dc-dc

23 Articles

Cordless Tool Battery Pack Turned Into Portable Bench Supply

March 24, 2018 by 18 Comments

Say what you want about the current crop of mass-marketed consumer-grade cordless tools, but they’ve got one thing going for them — they’re cheap. Cheap enough, in fact, that they offer a lot of hacking opportunities, like this portable bench power supply that rides atop a Ryobi battery.

Like many of the more common bench supply builds we’ve seen,  [Pat K]’s more portable project relies on the ubiquitous DPS5005 power supply module, obtained from the usual sources. [Pat K] doesn’t get into specifics on performance, but supplied with 18 volts from a Ryobi One+ battery, the DC-DC programmable module should be able to do up to about 16 volts. Mating the battery to the supply is easy with the 3D-printed case, which has a socket for the battery that mimics the sockets on tools from the Ryobi line. It’s simple and effective, as well as neatly executed. The files for the case are on Thingiverse; sadly, only an STL file is included, so if you want to support another brand’s batteries, you’ll have to roll your own.

Check out some of the other power supplies we’ve featured that use the DPS5005 and its cousins, like this nice bench unit. We’ve also covered some of the more hackable aspects of this module, such as an open-source firmware replacement.

A DIY 5V-3V Switching Converter In The Space Of A TO-220 Package

March 13, 2018 by 33 Comments

We’re suckers for miniaturization projects. Stuff anything into a small enough package and you’ve probably got our attention. Make that something both tiny and useful, like this 5-volt to 3.3-volt converter in a TO-220 sized package, and that’s something to get excited about. It’s a switch mode power supply that takes the same space as a traditional linear regulator.

Granted, the heavy lifting in [Kevin Hubbard]’s diminutive buck converter is done by a PAM2305 DC-DC step-down converter chip which needs only a few supporting components. But the engineering [Kevin] put into this to squeeze everything onto a scrap of PCB 9-mm on a side is impressive. The largest passive on the board is the inductor in 0805. Everything else is in 0603, so you’ll be putting your SMD soldering skills to the test if you decide to make this. Check the video after the break for a speedrun through the hand soldering process.

The total BOM including the open-source PCB only runs a buck or two, and the end result is a supply with steady 750-mA output that can handle a 1-A surge for five seconds. We wonder if a small heatsink tab might not help that; along with some black epoxy potting, it would at least complete the TO-220 look.

[Kevin]’s Black Mesa Labs has a history of turning out interesting projects, from a legit video card for Arduino to a 100-watt hotplate for reflow work that’s the size of a silver dollar. We’re looking forward to whatever’s next — assuming we can see it.

Continue reading “A DIY 5V-3V Switching Converter In The Space Of A TO-220 Package” →

Cleaning Up A Low-Cost Buck-Boost Supply

October 10, 2017 by 25 Comments

Cheap DC-DC converters have been a boon on the hobbyist bench for a while now, but they can wreak havoc with sensitive circuits if you’re not careful. The problem: noise generated by the switch-mode supply buried within them. Is there anything you can do about the noise?

As it turns out, yes there is, and [Shahriar] at The Signal Path walks us through a basic circuit to reduce noise from DC-DC converters. The module under the knife is a popular buck-boost converter with a wide input range, 0-32 VDC output at up to 5 amps, and a fancy controller with an LCD display. But putting the stock $32 supply on a scope reveals tons of harmonics across a 1 MHz band and overall ripple of about 66 mV. But a simple voltage follower built from a power op-amp and a Zener diode does a great job of reducing the spikes and halving the ripple. The circuit is just a prototype and is meant more as a proof of principle and launching point for further development, and as such it’s far from perfect. The main downside is the four-volt offset from the input voltage; there’s also a broad smear of noise at the high end of the spectrum that persists even with the circuit in place. Centered around 900 MHz as it is, we suspect a cell signal of some sort is getting in. 900 kHz.

If you haven’t checked out the videos at The Signal Path, you really should. [Shahriar] really has a knack for explaining advanced topics in RF engineering, and has a bench to die for. We’ve covered quite a few of his projects before, from salvaging a $2700 spectrum analyzer to multiplexing fiber optic transmissions.

Continue reading “Cleaning Up A Low-Cost Buck-Boost Supply” →

Hackaday Prize Entry: Scorpion DC-DC Voltage Converter

October 4, 2017 by 32 Comments

Finding the right wall wart or charger to go with an appliance might be a matter of convenience to you and I, but there are some people who really, really need the right charger, because not having it could mean a fire.

[marius] is a Romanian hardware engineer who moved to Papua New Guinea, where he had the opportunity to travel in the remote jungle of that country. There, he saw many people who used solar panels to charge car batteries for a 3W light bulb at night, their phones, or other conveniences that only need a few Watt-hours a day. Connecting car batteries directly to solar panels isn’t a smart idea, so [marius] set out to create a simple, very low-cost DC-DC voltage converter. He’s calling it the Scorpion 3.0, and it looks like a fantastic tool for low-income areas that are far off the grid.

The design of the Scorpion consists of a 3D printed enclosure, with one forked end containing some alligator clip leads, and a standard barrel jack on the other. In the middle is a character display showing the input and output voltage, and a simple rotary encoder for user interaction. The circuit for the Scorpion 3.0 consists mostly of a cheap, low-power MSP430 microcontroller managing the display, encoder, and a buck converter.

Designing something for off-the-grid usage means a few engineering challenges, and being in Paupa New Guinea, there are a few environmental considerations as well. [marius] is varnishing his 3D prints. No, it’s not going to be IP68 rated, but it helps. Making the Scorpion cheap is also a big consideration, most probably resulting in the choice of the MSP430.

It’s a great project, and an excellent entry to the Hackaday Prize. You can check out the demo video of the Scorpion below.

Continue reading “Hackaday Prize Entry: Scorpion DC-DC Voltage Converter” →

LiPo Added To LEGO Power Functions Power Brick

September 10, 2017 by 12 Comments

LEGO’s Power Functions elements mostly consist of DC motors and the hardware to be driven by those motors like gears and wheels. They also include battery packs, usually a bunch of AA cells in a plastic box. One of the challenges of the system — for hackers, anyway — is interfacing with the product line’s plugs, which resemble 2×2 plates with power and ground connectors built in, designed to be impossible to connect in reverse. It’s difficult to make the physical shape of the plug, with the connectors right where they should be. This hurdle means you also pretty much have to use LEGO’s power boxes or take your chances with frying your components from an unregulated LiPo.

The LiPo Power Brick project serves as a DC-DC power supply, serving up constant 9 V output, with
over current protection limiting current to 3 A peak or 2 A continuous and over-discharge protection shutting down the power supply when it zeroes out. It can be used in conjunction with Sbrick smart Power Functions controllers. The SBrick can also source 3A per channel, which is more than any LEGO PF-compatible power supply can deliver.

The LiPo Power Brick is the same size as a standard 2×4 brick, allowing you to easily add it to your next project.

Killer USB Drive Is Designed To Fry Laptops

March 11, 2015 by 183 Comments

[Dark Purple] recently heard a story about how someone stole a flash drive from a passenger on the subway. The thief plugged the flash drive into his computer and discovered that instead of containing any valuable data, it completely fried his computer. The fake flash drive apparently contained circuitry designed to break whatever computer it was plugged into. Since the concept sounded pretty amazing, [Dark Purple] set out to make his own computer-frying USB drive.

While any electrical port on a computer is a great entry point for potentially hazardous signals, USB is pretty well protected. If you short power and ground together, the port simply shuts off. Pass through a few kV of static electricity and TVS diodes safely shunt the power. Feed in an RF signal and the inline filtering beads dissipate most of the energy.

To get around or break through these protections, [Dark Purple]’s design uses an inverting DC-DC converter. The converter takes power from the USB port to charge a capacitor bank up to -110VDC. After the caps are charged, the converter shuts down and a transistor shunts the capacitor voltage to the data pins of the port. Once the caps are discharged, the supply fires back up and the cycle repeats until the computer is fried (typically as long as bus voltage is present). The combination of high voltage and high current is enough to defeat the small TVS diodes on the bus lines and successfully fry some sensitive components—and often the CPU. USB is typically integrated with the CPU in most modern laptops, which makes this attack very effective.

Thanks for the tip, [Pinner].

A Primer On Buck (and Boost) Converters

January 24, 2015 by 13 Comments

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” →