Emergency supply source for your electronic device

Sometimes you are needed to maintain power supply for your device for some time when the main source fails. It can be alarm system or some light source or digital clock. Of course if source interrupts are very short, there can be capacitor with big capacity connected, but it is not reliable. Better use backup battery and diode. This solution is very simple and cheap. The diode protects the back current float to battery. This doesn’t take much space to implement as the main bigger part is battery. As there just backup source it is not necessary to use rechargeable battery.

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Physiological system modeling

Most of physical and chemical experiments can be described with a finite number of rules. In physiological processes everything can be tied to laws of nature. Good model can be as a guideline to new experiments. Usually model and experiment has iterative connection. In order to understand ho to investigate any material there is model needed (block 1). First we need abstract understanding about what we are investigating (block 2). Abstracts are transformed into mathematical model (block 3). There we can use formulas and solve them using computer. The results you get shows, what experiments have to be done and what to expect from them. This loop system is resistive to irregularities in mathematical model. In other words, this is the purifier of experiments and models. How to model blood vessels There can be many modeling ways of them. This is because, that every model has its own benefits and…

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CMOS and TTL compliance

There was a time, when all IC’s were only TTL type. They were marked as 74LS or 74ALS. But then there came CMOS types of semiconductor. They are usually marked CDxx. And lately there appeared combined semiconductors who are compliant to both types. They usually are marked as 74HC or 74HCT. TTL are faster than CMOS, but they sink more power. They are powered from 5V source. To diminish the power consumption, the CMOS were developed. They can work with supplied voltages in range 3 to 15V. The main disadvantage is that they are static sensitive. So you always have to be grounded when working with CMOS. Now both types of semiconductors are widely used. Sometimes there is as dilemma to connect TTL to CMOS. You cannot connect directly TTL to CMOS as there are different supply voltages. So you need some compliance circuit. The simplest can be bipolar transistor…

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Skin lession boundary tracing algorithm

I found a Matlab to be a convenient tool which allows easily to trace boundaries of objects in a picture. So I adopted it to skin lesions. This can be used for automatic detection of skin irregularities and utilized to calculate lesion properties like the asymmetry of shape, or border irregularities, who can help in detecting melanoma. There are numerous investigations done, so I only put a few examples of how it looks. I will give you my source code so that you can try it on your own. Look at my results: 1) And it also finds the center of mass:

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Skin imaging methods for melanoma diagnosis

There are many skin image capture methodologies developed and used. Here is a short review of them: Dermatoscopic photography The deepest layer of skin can be reached – Papillary dermis Resolution – depends on the optical system View of skin – Horizontal The main disadvantage is reflections of light from skin surface – stratum cornea.   Dermatoscopic oil immersion photography The deepest layer of skin can be reached – Papillary dermis Resolution – depends on the optical system View of skin – Horizontal Reflections of light from skin surface are smaller because of oil used between camera optics and skin.

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Polarizer test

I used simple lamp directed to glossy table surface. One polarizer is in front of lamp and other is in front of lens of digital camera. Both polarizes are perpendicularly oriented to each other. How does this work? There is a theory about an angle on which the incident polarized electromagnetic waves turn reflects from surface with polarization plane turned in 90 degrees. When light going through polarizer towards the surface, the light is polarized in one direction and when it reflects from surface it is turned by 90 degrees and those waves are filtered by another perpendicular polarizer in front of lens.

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Removing 60Hz from ECG using digital band stop filter

Let’s make a filter, which filters off the 60Hz frequency from ECG signal. As we know American power supply is 60Hz. This is common noise in biomedical signals, while they are powered from industrial power supply. This type of noise can be defined easily and can be filtered as parameters of noise are known. Here is one example of how to implement FIR filter using mathematical tools, like Matlab. This can be done by using microcontroller, like ARM or even ARM, because the frequencies are up to 1 KHz. Initial conditions: f0=60Hz – pover supply frequency; fs=500Hz – sampling rate; frequencies who define complex zeros: we get w0=0.754; Positions of complex zeros: Zeros and poles in z plane System Function From it we can calculate filter coefficients: And filter coefficients:         Also we know that: And here we get filter characteristics: We have band stop filter at 60Hz and…

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