Dec 28

Using MOSFET for reversed power polarity protection

Reversed power protection using N-channel MOSFET

Trivial topic indeed: why one would ever need to protect a circuit from a rolled-over power supply? There are countless potentials for mistakes that can result in an electronic developer pulling out his hairs and staring at his design worth of many hours or days of work - the one that he bricked just a moment ago.

 

To name just a few:

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Dec 26

DIY Galvanically Isolated Solid State Relay for mains power controlled by 5..20mA current loop

Many of articles on this site might look trivial. So they are. But this is the result of my personal experience: I got tired catching myself re-inventing the wheel again and again. Thus I decided to post whatever proved to be useful for me at least once, in the hope that it might save some time to myself and others in the future.The industry makes it all for you. One can purchase a Solid State Relay (SSR) that would fulfill virtually any imaginable requirements. The only question is money: a decent device capable of handling mains power load of few hundred Watts would cost as from $10 and up. While if we lower the bar and look for an SSR capable of switching say 100mA - it would be possible to get one for less than a dollar.Here is a very simplistic (and relatively inexpensive) SSR implementation that is capable of managing heavy loads. It uses a TRIACas the main power switch and a "telephony" SSR controlling it. Continue reading

Dec 04

Compliant Constant-Current Source (c) TCJ

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Somehow CCS implementations became a theme of the year 2011 for me. This little scribble is here just to make sure I do not forget a nice topology I came across. Apparently this one has been invented by someone else, not me.Here's the original source where I saw it for the first time: Tube CAD Journal' blog entry from 15 November 2011.

Shadow Constant-Current Source a.k.a. "Compliant CCS" by John Broskie

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