Six Shooter Swaps Powder For Popped Capacitors

August 29, 2022 by Tom Nardi 43 Comments

Modern firearms might seem far removed from the revolvers of the Old West, but conceptually, they still operate on the same principle: exploding gunpowder. But as anyone who has put too much voltage through an electrolytic capacitor knows, gunpowder isn’t the only thing that explodes. (Yes, it isn’t technically an explosion.)

[Jay Bowles] wondered if it would be possible to construct an electrically-fired weapon that used used a standard capacitor in place of the primer and powder of a traditional cartridge. While it would naturally have only the fraction of the muzzle velocity or energy of even the smallest caliber firearm, it would be an interesting look at an alternate approach to what has been considered a largely solved problem since the mid-1800s.

In his latest Plasma Channel video, [Jay] walks viewers through the creation of his unconventional pistol, starting with a scientific determination of how much energy you can get out of popped capacitor. His test setup involved placing a capacitor and small projectile into an acrylic tube, and noting the relation between the speed of the projectile and the voltage passed through the cap. At 30 VDC the projectile would reliably fire from the barrel of his makeshift cannon, but by tripling the voltage to 90 VDC, he noted that the muzzle velocity saw the same 3X improvement.

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A Guide To 3D Printing Model Aircraft Wings

August 26, 2022 by Danie Conradie 32 Comments

The exact airfoil shape of a wing has a massive effect on the performance and efficiency of an aircraft and will be selected based on the intended flight envelope. If you’re moving beyond foam board wings, 3D printing is an excellent way to create an accurate airfoil, and [Tom Stanton] provides us with an excellent guide to modeling wing sections for easy printing.

[Tom] used the process demonstrated in the video after the break to create the wing for his latest VTOL RC aircraft. It was printed with lightweight PLA, which can ooze badly when it stops extruding. To get around this, he designed the wings and their internal ribs to be printed in one continuously extruded line.

He wanted a wing that would allow a smooth transition from hover to forward flight, and used the Airfoil Tools website to find and download the appropriate airfoil profile. After importing the profile into Fusion 360, he created internal ribs in a diagonal grid pattern, with lightening holes running along the length of the wing. A cylinder runs along the core of the wing to fit a carbon fiber wing spar. The ribs are first treated as a separate body in CAD and split into four quadrants. When these quadrants combine with the outer shell, it allows the slicer to treat the entire print as a continuous external perimeter line using “vase mode“.

These steps might seem simple, but it took about 3 weeks of experimentation to find a process that works. It’s primarily intended for straight wings with a continuous profile, but it should be adaptable to tapered/swept wings too. A well-designed airframe is essential when pushing aircraft to the edge of efficiency, like solar-powered plane to fly overnight.

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The Chip Shortage Leads To The Strangest Things

August 13, 2022 by Jenny List 19 Comments

The global chip shortage has not made the life of the electronic design engineer an easy one, as products have been designed around whatever parts are available rather than the first choices. This has manifested itself in some unexpected ways, including as [CNX software] investigates, products whose multiple-choice bill of materials has led to mistakes being made in manufacture.

On the face of it, designing a PCB with two sets of footprints to accommodate more than one part choice is a clever move. But as Radxa found out with their Rock 3A single board computer, this could lead to a production mishap as some boards left the production line with a mix-and-match BoM in their USB PD circuitry which left them unable to operate from voltages above 5 V. The board has footprints for both an Injoinic and a WCH part, and the faulty boards appear to have the support components fitted for the other chip to the one on the board.

We’d join [CNX] in congratulating Radxa for coming clean, and we like that one of the options to fix it is to be sent the chip to fit yourself. We’re left rather glad that it wasn’t us on whose watch such a mistake occurred, as from experience we know these things can happen all too easily.

Has the chip shortage led to any similar production mistakes in your life? Let us know in the comments.

Should’ve Used A 555 — Or 276 Of Them

August 10, 2022 by Dan Maloney 33 Comments

When asked to whip up a simple egg timer, most of us could probably come up with a quick design based on the ubiquitous 555 timer. Add a couple of passives around the little eight-pin DIP, put an LED on it to show when time runs out, and maybe even add a pot for variable timing intervals if we’re feeling fancy. Heck, many of us could do it from memory.

So why exactly did [Jesse Farrell] manage to do essentially the same thing using a whopping 276 555s? Easy — because why not? Originally started as an entry in the latest iteration of our 555 Contest, [Jesse]’s goal was simple — build a functional timer with a digital display using nothing but 555s and the necessary passives. He ended up needing a few transistors and diodes to pull it off, but that’s a minor concession when you consider how many chips he replaced with 555s, including counters, decoders, multiplexers, and display drivers. All these chips were built up from basic logic gates, a latch, and a flip-flop, all made from one or more 555s, or variants like the 556 or 558.

As one can imagine, 276 chips take a lot of real estate, and it took eleven PCBs to complete the timer. A main board acts as the timer’s control panel as well as serving as a motherboard for ten other cards, each devoted to a different block of functions. It’s all neat and tidy, and very well-executed, which is in keeping with the excellent documentation [Jesse] produced. The whole thing is wonderfully, needlessly complex, and we couldn’t be more tickled to feature it.

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Turning A Pair Of Syringes Into A Tiny Water Pump

July 31, 2022 by Danie Conradie 6 Comments

There is something inherently fascinating about tiny mechanical devices, especially when you’re used to seeing much larger versions. This is the case with [Penguin DIY]’s tiny centrifugal water pump built from 5 ml syringes.

The pump is powered by a small 8 mm diameter brushed DC motor, likely the same type that is used for small toy-grade quadcopters. The tiny impeller is a section of the syringe’s original plunger, with its cross-shaped body acting as the impeller blades. [Penguin DIY] first experimented with the original plunger seal to protect the motor from water, but it quickly melted from friction with the spinning shaft. Silicone sealant was used instead, and the motor shaft was covered with a layer of oil to prevent the sealant from sticking to it. Then the blob of sealant was flattened with a translucent plastic disc to allow clearance for the impeller.

A hole was drilled in the side of the syringe where the impeller sits, and a nozzle cut from the tip of another syringe was glued in place as the outlet. It’s notoriously difficult to get anything to stick to polypropylene syringes, but [Penguin DIY] says in the comments he was able to find an “organic superglue” that worked. With the motor and impeller inserted, the remaining space was also sealed with silicone.

This tiny pump packs a surprising amount of power, and was able to empty a 1.5 l bottle in about one minute with enough pressure to send the jet of water flying. There are still some issues that need to be addressed, though. With the motor completely sealed, it could burn itself quite quickly. A commenter also mentioned that it might suck water into the motor past the shaft after a hot run, as the air inside the motor cools and contracts. Even so, this little pump might be practical for applications that only require short runs, like watering potted plants. If you need more power you could always 3D print a larger pump.

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Fix Old Caps, But Keep That “Can Capacitor” Look

July 30, 2022 by Donald Papp 21 Comments

Vintage electronics and capacitor replacements tend to go hand-in-hand. Why? Because electrolytic capacitors just don’t last, not the way most other components do, anyway.

The metal terminal ring and the central plate are kept for re-use, and the metal case re-crimped after the internals of the capacitor are replaced with a modern equivalent.

It’s one thing to swap old caps with modern replacements, but what about electronics where the components are not hidden away, and are an important part of the equipment’s look? [lens42] shares a method for replacing antique can-style capacitors in a way that leaves them looking completely original. All it takes is some careful application of technique.

The first thing to do is carefully file away the crimp of the metal can until one can release the ring and plate that hold the terminals. Once that is off, the internals can be pulled from the metal can for disposal. Since the insides of the old cap won’t be re-used, [lens42] recommends simply drilling a hole, screwing in a lag bolt to use as a handle, and pulling everything out. There’s now plenty of space inside the old can to hold modern replacements for the capacitor, and one can even re-use the original terminals.

That leaves the job of re-crimping the old can around the terminal ring to restore a factory-made appearance. To best do this, [lens42] created a tapered collar. Gently hammering the can forces the bottom into the taper, and the opening gradually crimps around the terminal ring. It’s also possible to carefully hammer the flange directly, but the finish won’t be as nice. This new crimp job may not look exactly the same as before, but once the cap is re-installed into the original equipment, it won’t be possible to tell it has been modified in any way.

If this sounds a bit intimidating, don’t worry. [lens42] provides plenty of pictures. And if this kind of thing is up your alley, you may want to check out the Caps Wiki, an effort to centralize and share details about tech repair, especially for vintage electronics.

A New Way To Produce PCBs With Your 3D Printer

July 26, 2022 by Tom Nardi 49 Comments

With the low-cost PCB fabrication services available to hackers and makers these days, we’ll admit that making your own boards at home doesn’t hold quite the appeal that it did in the past. But even if getting your boards professionally made is cheaper and easier than it ever has been before, at-home production still can’t be beat when you absolutely must have a usable board before the end of the day.

If you find yourself in such a situation, this new method of DIY PCB production detailed by [Adalbert] might be just what you need. This unique approach uses a desktop fused deposition modeling (FDM) 3D printer throughout all of its phases, from creating a stencil based on the exported board design, to warming the UV soldermask to accelerate the curing process. It may not be an ideal choice for densely packed boards with fine-pitch components, but could definitely see it being useful for many prototypes.

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