How Good (Or Bad) Are Fake Power Semiconductors?

June 14, 2024 by Jenny List 12 Comments

We all know that there’s a significant risk of receiving fake hardware when buying parts from less reputable sources. These counterfeit parts are usually a much cheaper component relabeled as a more expensive one, with a consequent reduction in performance. It goes without saying that the fake is lower quality then, but by just how much? [Denki Otaku] has a video comparing two power FETs, a real and a fake one, and it makes for an interesting watch.

For once the fact that a video is sponsored is a positive, for instead of a spiel about a dodgy VPN or a game involving tanks, he takes us into Keysight’s own lab to work with some high-end component characterization instruments we wouldn’t normally see. A curve tracer produces the equivalents of all those graphs from the data sheet, while a double pulse tester puts the two transistors through a punishing high-power dynamic characteristic examination. Then back in his own lab we see the devices compared in a typical circuit, a high-power buck converter. The most obvious differences between the two parts reveal something about their physical difference, as a lower parasitic capacitance and turn-on time with a higher on resistance for the fake is a pointer to it being a smaller part. Decapping the two side by side backs this up.

So it should be no surprise that a fake part has a much lower performance than the real one. In this case it’s a fully working transistor, but one that works very inefficiently at the higher currents which the real one is designed for. We can all be caught by fakes, even Hackaday scribes.

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Studying The Finer Points Of 3D Printed Gears

June 12, 2024 by Dave Rowntree 33 Comments

[How to Mechatronics] on YouTube endeavored to create a comprehensive guide comparing the various factors that affect the performance of 3D printed gears. Given the numerous variables involved, this is a challenging task, but it aims to shed light on the differences. The guide focuses on three types of gears: the spur gear with straight teeth parallel to the gear axis, the helical gear with teeth at an angle, and the herringbone gear, which combines two helical gear designs. Furthermore, the guide delves into how printing factors such as infill density impact strength, and it tests various materials, including PLA, carbon fiber PLA, ABS, PETG, ASA, and nylon, to determine the best options.

The spur gear is highly efficient due to the minimal contact path when the gears are engaged. However, the sudden contact mechanism, as the teeth engage, creates a high impulse load, which can negatively affect durability and increase noise. On the other hand, helical gears have a more gradual engagement, resulting in reduced noise and smoother operation. This leads to an increased load-carrying capacity, thus improving durability and lifespan.

It’s worth noting that multiple teeth are involved in power transmission, with the gradual engagement and disengagement of the tooth being spread out over more teeth than the spur design. The downside is that there is a significant sideways force due to the inclined angle of the teeth, which must be considered in the enclosing structure and may require an additional bearing surface to handle it. Herringbone gears solve this problem by using two helical gears thrusting in opposite directions, cancelling out the force.

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Comparing Those Ten Cent Microcontrollers

June 10, 2024 by Jenny List 64 Comments

If you follow the world of microcontrollers, then you’ll probably be familiar with the most recent crop of ten cent parts. They bring power and features previously the preserve of much more expensive chips into the super-budget arena, and they’re appearing in plenty of projects on these pages.

If you’re not familiar with them it can seem daunting to decide which one to use, so to help you [Zach of All Trades] is comparing two of the more common ones. The CH32V003 with a RISC-V core and the PY32F002 with an ARM Cortex M0+ core are both pretty similar on paper, but which should you use?

The video below gives a run-down of each part along with some demonstrations before making its conclusions. The ARM-based part isn’t as quick as the RISC-V one but has a slight edge on peripherals, while the support is where a potential winner emerges in the shape of the CH32. That should be the last word, but for that the PY32 has the distance advantage over its rival of ready availability.

So this look at two families of cheap microcontrollers reveals the pros and cons of each, but in reality it provides an introduction to two sets of powerful chips for pennies.

As we’ve observed before, there are more chips to be found in this market.

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Gas-Tight FDM 3D Printing Is Within Your Grasp

June 8, 2024 by Jenny List 65 Comments

The widespread availability of inexpensive 3D printers has brought about a revolution in what can be easily made at home. However these creations aren’t perfect, particularly when it comes to the adhesion between their layers. Aside from structural failures along the layer lines there is also the question of those joins being permeable, limiting the possibility for waterproof or gas proof prints. It’s something [German Engineer] has tackled in a new video, in which he’s looking at the design and preparation of small propane tanks.

A blurry image of a red 3d-printed part exploding — This is the frame at which the 3D printed tank explodes

The attraction of propane as a fuel is that it liquefies easily on compression, so a propane cylinder or tank will be an equilibrium of liquid propane with pressurized gas above it, whose pressure depends on the ambient temperature. This means that any tank must be expected to have a working pressure somewhere between 150 and 200 PSI, with of course a design pressure far exceeding that for safety reasons.

Filling a 3D printed tank immediately results in the propane escaping, as he demonstrates by putting one of his prints under water. He solves this with a sealant, Diamant Dichtol, which is intended to polymerize in the gaps between layers and create a gas-tight tank. A range of three tanks of different thicknesses are treated this way, and while the 1 mm thick variety bursts, the thicker ones survive.

It’s clear that this technique successfully creates gas-tight prints, and we can see the attraction of a small and lightweight fuel tank. But we can’t help worrying slightly about the safety, for even when the material is a lightweight 3D print, high pressure equipment is not to be trifled with. Tanks do burst, and when that happens anyone unfortunate enough to be close by sustains nasty, even life-threatening injuries. Use the technique, but maybe don’t hit it with high pressures.

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Is That A Triboelectric Generator In Your Shoe?

June 6, 2024 by Elliot Williams 20 Comments

The triboelectric effect is familiar to anyone who has rubbed wool on a PVC pipe, or a balloon on a childs’ hair and then stuck it on the wall. Rubbing transfers some electrons from one material to the other, and they become oppositely charged. We usually think of this as “static” electricity because we don’t connect the two sides up with electrodes and wires. But what if you did? You’d have a triboelectric generator.

In this video, [Cayrex] demonstrates just how easy making a triboelectric generator can be. He takes pieces of aluminum tape, sticks them to paper, and covers them in either Kapton or what looks like normal polypropylene packing tape. And that’s it. You just have to push the two sheets together and apart, transferring a few electrons with each cycle, and you’ve got a tiny generator.

As [Cayrex] demonstrates, you can get spikes in the 4 V – 6 V range with two credit-card sized electrodes and fairly vigorous poking. But bear in mind that current is in the microamps. Given that, we were suprised to see that he was actually able to blink an LED, even if super faintly. We’re not sure if this is a testament to the generator or the incredible efficiency of the LED, but we’re nonetheless impressed.

Since around 2012, research into triboelectric nanogenerators has heated up, as our devices use less and less power and the structures to harvest these tiny amounts of power get more and more sophisticated. One of the coolest such electron harvesters is 3D printable, but in terms of simplicity, it’s absolutely hard to beat some pieces of metal and plastic tape shoved into your shoe.

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Old Knobs With A Cast Of Thousands

June 5, 2024 by Al Williams 6 Comments

You have an old radio — in the case of [The Radio Mechanic], a Stromberg Carlson — and it needs new knobs. What do you do? You can’t very well pop down to the local store and find any knobs anymore. Even if you are lucky enough to be around an electronics store, they aren’t going to have knobs to do justice to an antique radio. You could 3D print them, of course, but there are a number of issues with transferring the old knob to a CAD file for printing. So [The Radio Mechanic] decided to cast them instead.

He printed some fixtures to help with the molding using two-part molding silicone. He mounted the knob on a shaft in a jig, filled the jig with silicone, and lowered the knob into the mix. The next day, he had a good-looking mold.

The next step, of course, is to cast with resin. Admittedly 3D printing would have been faster, but would not have as nice a surface finish. The epoxy resin is clear, but he was hopeful that some caramel pigment would match the original knob color. Spoiler alert: it didn’t. The resulting knob looked translucent, like a root beer barrel candy, rather than the brown sugar color of the original knob.

The knob needed a spring insert to hold the shaft, so he repurposed some from a different kind of radio. Overall, this is the kind of thing we always think we are going to do when we need something and then we rarely follow through. Then again, we rarely have the patience to wait as long as these two knobs took to make.

Of course, a casting guerrilla doesn’t have to make just knobs. You can even add metal powders to do cold metal casting.

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Make A Super Cute LiDAR Measurement Module

June 2, 2024 by Donald Papp 10 Comments

This ultra-cute tiny LiDAR rangefinder project by [gokux] can be thought of as a love letter to the incredible resources and components hobbyists and hackers of all types have access to nowadays. In fact, it all stemmed from coming across a miniscule half-inch 64×32 OLED display module that was simply too slick to pass up.

USB connector for charging on the bottom, hole for distance sensor out the top.

To use it, one simply powers it on and the display will read out the distance in millimeters. The VL53L0X time-of-flight sensor inside works by sending out a laser pulse and measuring how long it takes for the pulse to bounce back. We hope you’re curious about what such a sensor looks like on the inside, because here’s a nifty teardown of these fantastic devices. The device can technically measure distances of up to 2 m, but [gokux] says accuracy drops off after 1 m.

The main components besides the OLED display and VL53L0X sensor are an ESP32-C3 board (which handily integrates battery charging circuitry), 3D-printed enclosure, tiny rechargeable battery, and power switch. The whole thing is under one cubic inch. Not bad, and it even makes a passable keychain. Parts list, code, and 3D model files, including STEP format, are all available if you’d like to spend an afternoon making your own.