Archive for the ‘Electronics Design’ Category

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Extremely simple stepper driver circuit

Wednesday, February 3rd, 2010

The normal way to drive a stepper motor is to use switched-dc voltages to energize the stepper motor coils one by one after each other. But a stepper motor will run off ac lines if you introduce a 90° phase shift between the voltages applied to the motor’s two windings. The extremely simple circuit in Fig 1 drives a stepper motor directly from 12V ac , 60 Hz power supply. Four steps equal one ac cycle.

1cmpdrv1

I tested the circuit idea with a slightly different setup and it worked well. I just picked a random small stepper motor I had lying around. It had around 90 ohm coil resistance. I used a 10 uF capacitor (a small electrolytic, dry capacitor would be better for long run). The power source I used was 24V 50Hz AC. The stepper motor run with the circuit nicely at least the short time I tried it. I did not run it for a long time because I did not know the specifications of the stepper motor, and I feared that the 24V AC could be too high for it (could cause overheating on long run).

Posted in Electronics Design, diy | 5 Comments »

Differential video amplifiers

Thursday, January 28th, 2010

Differential amplifier approach uses an operational Amplifier. Operational Amplifiers only amplify the difference between the two input lines. This method eliminates common mode noise between the incoming signals by making A-B=C, as only the difference between A & B are amplified. Operational amplifiers is maintain wide bandwidth signals throughout your system while eliminating ground loop problems that are caused by power and video. Differential video amplifier inputs are used in some video equipments (typically some video projectors) and video distribution amplifiers to fight against ground loop problems.

Differential video amplifiers have a limitation on their input voltage range which gives some limitations how much common mode signal those circuits can tolerate. If the ground potential difference is more than few volts, then operational amplifier based isolators don’t work effectively. Too high voltage difference can cause problems from very distorted video signal to damaged differential video amplifier. If the voltage difference is a substantial proportion of the DC supply voltage of the amplifier, you will probably have trouble using an amplifier alone.

It is a good idea to measure the voltage difference before using differential video amplifiers to be sure not to damage them. Measuring can be done using a multi-meter (check using both AC and DC ranges) or better using a scope earthed to the mains supply, and put the probe on the earth connection of the incoming video cable. If you many potential difference which are many volts, then you have quite probably something wrong in the grounding of the building and you should consult a qualified electrician to check and correct this potentially a dangerous problem

09D20241

Image source: http://www.edn.com/archives/1997/050897/10di_06.htm#Figure%201

Look also: http://pdf1.alldatasheet.co.kr/datasheet-pdf/view/136144/MAXIM/MAX9546.html

Posted in Audio and Video, Electronics Design, Groundloop | 6 Comments »

Smartphone component costs

Tuesday, January 12th, 2010

How much does the components that make a smartphone cost? iSuppli has analyzed over the years the cost of the components to make several cellular phones and other electronics gadgets. Interesting reading always when you get your hand to this material.

Nexus One is the new HTC Phone, with a Goggle name on it, with the newest Android Software, and powerful hardware inside. Nexus One’s hardware estimated to cost $175 article tells that Google’s forthcoming Nexus One smartphone is composed of components worth about $175, according to a tear-down conducted by iSuppli. That price is just for components, it does not include other expenses such as manufacturing, packaging, and software. The cost of the raw ingredients of a phone does not take into account the R&D, design and testing that must happen. And there is always the marking costs.

One very interesting part of the article is the table that lists the complete list of hardware in the Nexus One, including the prices for different components. This is interesting reading for everybody interested in what is inside this gadget. The most expensive component is Qualcomm’s 1GHz Snapdragon processor ($30.50). It runs the Google’s Android 2.1 operating system.

So it looks like the cost of making the phone is about the same as the iPhone 3G S ($178.96 BOM). Nexus pricing is not so different from the iPhone, so margins for the phone as Apple is famous for high margins.Those are the normal industry margins for high end smartphones when they are new. When the models get older, the prices tend to drop and margins fall unless the manufacturing is optimized. Just for reference check this Nokia N79 Eco Mobile Phone terdowns.

nexusone

Image source: Nexus One: “Web meets phone” video

Posted in Electronics Design, Products, Telecom and Networking | 9 Comments »

EDN microprocessor/microcontroller directory

Monday, January 11th, 2010

There are so many processor options for embedded-system applications that it is easy to miss the perfect fit just because you do not know it even exists. EDN microprocessor/microcontroller directory has kept electronics designers up to date on available microprocessors/microcontrollers for 36 years. You have access a wealth of information on more than 70 vendors and hundreds of microprocessor and microcontroller devices and cores. Very useful information tables deliver technical specifications including operating frequency, memory details, core voltages, power consumption, timers, I/O, packaging, and price. The master table details nearly 1000 devices/cores.

Posted in Electronics Design | 2 Comments »

The anatomy of a modern audio-video amplifier

Wednesday, December 30th, 2009

A modern Audio-Video amplifier/receiver (AVR) is an exceedingly complex piece of consumer electronics, requiring expertise in many aspects of analogue and digital audio and high definition video, plus considerable software skills. ‘The anatomy of a modern audio-video amplifier’ lecture by John Dawson from Arcam for Audio Engineering Society UK is an interesting talk on engineering related to home theater amplifiers. This lecture takes a look inside the Arcam AVR600 (one of the few such units developed outside of the large Japanese consumer electronics companies) and will discuss some of the design choices made in order to try to ensure a good chance of commercial success. You can download the lecture in MP3 format.

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The main points in talk are that designing a home theater amplifier is a paradox. The amplifier should be cheap to sell well. On the other hand it should be expensive to be well made (it is a very complex device). The amplifier should be designed quickly (so that it is not outdated when comes to quickly changing markets) but the design should be free of bugs. The amplifier should have all the newest features in it, but it should also be as simple as possible to sound good and be easy to use.

ArcamAVT600back

Image source: Arcam AVR600 web page

Posted in Audio and Video, Electronics Design, Products | 32 Comments »

Understanding instumentation amplifiers

Sunday, December 6th, 2009

An instrumentation amplifier is a type of differential amplifier that has been outfitted with input buffers, which eliminate the need for input impedance matching and thus make the amplifier particularly suitable for use in measurement and test equipment. The ideal common-mode gain of an instrumentation amplifier is zero, which means that it is a very good at rejecting common mode voltages (typically noise from various sources including ground loops).

Although the instrumentation amplifier is usually shown schematically identical to a standard op-amp, the electronic instrumentation amp is almost always internally composed of 3 op-amps. The three-op-amp instrumentation amplifier is seemingly a simple configuration in that it uses a basic, decades-old operational amplifier to gain a differential input signal. Instrumentation amplifiers can be built with individual op-amps and precision resistors, but are also available in integrated circuit form from several manufacturers.

EDN Magazine article Understanding CMR and instrumentation amplifiers tells that from the CMR (common-mode rejection) perspective, instrumentation amplifiers are systems in which various parts contribute to the CMR error at different system gains. his situation is not so mysterious when you think about the inside of this device. And the inside operation of the instrumentation amplifier is well presented on this article.

200px-Op-Amp_Instrumentation_Amplifier.svg

Posted in Electronics Design, Groundloop | 3 Comments »

Ground loop common-mode compensation

Thursday, December 3rd, 2009

Ground loops affect video signals. Understand them, then deal with them. When designing or installing the cables for a video transmission system, one assumption that engineers commonly make is that the local earth grounds of both ends of the cable are the same. When circumstances don’t support this assumption, the video performance can exhibit gross distortions.
Solve ground loop problems in long-distance video transmission article looks at the situations in which ground may have a non-zero potential, and reviews the basic options for grounding connectivity. Finally, it shows a solution that ensures quality video transmission, even when any ground-potential differences are present. This article shows a common-mode compensation for differential transmission lines.

C0085-Figure1

Posted in Audio and Video, Electronics Design, Groundloop | 4 Comments »

Survival Between Microphone and Voice Coil

Monday, October 12th, 2009

An EE’s Guide to Survival Between Microphone and Voice Coil is an interesting  slide set amde by Netherlands´ well known audio engineer Bruno Putzeys and put to web by Hypex Electronics and Grimm Audio. It was presented in AES convention at 2007. It is a very good presentation of the whole audio electronics path from microphone to speaker. If you are into audio electronics, read this slide set.

Slide4s

Posted in Audio and Video, Electronics Design | 8 Comments »

Use right ground symbol

Thursday, October 8th, 2009

Use right ground symbol in your electronics schematics and other drawings.

Earth-ground symbol represents a real connection to earth. That connection could be for example 10-foot-high copper-clad steel bar driven into the earth (at your premises or nearby provided by power company) or metal water lines. That earth ground is wired to the neutral of your house wiring at the breaker panel. You can reasonably use the earth-ground symbol for the ground pin on the electrical outlet. Your electronics equipment schematic should use the earth-ground symbol to indicate connection to the electrical outlet ground pin on equipment plugged to wall outlet.

It is bad practice to use earth-ground symbols for chassis common. You an use the chassis common wherever a power supply or circuit card connects to the chassis. In a circuit board schematic you can use chassis symbol when a standoff screws the PCB to the chassis.

Signal-ground symbols are most suitable for most circuitry on a PCB. A design can have several of these symbols, with notations to identify them.

Information source: EDN magazine article Draw the line: Isolation shields systems from shocking surprises

groundsymbols

Posted in Electronics Design, Groundloop | 7 Comments »

Build a Ground Loop Detector

Thursday, September 24th, 2009

Ground loops are a common problem in many experimental setups. A ground loop is an un-
wanted closed loop of cables in the setup, most often through the ground system. Those ground loops are often hard to find and debug. A Ground Loop Detector document describes how to build and test a simple system to detect ground loops in experimental setups. The two circuits used are from article “Simple system for locating ground loops” by P. M. Bellan. The ideas used on those articles are used in commercial product Loop Slooth. The idea in those circuits is to induce the test signal (100 kHz) into the ground system and then detect the amplitude of that signal in different parts of the setup with help of Rogowski coil based detector circuit. The basic idea in this circuit looks very promising. I have not yet tested the presented circuits, but at some laboratory tests the basic idea behind this circuit seems to work.

Gndloopexciter

Gndloopdetector

Posted in Electronics Design, Groundloop, Products, diy | 45 Comments »

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