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The Mystery of USB Chargers

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By  Jestine Yong  on July 9, 2014 Almost any new device such as mobile phone, tablet, iPod, GPS etc… will come with some sort of USB Charger and a cable. The cable will connect to your device through a dedicated connector, mini USB, micro USB or manufacturer’s specific. At the other end, most cables will be terminated with the familiar USB connector (USB type A), which you can connect either to the charger or to your computer. If you are like the 50% of mobile phone users you will buy a second charger, just to have one at work and one at home. Over the years, you will end up with several USB chargers and you might wonder if you could simplify your life by having only one charger, or at least a couple of chargers, for all your devices. The problem is that they are not all compatible. Your Samsung charger will not work with your Apple device etc… In this article we will analyze some USB chargers and find out why they are so different. And may be find out that they are ...
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Programação de um CLP: Modos de programação

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No seguimento do curso de Automação, neste artigo apresento como perceber os conceitos básicos de programação de um CLP. No decorrer das próximas edições apresentaremos a forma de programar um controlador lógico programável Autores: Filipe Pereira - Eng. Elétrotécnico / Automação Klean Energie 4 Life, Ltda Energias Renováveis - Portugal As linguagens de programação são empregadas nos CLPs desde que estes surgiram em 1960. Estas permitem ao usuário inserir programas de controle utilizando sintaxes pré-estabelecidas. Previamente ao estudo dos três tipos de linguagem mais utilizados na programação de CLPs, convém rever alguns conceitos essenciais. O programa que vai definir o automatismo é constituído por uma série de instruções e funções onde são operados os bits de memória. Estas instruções e funções, serão introduzidas na memória do CLP, através de um periférico destinado a esse fim e que poderá ser uma console de programação ou software específico para PC. Veja na figura 1 u...
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Subwoofer Repair

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By  Jestine Yong  on December 3, 2013   A customer brought this powered speaker for repair. It is a Wharfedale Titan 12’ subwoofer Amplifier. The complaint: No power. I opened the unit checking the usual things such as the fuse, EMI filter coils, voltage on filter caps etc. These all checked out fine, and I measured 320VDC over the two filter caps. The unit uses a SMPS. The smps and class-D Amplifier, are both on the same board. I then connected my analog meter to one of the secondary output lines going to the amplifier. There was no voltage here, and nothing on any of the other output lines going to the pre-amp board. I then proceeded to check if it is a shutdown problem, by switching the unit on and watching to see if the needle on my analog meter jumps up for a brief moment. No movement at all. This made me believe I have a primary –side fault. I checked the two, main switching Mosfets  and they were good. From the below photo you can ...
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