies today."

The new microbatteries offer both power and energy, and by tweaking the structure a bit, the researchers can tune them over a wide range on the power-versus-energy scale.

The batteries owe their high performance to their internal three-dimensional microstructure. Batteries have two key components: the anode (minus side) and cathode (plus side). Building on a novel fast-charging cathode design by materials science and engineering professor Paul Braun's group, King and Pikul developed a matching anode and then developed a new way to integrate the two components at the microscale to make a complete battery with superior performance.

With so much power, the batteries could enable sensors or radio signals that broadcast 30 times farther, or devices 30 times smaller. The batteries are rechargeable and can charge 1,000 times faster than competing technologies -- imagine juicing up a credit-card-thin phone in less than a second. In addition to consumer electronics, medical devices, lasers, sensors and other applications could see leaps forward in technology with such power sources available.

"Any kind of electronic device is limited by the size of the battery -- until now," King said. "Consider personal medical devices and implants, where the battery is an enormous brick, and it's connected to itty-bitty electronics and tiny wires. Now the battery is also tiny."

Now, the researchers are working on integrating their batteries with other electronics components, as well as manufacturability at low cost.

"Now we can think outside of the box," Pikul said. "It's a new enabling technology. It's not a progressive improvement over previous technologies; it breaks the normal paradigms of energy sources. It's allowing us to do different, new things."

The National Science Foundation and the Air Force Office of Scientific Research supported this work. King also is affiliated with the Beckman Institute for Advanced Science and Technology; the Frederick Seitz Materials Research Laboratory; the Micro and Nanotechnology Laboratory; and the department of electrical and computer engineering at the U. of I.

VISUAL AC MAINS VOLTAGE INDICATOR

You should not be surprised if someone tells you that the mains voltage fluctuation could be anywhere from 160 volts to 270 volts. Although majority of our electrical and electronics appliances have some kind of voltage stabilisation internally built-in, more than 90 per cent of the faults in these appliances occur due to these power fluctuations. This simple test gadget gives visual indication of AC mains voltage from 160 volts to 270 volts in steps of 10 volts. There are twelve LEDs numbered LED1 to LED12 to indicate the voltage level. For input AC mains voltage of less than 160 volts, all the LEDs remain off. LED1 glows when the voltage reaches 160 volts, LED2 glows when the voltage reaches 170 volts and so on. The number of LEDs that glow keeps increasing with every additional 10 volts. When the input voltage reaches 270 volts, all the LEDs glow. The circuit basically comprises three LM339 comparators (IC1, IC2 and IC3) and a 12V regulator (IC4). It is powered by regulated 12V DC. For power supply, mains 230V AC is stepped down to 15V AC by stepdown transformer X1, rectified by a bridge rectifier comprising diodes D1 through D4, filtered by capacitor C4 and regulated by IC4. The input voltage of the regulator is also fed to the inverting inputs of gates N1 through N12 for controlling the level of the AC. The LED-based display circuit is built around quad op-amp comparators IC1 through IC3. The inverting input of all the comparators is fed with the unregulated DC voltage, which is proportional to mains input, whereas the non-inverting inputs are derived from regulated output of IC4 through a series network of precision resistors to serve as reference DC voltages. Resistors R13 to R25 are chosen such that the reference voltage at points 1 to 12 is 0.93V, 1.87V, 2.80V, 3.73V, 4.67V, 5.60V, 6.53V, 7.46V, 8.40V, 9.33V, 10.27V and 11.20V, respectively. When the input voltage varies from 160V AC to 270V AC, the DC voltage at the anode of ZD1 also varies accordingly. With input voltage varying from 160V to 270V, the output across filter capacitors C1 and C2 varies from 14.3V to 24.1V approximately. Zener ZD1 is used to drop fixed 12V and apply proportional voltages to all comparator stages (inverting pins). Whenever the voltage at the non-inverting input of the comparators goes high, the LED connected at the output glows. Assemble the circuit on a general purpose PCB such that all the LEDs make a bargraph. In the bargraph, mark LED1 for minimum level of 160V, then LED2 for 170V and so on. Finally, mark LED12 for maximum level of 270V. Now your test gadget is ready to use. For measuring the AC voltage, simply plug the gadget into the mains AC measuring point, press switch S1 and observe the bargraph built around LEDs. Let’s assume that LED1 through LED6 glow. The measured voltage in this case is 220V. Similarly, if all the LEDs glow, it means that the voltage is more than 270V.