power supply

182 Articles

AC-DC Converter Is Reliable, Safe, And Efficient

July 12, 2023 by 25 Comments

When first starting an electronics project, it’s not uncommon to dive right in to getting the core parts of the project working. Breadboarding the project usually involves working with a benchtop power supply of some sort, but when it comes to finalizing the project the actual power supply is often glossed over. It’s not a glamorous part of a project or the part most of us want to be working with, but it’s critical to making sure projects don’t turn up with mysterious issues in the future. We can look to some others’ work to simplify this part of our projects, though, like this power supply from [hesam.moshiri].

The power supply is designed around a switch-mode topology known as a flyback converter. Flyback converters work by storing electrical energy in the magnetic field of a transformer when it is switched on, and then delivering that energy to the circuit when it is switched off. By manipulating the switching frequency and turns ratios of the transformer, the circuit can have an arbitrary output voltage. In this case, it is designed to take 220V AC and convert it to 8V DC. It uses a simplified controller chip to decrease complexity and parts count, maintains galvanic isolation for safety, and is built to be as stable as possible within its 24W power limitation to eliminate any potential issues downstream.

For anyone trying to track down electrical gremlins in a project, it’s not a bad idea to take a long look at the power supply first. Any noise or unwanted behavior here is likely to cause effects especially in projects involving sensors, ADC or DAC, or other low-voltage or sensitive components. The schematic and bill of materials are available for this one as well, so anyone’s next project could use this and even make slight adjustments to change the output voltage if needed. And, if this is your first introduction to switched-mode power supplies, check out this in-depth look at the similar buck converter circuit to better understand what’s going on behind the scenes on these devices.

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Tearing Down And Improving A Professional Power Supply

July 11, 2023 by 11 Comments

[OZ2CPU] has an HP power supply that is about 30 years old. It looks brand new, though, and has three outputs and includes tracking for the adjustable positive and negative supply. After a quick demo of the unit’s features, he tears it all down so we can see inside. You can catch the video below.

Some similar supplies offer a 10-turn adjustment knob, but this one doesn’t. Inside is a beefy transformer and quite a few through-hole components. There was room to change the main adjusted pot to a 10-turn unit, so he made the mod.

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High Voltage Power Supply From USB

April 30, 2023 by 14 Comments

Those who work in different spaces may have different definitions of the term “high voltage”. For someone working on the GPIO pins of a Raspberry Pi it might be as little as 5 volts, someone working on a Tesla coil might consider that to be around 20 kV, and an electrical line worker might not reference something as HV until 115 kV. What we could perhaps all agree on, though, is that getting 300 volts out of a USB power supply is certainly a “high voltage” we wouldn’t normally expect to see in that kind of context, but [Aylo6061] needed just such a power supply and was eventually able to create one.

In this case, the high voltages will eventually be used for electrophoresis or electrowetting. But before getting there, [Aylo6061] has built one of the safest looking circuits we’ve seen in recent memory. Every high voltage part is hidden behind double insulation, and there is complete isolation between the high and low voltage sides thanks to a flyback converter. This has the benefit of a floating ground which reduces the risk of accidental shock. This does cause some challenges though, as voltage sensing on the high side is difficult while maintaining isolation, so some clever tricks were implemented to maintain the correct target output voltage.

The control circuitry is based around an RP2040 chip and is impressive in its own right, with USB isolation for the data lines as well. Additionally the project code can be found at its GitHub page. Thanks to a part shortage, [Aylo6061] dedicated an entire core of the microprocessor to decoding digital data from the high voltage sensor circuitry. For something with a little less refinement, less safety, and a much higher voltage output, though, take a look at this power supply which tops its output voltage around 30 kV.

LED Driver Circuit For Safety Hat Sucks Single AAA Cell Dry

January 19, 2023 by 21 Comments

[Petteri Aimonen] created an omnidirectional LED safety light to cling to his child’s winter hat in an effort to increase visibility during the dark winter months, but the design is also great example of how to use the Microchip MCP1640 — a regulated DC-DC step-up power supply that can run the LEDs off a single AAA cell. The chip also provides a few neat tricks, like single-button on/off functionality that fully disconnects the load, consuming only 1 µA in standby.

[Petteri]’s design delivers 3 mA to each of eight surface-mount LEDs (which he says is actually a bit too bright) for a total of about 20 hours from one alkaline AAA cell. The single-layer PCB is encased in a clear acrylic and polycarbonate enclosure to resist moisture. A transistor and a few passives allow a SPST switch to act as an on/off switch: a short press turns the unit on, and a long press of about a second turns it back off.

One side effect is that the “off” functionality will no longer work once the AAA cell drained too badly, but [Petteri] optimistically points out that this could be considered a feature: when the unit can no longer be turned off, it’s time to replace the battery!

The usual way to suck a battery dry is to use a Joule Thief, and while this design also lights LEDs, it offers more features and could be adapted for other uses easily. Interested? [Petteri] offers the schematic, KiCAD file for the PCB, and SVG drawing of the enclosure for download near the bottom of the project page.

A Very Tidy ATX Bench PSU

December 8, 2022 by 20 Comments

If there’s one thing that for decades of desktop PCs have given us, it’s a seemingly endless supply of relatively capable power supplies. If you need 5 volts or 12 volts at a respectable current they’re extremely useful, so quite a few people have used them as bench power supplies. Some of these builds box up the mess of wires into a set of more useful connectors, but [Joao Pinheiro] has taken his to the next level with a very neat 3D printed case and a set of variable switching regulators to make a variable bench supply with a top voltage of 60 volts.

In many ways it’s a straightforward wiring job to build, but there’s an unexpected power resistor involved. It’s sinking the 5 volt line, and we’re guessing that some current is required here for the PC power supply to run reliably. The thought of a high power resistor dumping heat into a 3D printed case leads us to expect that things might become a little melty though.

ATX power supplies are so numerous as to be expendable, so it’s always worth regarding them as a source of parts as well as a power supply.

Simple ATX Bench Power Supply Adds Variable Output

December 1, 2022 by 24 Comments

A benchtop power supply is a key thing to have for any aspiring electronics hacker. While you can always buy one, plenty of us have old computer PSUs lying around that could do a fine job themselves. [Frugha] decided to whip up a neat 3D-printed design for converting any ATX PSU into a usable bench unit.

The design features banana plugs outputting +12V, -12V, +5V, and +3.3V, with all outputs appropriately fused for safety. There’s also a fused stepdown converter used to supply variable voltages as needed. Its original trimpot was replaced with a multi-turn pot for ease of control. To make everything work, a load resistor on the 5V circuit makes the power supply think it’s hooked up to a motherboard. It’s all wrapped up in a neat slant-sided 3D-printed case that fits onto the ATX power supply itself.

The result is a neat and tidy power supply built out of readily-available components. We particularly like the addition of the stepdown converter – most ATX-based projects don’t offer variable output, which can nonetheless come in handy.

We’ve seen some other great builds along these lines before, too. If you’ve been cooking up your own homebrew power supply, don’t hesitate to share it on the tipsline! 

Rescue That Dead Xbox With An External PSU

December 1, 2022 by 13 Comments

There is nothing worse than that sinking feeling as a computer or other device fails just after its warranty has expired. [Robotanv] had it with his Xbox Series S whose power supply failed, and was faced with either an online sourced PSU of uncertain provenance, or a hefty bill from Microsoft for a repair. He chose to do neither, opening up his console and replacing the broken PSU with a generic external model. See the video below the break.

The Xbox appears surprisingly well designed as a modular unit, so accessing and unplugging its PSU was quite easy. To his surprise he found that the connections were simply two wires, positive and negative lines for 12 V. The solution was to find a suitably beefy 12 V supply and wire it up, before continuing gaming.

Beyond that simple description lies a bit more. The original was a 160 W unit so he’s taken a gamble with a 120 W external brick. He’s monitoring its temperature carefully to make sure, but with his gaming it has not been a problem. Then there’s the board wiring, which he appears to have soldered to pads on the PCB. We might have tried to find something that fit the original spade connectors instead, but yet again it hasn’t caused him any problems. We’d be curious to see what has failed in the original PSU. Meanwhile we’re glad to see this Xbox ride again, it’s more than can be said for one belonging to a Hackaday colleague.

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