A Primer on Buck (and Boost) Converters

We all know that the reason the electrical system uses alternating current is because it’s easy to step the voltage up and down using a transformer, a feature which just isn’t possible with a DC system… or is it? Perhaps you’ve heard of mysterious DC-DC transformers before but never really wanted to look at the wizardry that makes them possible. Now, SparkFun Director of Engineering [Pete Dokter] has a tutorial which explains how these mysterious devices work.

Known as buck converters if they step the input voltage down and boost converters if they step the voltage up, [Pete] explains how these circuits exploit the properties of an inductor to resist changes in current flow. He goes into exquisite detail to explain how components like transistors or MOSFETs are used to switch the current flow to the inductor very rapidly, and just exactly what happens to the magnetic field which makes these devices possible.

The video gives a good amount of background knowledge if you’ve always wanted to understand these devices a little bit better. There are also a few projects floating around that exploit these devices, such as one that uses an AVR microcontroller to perform the switching for a small circuit, or another that uses the interesting properties of these circuits to follow the I-V curve of a solar panel to help charge a bank of batteries. The possibilities are endless!

Continue reading “A Primer on Buck (and Boost) Converters”

A Low Cost Bench Supply

Everyone needs a power supply on their bench, but a standard lab supply isn’t cheap. [ludzinc]’s PSU Console is a cheap alternative, which provides the basic features you’d expect in a lab supply.

The basis of this PSU is a DC/DC module based on the LM2596 step down switching regulator. These modules cost less than a single LM2596, but have all the required components for a buck DC/DC converter. Sure, they might not last forever, and they’re not the most efficient regulators, but the price is right.

The front panel has four displays for voltage and current, which are just low cost voltmeter displays. The potentiometers are used for adjusting the voltage of the DC/DC, and controlling the current limiter. This limiter monitors current through a shunt, and shuts off a MOSFET when the limit is exceeded.

The final product looks like something that’s ready for daily use, and was much cheaper than most supplies with these features. These low cost DC/DC modules are worth a look if you’re considering a similar build.

Is This Power Supply Bigger Than A Bread Box? No, It Is One.

[newtonn2] must have had food on his mind when he was deciding to embark on a power supply project. The enclosure is quite different…. it is a Bread Box! Even so, flipped up on end we must say it looks pretty cool. [newtonn2’s] previous power supply had crapped out and he needed a replacement supply ASAP, it was a loaf or death situation for this electronics enthusiast.

Similar to a lot of DIY bench power supplies, this one would also be based on an ATX computer power supply. These are good high-current supplies that output voltage in several convenient amounts and in this case are are all routed to their own spring terminals mounted on the enclosure. Even though those standard voltages might be good enough for most, [newtonn2] is extremely kneady and wanted a fully adjustable output so he designed up an adjustable voltage regulation circuit using an LM350 regulator. A volt meter and an amp meter indicates the power being supplied on the adjustable circuit.

Since his last power supply was toast, [newtonn2] wanted this one to be easily repairable. The ATX power supply inside can be replaced in two minutes because nothing is hard wired. The only connections are the ATX connector and power cord. For cooling, holes were drilled in the side of the enclosure so that fans could be installed. This was the yeast he could do to keep the temperature of the interior components down.

In the end [newtonn2] completed his goal of building a pretty unique and functional bench top power supply without spending a lot of dough. Check out his Instructable for extremely detailed build instructions including schematics for how all his components are wired.

Joule Thief Steals Power for a Clock

A common project among electronics tinkerers is the joule thief, a self-oscillating circuit that can “steal” the remaining energy in a battery after the voltage has dropped so low that most devices would stop working. Typically the circuit powers an LED until almost all of the energy is extracted from the battery, but [Lionel Sears] has created a specialized joule theif that uses the “extra” energy to power a clock.

The circuit uses four coils instead of the usual two to extract energy from the battery. The circuit charges a large capacitor which provides the higher current pulses needed to drive the clock’s mechanism. It can power the clock from a single AA battery, and will run until the voltage on the battery is only 0.5 volts.

Normally the clock would stop running well before the voltage drops this low, despite the fact that there’s still a little chemical energy left in the batteries. The circuit can drive the clock for an extended time with a new battery, or could use old “dead” batteries to run the clock for a brief time while the final little bit of energy is drawn from them. If you’re so inclined, you could even use hot and cold water with a joule thief to run your clock! Thanks to [Steven] for the tip.

Hackaday Links, September 14, 2014

Photonicinduction is back! The Brit famous for not setting his attic on fire has built a 20,000 Watt power supply. It connects directly to England’s national grid with huge connectors. Impeccable fabrication and triple servo controlled variacs, and apparently this will be used for making a lot of hydrogen and oxygen through electrolysis of water.

In case you missed it, there’s a group buy for Flir’s Lepton thermal imaging module. Here’s the breakout board.

Need to solder something away from an outlet, and all you have is a disposable lighter? There’s a fix for that.

A Raspberry Pi case designed to be compatible with Lego. Now we need a hat/shield for NXT connectors.

Need another channel in your RC remote? Here’s this. It uses the gyro gain channel on a receiver. If someone wants to figure out how this works, wee do have a rather cool project hosting site.


Here’s something impossibly cool: The Macintosh PowerBop. It’s a Powerbook 170 with the floppy drive replaced with the radio in a cordless phone. It was part of France’s BiBop network, and you could buy private base stations for use at home. It is technically possible to use the radio as a wireless link to a modem, but [Pierre] couldn’t get PPP or a sufficiently ancient browser working. Plus ten points for taking it to an Apple store, and another twenty for trying to connect to our retro edition.

Chicken Lips. [Fran] and our very own [Bil Herd] are hanging out a bunch and recalling [Bil]’s time at Commodore. For this little featurette, [Bil] brought out his very own Commodore LCD. There are three of those in the world. Also included: tales of vertical integration, flipping bits with photons, and 80s era ERC.

Astronaut Or Astronot: Totally Giving Away A Power Supply

Hey! It’s time for another round of Astronaut or Astronot, where we try to give away a jumbo power supply to someone on hackaday.io if they have voted in the most recent community voting round.

Before I get around to telling you who won, we need to go over the criticism of the current voting scheme. There’s a lot of valid criticism out there about how the algorithm that presents projects to the voting page is broken. Yes, it weights projects so some are seen more often than others. And yes, it can be frustrating. However, the results of the voting have no bearing on The Hackaday Prize (the space thing), and the purpose of the entire community voting is to get people looking at the projects, give away t-shirts to the project creators and 3D printers, o-scopes, and power supplies to random people who have voted. We listened to your suggestions and we’re tweaking the algorithm that presents projects for the next round of voting. That starts Monday, we’re doing the drawing on Wednesday, and votes don’t carry over from round to round.

With that out of the way, it’s time to do the whole ‘pick a random person on hackaday.io and see if they voted’ thing. For this week’s lottery, I chose five random people on the site, hoping I wouldn’t go through all of them before giving away a nice bench power supply. The first person, [in3rtial], didn’t vote. You just lost out on a really cool prize there, man.

The second person randomly selected was [tyler]. He voted a total of six times this round. I voted fifty times, but we’re not picky. That means he wins a nice power supply. Everyone go congratulate him for living somewhere that’s cheap to ship a power supply to.

That’s it for this round of Astronaut or Astronot. We’ll have a new round of voting up on Monday. For a change of pace (and because we’re going to be at DEFCON at this time next week), we’re going to do the drawing on Wednesday nevermind, we’re totally doing the drawing from DEFCON. Oh, and if you haven’t, you might want to submit a project to The Hackaday Prize. There’s still time, and your odds of winning something are really, really good.

Overkill Phone Charger, Because, Well, Why Not?

ATX Phone Charger

There are times in a tinkerer’s existence where it is convenient to have the ability to plug in and power a lot of USB devices. Sure, you could use a USB hub but this may not be satisfactory if your devices require a lot of current. A computer may work but is not really a stand alone solution.

[Jeff] and the crew over at Make Lehigh Valley ran into this predicament. They were putting on an Adafruit Trinket class and needed a USB power supply to power all of the Trinkets that were going to be used. As any makerspace would do, they built their own USB Power Station, and the final product is certainly overkill for what they needed (that’s not a bad thing).

An old ATX computer power supply is a logical component to use for this type of project. These power supplies are usually available in abundance and will provide all the amperage any reasonable amount of 5v USB devices can ask for. The 5v output from the ATX power supply was wired to 8 USB jacks. Keeping up with the project’s resourcefulness, those USB jacks were scavenged from a couple of old PCI-slot USB hub panels. Not satisfied with only USB outputs, the guys also wired up some banana jacks so that 3.3, 5 and 12 volts were available for whatever project was being worked on. A 3D printed enclosure keeps everything neat and tidy.

This project used a bunch of recycled parts and solved a problem faced by the group. If you’re interested in using an ATX power supply to make a more bench-top style power supply then check out this build.