Easy Power Supply Mod Takes Control

Inexpensive bench top power supplies are great for the home hobbyist, featuring wide voltage range and current limiting for a low price. What’s not to love? The controls; most have a single-turn pot that is typically very fidgety, especially at low voltage.

The solution is to replace the factory pots with nice wire-wound 10 turn units in order to gain 10x the precision. Of course nothing is ever drop in, the new pots didn’t fit the old holes, but that is nothing a few moments with a drill can’t fix. Also the original knobs no longer fit, but that’s just an opportunity for a knob upgrade.

The end result is still a power supply with fidgety controls, but instead of holding your breath, tippy tapping knobs to get within 100mV of your target, you can dial right in to within 10mV of your target. That makes life much easier, especially on low voltage projects that may not have power regulation quite yet.

Join us after the break for a video with all the info.

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Looking Inside the Arksen Dual Power Supply

I recently picked up an Arksen dual power supply. You’ve seen these before, I’m sure, under a variety of names in places ranging from electronics stores to eBay. They look amazing for the price, and while I didn’t expect it to measure up to some of the pro supplies I have, I just wanted something to stick under my desk instead of having to move things to the bench or–worse–drag a heavy power supply over to my desk.

When I was putting together the sonic motion sensor, I found that the HC-SR04 module needed more current than I could draw out of an Arduino Leonardo. I figured this would be a good chance to use the new supply in anger. It seemed to work without too many problems. But there were a few things you might want to know if you have a similar supply or are thinking about getting a similar one.

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Programmable DC Backup Power Supply

The uninterruptible power supply was once a standard fixture in the small office/home office as a hedge against losing work when the electrons stop flowing from your AC outlet. Somewhat in decline as computing hardware shifts away from dedicated PCs toward tablets, phones and laptops, the UPS still has a lot of SOHO utility, and off-the-shelf AC units are easy to find. But if your needs run more to keeping the electrons flowing in one direction, then you might want to look at [Kedar Nimbalkar]’s programmable DC backup power system.

Built inside a recycled ATX power supply case, [Kedar]’s project is heavy on off-the-shelf components, like a laptop power supply for juice, a buck converter to charge the 12 volt sealed lead acid battery, and a boost converter to raise the output to 19.6 volts. An Arduino and an optoisolator are in charge of controlling the charging cycle and switching the UPS from charging the battery to using it when mains voltage drops.

 If you need a DC UPS but would rather skip the battery, you could try running a Raspberry Pi with electrons stashed in a supercapacitor. Or if you’ve got an aging AC UPS, why not try beefing it up with marine batteries?

[Thanks for the tip, Morris]

Retro TO-3 Switching Voltage Regulator

Restoring old gear often means replacing unavailable parts with modern equivalents. [Alex Eisenhut] needed to replace some old TO-3 voltage regulators and decided to make an authentic-looking switching power supply replacement. These three pin metal cans were very common, especially the LM340 5V regulator which was, of course, a linear regulator. Today, you are more likely to see a 7805 in a TO-220 case or something surface mount for a comparable linear regulator.

As you might expect, the board uses surface mount components. [Alex] used Mill Max machine pins to match the original regulator footprint and calls the regulator Ton3y. He plans to cover it up with a 3D printed lid, but it seems a shame to hide the fine PCB work.

In the pictures, you can see that the machine pins are a tight fit. [Alex] used a hammer to lightly tap them into place. Of course, the original TO-3 regulators were linear and would generate a lot of heat. The Ton3y, as you’d expect from a switching power supply, runs cool (according to the scientific measurement made with [Alex]’s pinky finger) and surely has a wider input voltage range and more output current capacity.

We’ve seen replacement switching regulators before, but this one is really a work of art.

Hackaday Prize Entry: A Better Bench Power Supply

Back in February, [The Big One] started building the bench power supply to rule them all. His previous power supply was just an ATX computer power supply. It worked, but that didn’t give him fancy stuff like different channels of individually adjustable voltages. Since then, we’ve spun up the 2015 Hackaday Prize, and [The Big One] has changed his DIY power supply into a Hackaday Prize entry that competes well against $1000 mid-range commercial units.

The single most expensive component in this power supply are a pair of isolated switched power supplies rated for 15V and 7A. This is a change from [The Big One]’s original plan to use a big ‘ol transformer; a switched mode supply is smaller, lighter, costs about the same, and is much better suited to the modular nature of the project.

The final design for this power supply has some interesting features: up to six channels are possible, voltage and current can go all the way down to zero, and everything can be controlled over USB. Those are amazing features that won’t be found in any $100 cheapo bench power supply, and [The Big One]’s amazing documentation for this project makes it a perfect entry for The Hackaday Prize.

The 2015 Hackaday Prize is sponsored by:

Making Your Own Laser Cut PSU

[Csaba] and his friend bought a 600W switching lab-style power supply unit off eBay a while ago, and after about a year of tangled wires and mess, finally decided to enclose it in a fancy box.

The PSU itself required some modification as it was just a controller and a power board — so they added a dedicated mains transformer, and a buffer capacitor. The housing is made out of 3mm plywood which they designed and laser cut specifically for the PSU — and it looks fantastic.

It includes a cooling fan, a small digital display and a whole bunch of controls for finely tuning your electronics power requirement — take a look at the demonstration video after the break.

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How To Reverse Engineer A PCB

For [Peter]’s entry for the 2015 Hackaday Prize, he’s attempting to improve the standard industrial process to fix atmospheric nitrogen. Why? Fertilizers. He’s come up with an interesting technique that uses acoustic transducers in a pressure vessel, and to power that transducer, he’s turned to the greatest scrap heap in the world: eBay. He found a cheap ultrasonic power supply, but didn’t know offhand if it would work with his experiments. That’s alright; it’s a great opportunity to demo some basic reverse engineering skills.

A few months ago, [Dave Jones] posted a great video where he reverse engineers the front end of the new Rigol Zed. The basic technique is to make a photocopy, get some transparency sheets, grab a meter, and go to town. [Peter]’s technique is similar, only he’s using digital image manipulation, Photoshop, and a meter.

The process begins by taking pictures of both sides of the board, resizing them, flipping one side, and making an image with several layers. The traces on the bottom of the board were flooded and filled with the paint bucket tool, and components and traces carefully annotated.

With some effort, [Peter] was able to create a schematic of his board. He doesn’t know if this power supply will work with his experiments; there’s still some question of what some components actually do. Still, it’s a good effort, a great learning opportunity, and another log in [Peter]’s entry to The Hackaday Prize