Lessons Learned From A High-Voltage Power Supply

January 18, 2024 by Dan Maloney 8 Comments

When you set out to build a 60,000-volt power supply and find out that it “only” delivers a measly 50,000 volts, you naturally have to dive in and see where things can be improved. And boy, did [Advanced Tinkering] find some things to improve.

First things first: if you haven’t seen [Advanced]’s first pass at a high-voltage supply, you should go check that out. We really liked the design of that one, and were particularly impressed with the attention to detail, all of which seemed to be wisely geared to the safe operation of the supply. But as it turns out, the margin of safety in the original design wasn’t as good as it could be. Of most concern was the need to physically touch the supply to control it, an obvious problem should something go wrong anywhere along the HV path, which includes a ZVS-driven flyback and an epoxy-potted Crockcroft-Walton voltage multiplier.

To make things a little more hands-off, [AT] added a pneumatically actuated switch to the supply, along with some indicator lights to help prevent him from leaving the supply powered up. He also reworked the low-voltage DC supply section, replacing a fixed-voltage supply and a DC-DC converter with a variable DC supply. This had the side benefit of providing a little bit more voltage to the ZVS driver, which goosed up the HV output a bit. The biggest change, though, was to the potted part of the HV section, which showed signs of arcing to the chassis. It turns out that even at 100% infill, 3D printed PLA isn’t a great choice for HV projects; more epoxy was the answer to that problem. Along with rewinding the primary on the flyback transformer, the power supply not only hit the 60-kV spec, but even went a little past that — and all without any of that pesky arcing.

We thought [Advanced Tinkering]’s first pass on this build was pretty slick, but we’re glad to see that it’s even better now. And we’re still keen to see how this supply will be put to use; honestly, the brief teaser at the end of the video wasn’t much help in guessing what it could be.

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Low-Tech Fix Saves Expensive, High-Tech TV From Junk Pile

October 27, 2020 by Donald Papp 67 Comments

Wiggling this connector caused the backlight to turn off and on.

[Tweepy]’s TV stopped working, and the experience is a brief reminder that if a modern appliance fails, it is worth taking a look inside because the failure might be something simple. In this case, the dead TV was actually a dead LED backlight, and the fix was so embarrassingly simple that [Tweepy] is tempted to chalk it up to negligently poor DFM (design for manufacture) at best, or even some kind of effort at planned obsolescence at worst.

What happened is this: the TV appeared to stop working, but one could still make out screen content while shining a bright light on the screen. Seeing this, [Tweepy] deduced that the backlight had failed, and opened up the device to see if it could be repaired. However, the reason for the backlight failure was a surprise. It was not the power supply, nor even any of the LEDs themselves; the whole backlight wouldn’t turn on because of a cheap little PCB-to-PCB connector, and the two small spring contacts inside that had failed.

The failed connector, once cut open, showed contacts in poor condition (click to enlarge). It was ditched for a soldered connection, and the TV lived again.

From the outside things looked okay, but wiggling the connector made the backlight turn on and off, so the connection was clearly bad. Investigating further, [Tweepy] saw that the contact points of the PCBs and the two little conductors inside the connector showed clear signs of arcing and oxidation, leading to a poor connection that eventually failed, resulting in a useless TV. The fix wasn’t to clean the contacts; the correct fix was to replace the connector with a soldered connection.

Using that cheap little connector doubtlessly saved some assembly time at the factory, but it also led to failure within a fairly short amount of time. Had [Tweepy] not been handy with a screwdriver (or not bothered to investigate) the otherwise working TV would doubtlessly have ended up in a landfill.

It serves as a good reminder to make some time to investigate failures of appliances, even if one’s repair skills are limited, because the problem might be a simple one. Planned obsolescence is a tempting doorstep upon which to dump failures like this, but a good case can be made that planned obsolescence isn’t really a thing, even if manufacturers compromising products in one way or another certainly is.

Do Space Probes Fail Because Of Space Weather?

September 11, 2018 by Brian Benchoff 40 Comments

Over the past few decades, numerous space probes sent to the far-flung reaches of the Solar System have fallen silent. These failures weren’t due to communications problems, probes flying into scientifically implausible anomalies, or little green men snatching up the robotic scouts we’ve sent out into the Solar System. No, these space probes have failed simply because engineers on Earth can’t point them. If you lose attitude control, you lose the ability to point a transmitter at Earth. If you’re managing a space telescope, losing the ability to point a spacecraft turns a valuable piece of scientific equipment into a worthless, spinning pile of junk.

The reasons for these failures is difficult to pin down, but now a few people have an idea. Failures of the Kepler, Dawn, Hayabusa, and FUSE space probes were due to failures of the reaction wheels in the spacecraft. These failures, in turn, were caused by space weather. Specifically, coronal mass ejections from the Sun. How did this research come about, and what does it mean for future missions to deep space?

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Perf Board Pyrotechnics Courtesy Of A High-Voltage Supply

August 26, 2018 by Dan Maloney 21 Comments

You may have asked yourself at one time or another, “Self, what happens when you pass 100 thousand volts through a printed circuit board?” It’s a good question, and [styropyro] put together this fascinating bit of destructive testing to find out.

Luckily, [styropyro] is well-positioned to explore the high-voltage realm. His YouTube stock-in-trade is lasers, ranging from a ridiculously overpowered diode-laser bazooka to a bottle-busting ruby laser. The latter requires high voltage, of course, and his Frankenstein’s lab yielded the necessary components for this destructive diversion. A chopper drives dual automotive ignition coils to step the voltage up to a respectable 100 kV. The arcs across an air gap are impressive enough, but when applied to a big piece of copper-clad protoboard, the light show is amazing. The arcs take a seemingly different path across the board for each discharge, lighting up the path with an eerie blue glow accompanied by a menacing buzz. Each discharge path may be random, but they all are composed of long stretches across the rows and columns of copper pads that never take the more direct diagonal path. [styropyro]’s explanation of the math governing this behavior is feasible, but really we just liked looking at the pretty and dangerous display. Now if only the board had been populated with components…

No, there’s not much of a hack here, but it’s cool nonetheless. And it’s probably a well-earned distraction from his more serious stuff, like his recent thorough debunking of the “Chinese laser rifle” that was all over the news a while back.

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A Dramatic Demo Of AC Versus DC Switching

July 24, 2018 by Dan Maloney 48 Comments

Switches seem to be the simplest of electrical components – just two pieces of metal that can be positioned to either touch each other or not. As such it would seem that it shouldn’t matter whether a switch is used for AC or DC. While that’s an easy and understandable assumption, it can also be a dangerous one, as this demo of AC and DC switching dramatically reveals.

Using a very simple test setup, consisting of an electric heater for a load, a variac to control the voltage, and a homemade switch, [John Ward] walks us through the details of what happens when those contacts get together. With low-voltage AC, the switch contacts exhibit very little arcing, and even with the voltage cranked up all the way, little more than a brief spark can be seen on either make or break. Then [John] built a simple DC supply with a big rectifier and a couple of capacitors to smooth things out and went through the same tests. Even at a low DC voltage, the arc across the switch contacts was dramatic, particularly upon break. With the voltage cranked up to the full 240-volts of the UK mains, [John]’s switch was essentially a miniature arc welder, with predictable results as the plastic holding the contacts melted. Don your welding helmet and check out the video below.

As dramatic as the demo is, it doesn’t mean we won’t ever be seeing DC in the home. It just means that a little extra engineering is needed to make sure that all the components are up to snuff.

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11,000 Volt Jacob’s Ladder Sounds Like A Lightsaber

March 5, 2015 by Rick Osgood 35 Comments

In the high-voltage world, a Jacob’s ladder is truly a sight to behold. They are often associated with mad scientist labs, due to both the awesome visual display and the sound that they make. A Jacob’s ladder is typically very simple. You need a high voltage electricity source and two bare wires. The wires are placed next to each other, almost in parallel. They form a slight “V” shape and are placed vertically. The system acts essentially as a short-circuit. The voltage is high enough to break through the air at the point where the wires are nearest to each other. The air rises as it heats up, moving the current path along with it. The result is the arc slowly raising upwards, extending in length. The sound also lowers in frequency as the arc gets longer, and once [Gristc] tuned his system just right the sound reminds us of the Holy Trilogy.

We’ve seen these made in the past with other types of transformers that typically put out around 15,000 Volts at 30mA. In this case, [Gristc] supersized the design using a much beefier transformer that puts out 11,000 Volts at 300mA. He runs the output from the transformer through eight microwave oven capacitors as a ballast. He says that without this, the system will immediately trip the circuit breakers in his house.

In the demo video below, you can see just how large the arc is. It appears to get about 10 inches long before breaking with a sound different from any Jacob’s ladders we’ve seen in the past as well. Continue reading “11,000 Volt Jacob’s Ladder Sounds Like A Lightsaber” →