Ultrasound wave propagation and parameters

Ultrasound waves are acoustic pressure waves that interact with propagation media. Ultrasound visualization is typically based on wave reflectance from regions with different acoustic properties. When a wave meets different acoustic media, part of it transmits further while others reflect. This happens due to different acoustic impedance. The ration between reflected and transmitted energy purely depends on the difference in acoustic impedance in both regions. As you can see each material can be characterized by its acoustic impedance Z which is equal to ultrasound speed v and material density r.

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Ultrasound waves and propagation

It is more than 100 years when ultrasound is used for analyzing materials and echolocation. A bit later it was adapted for medical diagnostics. Ultrasound became popular and widespread due to the number of benefits. Probably one of the essential features is that it is non-destructive. The other is simplicity and precision. Of course when we talk about price and simplicity we have X-ray or tomography in mind. Ultrasound can be used in many areas and environments. You can measure geometrical properties of internal structures, physical properties like density, tension. In medical diagnostics, ultrasound is mostly used for visualization of tissues and inner organs. Ultrasound waves and parameters Ultrasound waves are mechanical waves that propagate through media. In solid materials, ultrasound waves propagate faster while in liquids and biological tissues slower (~1400 m/s). In air due to low-density sound waves propagate relatively slowly (~340 m/s). Ultrasound speed depends on temperature and pressure.

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Benefits of using multiturn potentiometers

Potentiometers are common electronics components that convert rotary or linear motion in to change of resistance. They can be found anywhere where some adjustments are needed, volume control and joysticks. You can dive into the long theory about potentiometers how they are made, what materials are used and what output characteristics they have regarding rotation angle. As electronics hobbyist and probably pro you usually deal with two common types of potentiometers – standard pots with knobs and trim potentiometers. The first group of potentiometers is used where the user has to access potentiometer when he needs to change one or another parameter like sound volume or screen brightness. They usually are more prominent in size and can be mounted vertically or horizontally to board. Also, they have a panel mount with the nut. This type of potentiometers needs to be mechanically stronger and resistive material more durable due to frequent use.

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Building simple constant current power LED driver

Usually, when we need to drive low power LEDs, we don’t care much about power losses. What we do we add a current limiting resistor, and that’s enough. For instance for 20mA LED we choose between 300Ω-1kΩ resistor when powering from 5V. But a different situation is with power LEDs. The currents are much more prominent here like 1A and more. Adding a resistor to limit the current isn’t an option, because power losses become significant. Here you need a constant current driver to drive it safely without wasting energy. It happens that I have Cree XR-E Q5 XLAPM-7090 LED lying around. It requires 3.7V driving voltage and can take up to 1A current. There are several light intensities given at specific currents:

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Driving LEDs – things everyone needs to know

Light Emitting Diodes more frequently known as LEDs are semiconductor devices that convert electricity into light. It was hard to find a gadget or other device that doesn’t use LEDs. They are cheap; they are simple to use, and they are small. LEDs can emit different light color depending on different chemical compound material in a semiconductor. LED symbol One and universal LED symbol is as standard diodes but with couple arrows indicating that it emits light:

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Zener – one diode for many uses

Zener diodes are specially designed diodes (heavily doped) that have low reverse voltage breakdown. Due to this characteristic zener diodes are connected backward to normal operation. If zener is forward biased, it acts as a regular diode with a forward voltage drop at 0.6V. Zener diode backward voltage breakdowns may range from 2.4V up to 100V. Honestly speaking if you need like 1.2V then probably you need to connect two forward biased diodes in series for 0.6V+0.6V = 1.2V drop.

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Diodes – how to choose one

Diodes are semiconductor devices commonly used for many purposes. In general, you can imagine diode to be a valve that passes current to one direction and stops it to flow back. The first thing that comes in mind – this might be a good choice for reverse voltage protection, but. In reality, things are a bit different. First of all, diodes aren’t perfect devices. They have a so-called forward voltage drop which is about 0.7V for standard diodes. So if insert diode into the power supply, say 5V the after protection you will get 4.3V where part of voltage is lost in the diode. If you want to go this way – better choose Schottky diode instead which has a smaller forward voltage drop. A forward voltage drop occurs when the diode is forward biased what means current flow from anode to the cathode.

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