Build The Simplest Bipolar Power Supply

October 29, 2016 by Elliot Williams 46 Comments

How many integrated circuits do you need to build up a power supply that’ll convert mains AC into a stable DC voltage? Would you believe, none? We just watched this video by [The Current Source] (embedded below), where he builds exactly that. If you’re in the mood for a very well done review of diode bridges as well as half- and full-wave rectifiers, you should check it out.

First off, [TCS] goes through the basics of rectification, and demonstrates very nicely on the oscilloscope how increasing capacitance on the output smooths out the ripple. (Hint: more is better.) And then it’s off to build. The end result is a very simple unregulated power supply — just a diode bridge with some capacitors on the output — but by using really big capacitors he gets down into the few-millivolt range for ripple into a constant load.

The output voltage of this circuit will depend on the average current drawn, but for basically static loads this circuit should work well enough, and the simplicity of just tossing gigantic capacitors at the problem is alluring. (We would toss in a linear regulator somewhere.)

Quibbling over circuit designs isn’t why you’re watching this video, though. It’s because you want to learn something. Check out the rest of his videos as well. [TCS] has only been at it a little while, but it looks like this is going to be a channel to watch.

https://www.youtube.com/watch?v=0iDCsrMM7M0

A Quick History Of The Battery

October 29, 2016 by Gerrit Coetzee 36 Comments

[Colin] tells us it all started with [Benjamin Franklin]’s battery of capacitors. It was a bunch of leyden jars hooked together in series and there wasn’t even chemistry involved yet, but the nomenclature stuck and it wasn’t long before it evolved into the word we use today.

For the word to change, things got chemical. [Alessandro Volta] introduces his voltaic pile. Once scientists latched onto the idea of a stable reaction giving a steady stream of magic pixies for them to play with, it wasn’t long before the great minds were turning their attention to improving this new technology.

In the classic game of one-upmanship loved by technical people all over, we quickly skip forward to the modern era. An era where no man is unburdened with the full weight of constant communication. It’s all thanks to a technology that’s theoretically unchanged from that first pile. Video after the break.

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Try Not To Look At This Giant Plasma Tube

October 28, 2016 by Manuel Rodriguez-Achach 18 Comments

Everybody loves plasma globes, but if you are like [zrgzhv], building them as large as possible is the challenge! Definitely a beautiful project, at 7 feet long and 1 foot in diameter, this monster tube makes an impressive display of plasma filaments that slowly move inside. Heck, they almost seem to be alive following the movements of his hand and it’s hard not to become mesmerized by the motion.

This tube follows the same principle of operation as its smaller cousin, the plasma globe. Air is evacuated and the tube is filled with a mixture of noble gases, with the particular mixture being responsible for the color of the filaments. Then, high voltage AC is applied to an electrode, which causes the moving tendrils of colored light to extend from the electrode to the outer glass, a phenomenon known as glow discharge. In general, gas-filled tubes can have other uses such as lightning — in the form of fluorescent, neon and xenon lamps — or high power switching as in the thyratron tube, among other applications.

The tube has a weight of over 65 pounds, and needs 300 watts of power to operate from an also homemade power supply. In another video, you can see 10 tubes of different colors working at once. Plasma always makes a great attention-getter; another nice example of its use can be seen in this steampunk lamp which incorporates rotating contacts on the outside of the glass.

Battery Powered Fog Machine Just In Time For Halloween

October 27, 2016 by Gerrit Coetzee 31 Comments

[makendo] needed a portable fog machine for an upcoming project. It seemed like the kind of a thing a liberal application of money on the Internet could fix in no time. But quality fog machines are too expensive, and the cheap machines are just, well, cheap. Stuck between $800 and quickly broken crap, he decided instead to fashion his own.

Fortunately for him, a recent fad has made it so that a certain segment of the populace absolutely require dramatic clouds of scented drug fog or they get cranky. The market saw an opportunity, cost optimized, and now there are many portable fog machines just waiting to be born in the form of an e-cigarette. However, an e-cigarette needs interaction from a person’s lungs to provide an annoying cloud. So he modeled up a 3D printable case that would blow air into the intake of the e-cigarette. Instead of filling a person’s lungs with a cloud of eye drops and nicotine, it would let out a steady stream of fog.

This device does burn through emitters, because the e-cigarette was not designed for this kind of heavy duty. Even reading the Amazon comments for the $800 dollar version, this is fairly normal for these things. So now [makendo] is able to produce a nice cloud of smoke whenever he needs and it only set him back around $40 US dollars.

A Short Introduction To Staking And Potting

October 27, 2016 by Gerrit Coetzee 41 Comments

Staking and potting are not often used in the hobby electronics world, not really entering to the common vernacular. However, everyone who’s ever busted out a glue-gun to convince that dang wire that keeps coming loose to stay has done it.

However, as [Sean Thomas] touches on, staking is not necessarily as easy as a dob of hot glue. There is a method to the madness. [Sean] gives some examples in pictures, but also directs people to the excellent NASA standard methods for staking. It’s surprising how many unintuitive caveats there are to the proper technique.

Potting, or covering everything in epoxy forever, is a great way to get a waterproof, unserviceable, and practically mechanically invincible circuit. The big challenge in potting is picking the right material. A soft silicone, for example, might transfer an unexpected force to an unexpected section of the circuit and cause a mechanical failure. A nice hard epoxy may be too insulating and cause a thermal failure. The standard RTV from the big box store has acetic acid that will eat your components.

These two techniques that come in handy when you need them and worth the bit of reading it takes to get familiar. Have you used either in your own workshop? Let us know the application and the material/techniques you have tried in the comments below.

A Spreadsheet For Guesswork

October 25, 2016 by Gerrit Coetzee 9 Comments

Ever wish you could guess more precisely? Or maybe just make your guesses look confusingly legitimate? Guesstimate could help.

It uses Monte Carlo simulations to add some legitimacy to the ranges given to it. For example, if you say the cost of lumber for your next project could be between 2 and 8 dollars a piece, you don’t typically mean that it’s equally likely to be any of those numbers. Most people mean that the boards are most likely to be around 3-5 dollars and everything lower or higher is less probable. Using different shaped distributions, Guesstimate can help include this discrepancy of thought into your pseudo-calculations.

It’s a neat bit of code with a nice interface. There is a commercial side to the project for those who want to collaborate openly or pay someone to host it privately. It has a few neat example models for those interested.

Does anyone use anything like this in their daily lives? Is there another similar project out there? This kind of thing is pretty cool!

What Does ESD Do To My Circuit And How Can I Protect Against It?

October 25, 2016 by Gerrit Coetzee 35 Comments

[Kevin Darrah] is risking the nerves on his index finger to learn about ESD protection. Armed with a white pair of socks, a microfiber couch, and a nylon carpet, like a wizard from a book he summons electricity from his very hands (after a shuffle around the house). His energy focused on a sacrificial 2N7000 small signal MOSFET.

So what happens to a circuit when you shock it? Does it instantly die in a dramatic movie fashion: smoke billowing towards the roof, sirens in the distance? [Kevin] set up a simple circuit to show the truth. It’s got a button, a MOSFET, an LED, and some vitamins. When you press the button the light turns off.

He shuffles a bit, and with a mini thunderclap, electrocutes the MOSFET. After the discharge the MOSFET doesn’t turn the light off all the way. A shocking development.

So how does one protect against these dark energies out to destroy a circuit. Energies that can seemingly be summoned by anyone with a Walmart gift card? How does someone clamp down on this evil?

[Kevin] shows us how two diodes and a resistor can be used to shunt the high voltage from the electrostatic discharge away from the sensitive components. He also experimentally verifies and elucidates on the purpose of each. The resistor does nothing by itself, it’s there to protect the diodes. The diodes are there to protect the MOSFET.

In the end he had a circuit that could withstand the most vigorous shuffling, cotton socks against nylon carpeting, across his floor. It could withstand the mighty electric charge that only a grown man jumping on his couch can summon. Powerful magics indeed. Video after the break.

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