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Oscilloscope probes for accurate signal measurements

Oscilloscope Probes Measuring signals with oscilloscopes may be a challenging task especially high-frequency ones. Without proper oscilloscope probes, correct measurement of high-speed time-domain signals wouldn’t be possible. For high-speed measurement, you should consider signal parameters like amplitude, source impedance, rise time and bandwidth. There is a wide variety of probes available – passive, active, current-measurement, optical, high voltage and differential. But let’s narrow discussion to probes used to measure signals with wide bandwidth and short rise times. There are also many variations on what probe is proper. As probes are potential load to measured circuit, it is important to know its sensitivity to resistive, capacitive or inductive loading. Incorrectly chosen probe (like high capacitance) can distort the fast-rising signal. Some circuits may not tolerate probes at all (high-speed amplifiers).

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Reliable soldering with fluxes

Reliable soldering can be achieved by soldering clean surfaces. Usually surfaces are cleaned with abrasives and solvents, but after surface is cleaned surface immediately oxides especially when heated. During oxidation surface is covered by thin oxide film which prevents solder from contacting to metal. This is why flux is used in soldering process. In order to remove/deoxidize surface flux must be applied during soldering. Flux chemically removes surface oxide when heated and makes good metal to solder contact.   (Image source: https://www.tpub.com/neets/book4/12o.htm) There are several categories of soldering fluxes: Acid Flux (or commonly known fluxes: Zinc chloride, hydrochloric, ammoniac); Organic Flux; Rosin Flux. Each flux has their own specifics and may be used for different soldering technologies.

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What is worst-case timing analysis

Probably many of you PC hardware people have faced similar problems when assembling computer from different parts and it seemed to work properly. But under some circumstances system just crashes without any known reason. Even in my practice I had a sound-card that that works well, but time at the time it just crashes and then computer hangs. Of course I can blame drivers or operating system, but there is another probability that there can some timing failures occur. There are lots of complex production around us that may have a number of undefined failures due to lack of timing worst-case analysis. Failures may occur due to power supply fluctuations, thermal changes or other conditions. Worst-case analysis encounter all available information of condition variations that can affect performance of components. Worst-case analysis shows if electronic design meets specifications under variable conditions like temperature, voltage or other variables. Only detailed analysis can prove if design will work reliable under all operating conditions. An it is proved that it is much better to design reliable hardware than fix the problems later. In many ways worst-case analysis may be implemented in various manufacturing phases automatically. By including several simple tests may save lots…

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Chemical effects of electricity

Electronics depend on chemistry more than you can imagine. In order to generate electricity there are many methods used, one of them is chemical. Remember batteries, where electricity is generated because of chemical reactions inside cell. Also in conductors like liquids and gases electricity is carried not by electrons as it is in solid constructions(copper, aluminum, etc.), but by ions – molecules with electric charges. Even non distiled water contain enough ions to be conductive. Lets go through several chemical effects of electricity. Electrolysis Electrolysis is a decomposition of liquid compound by passing electric current through liquid called electrolyte(salt water, copper sulphate, sulphuric acid). Electrolysis is used very widely in industry like electroplating of metals, refining of copper and extraction of aluminum from ore. To make electrolysis happen there are two conductors used cathode(-) and anode(-).  

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How to solder SMD at home even better-Part two

This is continue of part one. Following advises are for how to solder SMD parts with improved technology. Oven isolation As isolation material there can glass insulation be used. In this case glass insulation was packed in aluminum foil: Inspected improvement in heating speed: 0.95% without isolation; 1.50% with isolation only inside oven; 1.72% full isolation.

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How to solder SMD at home-Part one

Soldering SMD parts isn’t hard task and there are many methods of doing this. Lets go through several SMD soldering methods and examples. Method 1 For this you will need: Good eyes or magnifying glass. Better one and another; Soldering iron with small tip ~10W; solder wire with diameter about 0.6mm Steps to follow: cut solder wire in pieces in length of element width:  

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How PCB files are transfered to circuit boards

When you are done with a clean period of task – designing, drawing a circuit, and tracing a PCB, you need to transfer a design to a real board. Here starts what I call a messy part of the design. When designing at home, there are several options – to use prototyping boards or make PCB by yourself. You have to transfer the PCB image to a board with a copper layer in the second option. There are several methods of doing this: direct transfer with glossy paper where the image is printed with a laser printer or more advanced ultraviolet exposure. This way, the PCB image is printed on paper or film directly from the program window without keeping in mind PCB file formats. A different situation is when fabricating professional PCB’s. Each company that fabricates PCB boards always announce what type of file formats they support. So if you are going to order a PCB, better check with them to save your time. The most common and standard format is the so-called Gerber file format. Almost all layout tools can produce Gerber files. If you want to preview your generated Gerber files, there is a nice free Gerber…

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PCB routing considerations

One of the hardest tasks when fabricating PCBs is a Printed Circuit Board(PCB) routing. There are no unified rules on how properly board should be routed, and it would be impossible to write them as the situation on each board is different. One of the general rules is that the shortest routes are the best because longer routes tend to generate more noises or pick them up from different sources. Every conducting material acts as an antenna, no exception with PCB routes. No secret that each route acts as a small transmitting and receiving antenna. So one thing is to keep in mind when routing PCB is to route short as possible. Another concerning area is a cross-talk or cross-coupling between routes. This effect appears when two traces run along with each other, and energy from one trace route couples to another. This effect is obvious in high frequency digital and analog circuits. This effect can make the device dis-functional because only of the cross-coupling effect. These defects are hard to determine as the electrical circuit board is correct. If this effect is noticed – the only solution is to cut traces off and run separate wires instead. It is…

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How does tri-state buffers work

Those who work with microcontrollers probably know about data buses. Only one device(memory, peripherals), that are connected to bus can work at one moment. So only one unit can have direct connection to bus besides CPU which usually is a host. So decoding circuit determines the desired unit and connects it to bus. Other devices are effectively disconnected so that they wouldn’t have any affect to bus operations. They are carried out by tri-state buffers. Tristate buffers allow to isolate circuits from data bus. This means that circuit is switched to high impedance state. Usually we know dual state circuits that can have two logical levels “0” and “1”. But there is also widely used tristate logic, where is ability to switch I/O to high impedance state. Tristate logic can simply be made by two transistors:   Using such circuit we can have following output results according to input variations:   Q1 Q2 Output OFF OFF High Impedance OFF ON 0V ON OFF +5V   Simply speaking when output pin is in high impedance state it is physically disconnected from circuit.  

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Using Gray code for rotary encoders

Gray code is well known and widely used in angular movement systems where angular positions has to be known. Gray code encoder can be constructed pretty easily by masked wheel where tracks are read with photocells.   Did you look at the picture and thought for yourself that gray code is same binary code. Well no… main problem with binary system that using binary code in tracks there are many positions where several tracks change state at same time. This may result in error. Actually in gray code only one track can change at same time during rotation. So then if error occur, the resulting erro will be only one bit. Gray code is easy to convert to binary this task can be done by any microcontroller using a lookup table:     Also you can convert Gray code to binary analytically. To convert from binary to Gray, start at the MSB and compare it to 0. If MSB is equal to0, then write 0 as the MSB for the Gray coded number, otherwise write 1. Next compare the next MSB and compare it to the MSB. If they are equal write a 0 in the position for the Gray…

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