Thermoelectric devices are seen very often in various appliances. Small refrigerators, semiconductor chip coolers, medical chillers. Thermoelectric effect works in both directions – it can generate temperature difference when current flows or it can generate current when temperature difference is applied.
About thermoelectric effect
It is known for more than 100 years. There are several scientists who discovered this effect in one or another way. Probably you’ve heard Peltier effect. Jean Charles Athanase Peltier discovered that if you apply electrical current to junction of two materials it gets cold or hot (depending on current direction). (more…)
Probably you are already familiar with famous DS1052E hack where guys were able to double and even triple bandwidth. It happens that on my table is DS1022CD scope with 25MHz analog bandwidth. And this hack doesn’t apply to my model. We all know that same series Rigol oscilloscope models tend to have same hardware weather they are 25MHz, 50MHz or 100MHz analog bandwidth. Of course sampling rate (400MHz) stays the same. So it all lies in software. I felt that someone will figure out how to do this with this pretty old oscilloscope. And here it is – a hackaday pointed to a great news – simple way of changing model from DS1022CD to DS1102CD which converts analog bandwidth from 25MHz to 100MHz. This is quite a step without spending a penny.
Touch screen technology has been on the market for a while now – specifically for gaming devices – although it’s only in the last 10 years that this translated to mobile technology. It has boosted online gaming numbers because of the ease of use on mobile phones; but how exactly has touch screen technology improved?
The main type of touch screen currently used in mobile technology (especially the iPhone) is a capacitive screen; these work with anything that holds an electrical charge – including human skin. They’re made up of materials that hold charges in an electrostatic grid of either a surface or projective screen. Resistive screens are analogue devices that create a connection between two flexible resistive screens. They use the pressure of your finger to create a change in the flow of electricity; when a finger is placed on the mobile, a voltage drop is registered that allows the screen to work. (more…)
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: (more…)