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 in to long theory about potentiometers how they are made, what materials are used and what output characteristics they have regarding to rotation angle. As electronics hobbyist and probably pro you usually deal with two common types of potentiometers – basic pots with knobs and trim pots. First group of potentiometers are used where user has to access potentiometer when he needs to change one or another parameter like sound volume or screen brightness. They normally are bigger in size and can be mounted vertically or horizontally to board. Also they have a panel mount with 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

Normally 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 different situation is with power LEDs. The currents are much bigger here like 1A and more. Adding 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 converts electricity in to light. It hard to fond a gadget or other device that doesn’t use LED diodes. 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 common 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 backwards to normal operation. If zener is forward biased it acts as regular diode with forward voltage drop at 0.6V. Zener diod backward voltage breakdowns may range from 2.4V up to 100V. Truly 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 generally you can imagine diode to be a valve that passes current to one direction and stops it to flow back. First thing that comes in mind – this might be a good choice for reverse voltage protection. In fact they are. But… In reality things are a bit different. First of all diodes aren’t perfect devices. They have so called forward voltage drop which is about 0.7V for standard diodes. So if insert diode in to power supply, say 5V the after protection you will get 4.3V where part of voltage is lost in diode. If you wanna go this way – better choose Schottky diode instead which has a smaller forward voltage drop. Forward voltage drop occurs when diode is forward biased what means current flow from anode to cathode.

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Thoughts on interfacing piezo vibration sensor

piezo vibration sensor test with oscilloscope

Some time ago I purchased a MiniSense 100 Vibration sensor. Probably had some project in mind, but it happened that it dived in to drawer among other “to do” things.  I thought it’s time to try few things with it. Piezo sensor MiniSense 100 is very sensitive with pretty good frequency response and is linear (±1%). As you can see high sensitivity is achieved with 0.3 gram inertial mass at the end of film. As there is a hole in the mass you probably can screw in additional mass and thus increase sensitivity even further. Probably there is no need to explain where such sensor would be useful. These could be vibration/ motion sensors, impact sensors and other areas where motion and acceleration is involved. Normally sensitivity is 1V/g. Where g is standard gravity or also known as standard acceleration due to free fall and is equal to 9.80665m/s2. As…

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Building simple power supply from theory to working example

Power supply is essential part in every electronic device. The whole system relies on it. If power supply fails – device dies too and there is a chance that sensitive parts may be damaged. Power supply solutions vary from device to device. They may work using different techniques depending on needs. Tim have described probably simplest power supply solution which converts Alternating Current (AC) to Direct Current (DC). Supply circuit consists of well known parts that are – transformer, which transforms voltage from 230V AC to 12VAC, them follows diode bridge rectifier, smoothing using large caps and regulation with standard 7805 voltage regulator. Such solution proved itself in many designs. Its simple, cheap and builds fast. Tim put everything in short and informative post without overhead information. Following it you will be able to build 5V DC power supply in an hour.

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