Electronics with passion: amplifiers and power supplies, FET's and vacuum tubes..

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:

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.

Soldering MSOP 0.5 mm SMD case

MSOP = Micro-SOP | Micro Small Outline Package SMD = Surface Mount Device [Wiki]
MSOP-10 on the adapter to DIP
[click on the pictures for the real close-up]

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

HotFET Pre: J-FET audio preamplifier parameters and Q&A

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Most of these questions and answers are coming from discussions with friends. Hence the style. Q: Want to see the scope traces, square wave if possible A:

BH delay schematics or let’s minimize relay contacts bouncing

For this article let's accept an axiom that warming up heaters well before raising B+ is a must for any good behaving thermionic valves based equipment.
Picture found on the Net. In case it impairs any copy-rights - please let me know so I can remove it.

HotFET Pre: J-FET audio preamplifier schematics

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At a first glance there's nothing difficult in building a unity-gain preamp: the well known and fairly simple source follower should do the job. However in my case it turned out to be quite an adventure. Why "HotFET" - please refer to this article.
HotFET-Pre (c) - prototyped in a "networking" case
The design is pretty simplistic. There were many calculations, tests and

HotFET Pre: J-FET audio preamplifier (backgrounds)

HotFET Preamplifier prototype assembled in a "networking" case
HotFET Pre - prototype

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The story has begun long ago with the perplexity caused by the fact that amplifiers based on vacuum tubes consume lots of power, get hot and do sound great; while the vast majority of silicon-based audio devices can stay cool and produce somewhat mediocre results. It did not feel right. Hence my attempt to bring some extra controversy into the world of high definition sound reproduction.  

The basic idea of this design

The basic idea of this design was: let's put transistors into the "hot operation mode".

VLC Babyphone: a webcam baby monitor – quick solution

Our baby started to crawl and he did it fast: he would fall from a bed or such before one can hear him. Hearing him crying afterwards was no joy at all, thus an audio-only baby-phone was definitely not a solution. I wanted to get something up very quickly, w/o purchasing extra h/w or spending much time. VLC came at resque. Nevertheless it took me some time to get it right - that's why here's yet another "webcam streaming server how-to". Note: I did it all on Linux machines. But Windows adepts must not be discouraged: VLC runs there very well too, and it's a truly free software! My video-surveillance streaming client-server set-up First of all

Interlocked exchange on Linux: undefined reference to `__sync_add_and_fetch_4′

I am pretty conservative in selecting the tools I use for my projects, thus sticking with good old C++. To be really productive on C++ - using of some sort…