Using Metal Screws In Plastic Parts

April 10, 2026 by Al Williams 11 Comments

Machine screws aren’t made for wood or sheet metal, they make specific screws for those applications. You probably also know there are special screws for plastic. But did you know there are at least two distinct types? In a recent video, [Lost in Tech] show us different types of plastic screws, including thermal camera shots of screws driving into 3D printed parts, along with tests using a torque driver.

We have often used “any old” screw in printed parts, which usually works OK. We’ve also used threaded inserts or captive nuts, classic choices. One of the issues with screws or inserts is that you have to get accurately sized holes in your 3D prints.

In addition to learning about the types of screws and how best to accommodate them, he also developed a free web-based tool that does all the math for you.

Of course, there are cases when you do need a threaded insert. In particular, the plastic screws will tend to wear the plastic each time you insert them. If you expect the screw to go in and out many times, this might not be the right technique for you. On the other hand, if you think you might remove and replace the screws a few dozen times over the life of the part, this might be attractive.

We’ve covered self-tapping screws in plastic before, but, as the video shows, not all of them are created equal. And, of course, there are always heat-set inserts.

Continue reading “Using Metal Screws In Plastic Parts” →

Espressif’s New ESP32-S31: Dual-Core RISC-V With WiFi 6 And GBit Ethernet

April 8, 2026 by Maya Posch 40 Comments

In a move that’s no doubt going to upset and confuse many, Espressif has released its newest microcontroller — the ESP32-S31. The confusing part here is that the ESP32-S series was always the one based on Tensilica Xtensa LX7 cores, while the ESP32-C series was the one using RISC-V cores.

That said, if one looks at it as a beefier -S3 MCU it does have some appealing upgrades. The most obvious improvements are with the use of WiFi 6, as well as Bluetooth Classic and LE 5.4, including LE Audio. There is also Thread and Zigbee support for those who are into such things.

The Ethernet MAC got a bump from the 100 Mbit RMII MAC in previous MCUs and is now gigabit-rated, while the number of GPIO is significantly higher at 60 instead of 45 on the -S3. On the RAM side, things are mostly the same, except for DDR PSRAM support, with octal SPI offering up to 250 MHz compared to 80 MHz on the -S3.

On the CPU side the up-to-320 MHz RISC-V cores are likely to be about as powerful as the 240 MHz LX7 cores in the -S3, based on the ESP32-C series performance in terms of IPC. Overall it does seem like a pretty nice MCU, it’s just confusing that it doesn’t use LX7 cores with the series it was put into. When this MCU will be available for sale doesn’t seem to be known yet, with only samples available to select customers.

Thermostat? Do It With A 555!

April 7, 2026 by Al Williams 19 Comments

It is a running gag around here that whenever a project posts, someone will inevitably point out that it could have been done with a 555 timer IC. [Stephen Woodward] went the opposite way and built a simple thermostat using the ubiquitous chip.

To be fair, this isn’t some sophisticated PID controller — it’s basically a bang-bang controller. Since the device has a comparator and the circuits use a thermistor, it seems like a clever but simple idea on the surface. However, there are some neat tricks. For example, if you tie the 555 threshold pin to Vdd, then the trigger pin acts as an inverting analog comparator. Another nice feature: the setpoint depends on a resistance ratio, so there is no need for a precise input voltage reference.

A simple circuit change can switch the circuit to power a heater or a cooler. The chip can handle a surprising amount of power, but for some applications, you may need some output drive circuitry. The simple circuit even has hysteresis, which you can set with a different resistor. Pretty impressive for a cheap chip, two resistors, a thermistor, and a battery.

We’ve seen a lot of strange 555 circuits in our contests. We even had a 555 Timer Contest.

Watch An Electro-Permanent Magnet In Action

April 1, 2026 by Donald Papp 12 Comments

Electro-permanent magnets (EPMs) are pretty nifty concepts, and if you aren’t familiar with them, they are permanent magnets with the ability to be electrically switched on or off. Unlike an electromagnet — which maintains a magnetic field only while power is applied — an EPM can remain “on” even when power is removed. Want to see one work? There’s a video embedded below that shows one off, but if you’d like to know how they work, we have you covered.

Inside are two types of magnet, one of which is permanent and the other being a semi-hard magnet paired with an electromagnetic coil. A semi-hard magnet’s flux can be changed by exposing it to a strong enough magnetic field, and that’s the key to making it work.

When both magnets work together, the EPM is “on” and acts like a permanent magnet. To turn the EPM off, the polarity of the semi-hard magnet is flipped with a short and powerful electromagnetic pulse, after which the two magnets oppose one another and more or less cancel each other out. So rather than generating a magnetic field, an EPM more accurately reconfigures it.

As intriguing as EPMs are, we haven’t really seen one properly in action until it was brought to our attention that [Dave Jones] of EEVblog tried one out last year. He received a Zubax FluxGrip EPM, which is intended for drone and robotic applications and can hold up to 25 kg. Watch [Dave] fire it up in the video (link is cued up to the 7:30 mark), it’s pretty interesting to see one of these actually work.

EPMs are not prohibitively expensive but they are not exactly cheap, either. But if a switchable magnet sounds up your alley and you can’t afford an EPM, consider an alternative “switchable” magnet design that works by momentarily canceling out a permanent magnet with a paired electromagnet. Unlike an EPM, it’s not a permanent switch but it would be enough to drop a payload.

Continue reading “Watch An Electro-Permanent Magnet In Action” →

A Novel 555 Circuit In 2026

April 1, 2026 by Jenny List 22 Comments

The humble NE555 has been around for over five decades now, and while during that time we’ve seen a succession of better and faster versions of the original, the circuits which surround it are pretty well known. There can’t be anything new in the world of 555s, can there? [Stephen Woodward] claims he’s made a novel 555 circuit, with his 1 MHz linear voltage to frequency converter. Since he’s been in love with the 555 since 1974, we’re inclined to trust him on this part.

It’s visibly the 555 astable oscillator we’re all familiar with, given the addition of a current source in place of the normal charging resistor. This makes for a much more linear sawtooth waveform, but it still doesn’t fix the linearity of the voltage to frequency curve. The novel bit comes in adding an extra resistor between the threshold and discharge pins, with a value calculated for a time constant with the capacitor to match the 555’s own switching delay. This provides the necessary compensation, and gives the circuit its linearity.

This is so brilliantly simple that it’s almost a shock that it’s new, but it’s also a great example of the old-school electronic engineer’s art. We can’t think of an immediate need for a 555 voltage to frequency converter on the Hackaday bench at the moment, but you can bet we’ll come back to this one if we do.

We had someone pushing a newer 555 variant to its limit, when we ran our component abuse challenge.

Making A Nichrome Wirewound Power Resistor

March 28, 2026 by Maya Posch 19 Comments

Although not really a cost-effective or a required skill unless you have some very specific needs not met by off-the-shelf power resistor options, making your own own wirewound power resistor is definitely educational, as well as a fascinating look at a common part that few people spare a thought on. Cue [TheElectronBench]’s video tutorial on how to make one of these components from scratch.

The resistance value is determined by the length of nichrome wire, which is an alloy of nickel and chromium (NiCr) with a resistivity of around 1.12 µΩ/m. It’s also extremely durable when heated, as it forms a protective outer layer of chromium oxide. This makes it suitable for very high power levels, but also requires the rest of the power resistor assembly to be able to take a similar punishment.

For the inner tube of this DIY power resistor a tube of alumina ceramic was used, around which the nichrome wire is wound. This resistor targets 15 Ohm at a maximum load of 50 Watt, this means a current of about 1.83 A is expected at 27.4 V. The used nichrome wire has a measured resistance of 10.4 Ohm, ergo 1.44 meter has to be cut and wound.

This entire assembly is then embedded in refractory cement (fireproof cement), as this will keep the wire in place, while also able to take the intense temperature cycling during operation. As a bonus this will prevent toasting the surrounding environment too much, never mind lighting things on fire as the nichrome wire heats up.

As explained in the video, this is hardly the only way to create such a power resistor, with multiple types of alternative alloys available, different cores to wind around and various options to embed the assembly. The demonstrated method is however one that should give solid results and be well within the capabilities and budget of a hobbyist.

An important point with nichrome is that you cannot really solder to it, so you’ll need something along the lines of a mechanical (crimping) connection. There are also different winding methods that can affect the inductance of the resistor, since this type of resistor is by its design also a coil. This is however not covered in the video as for most applications it’s not an issue.

Overall, this video tutorial would seem to be a solid introduction to nichrome power resistors, including coverage of many issues you may encounter along the way. Feel free to sound off in the comment section with your own experiences with power resistors, especially if you made them as well.

ESP32: When Is A P4 A P4, But Not The P4 You Thought It Was

March 21, 2026 by Jenny List 28 Comments

We’re used to electronic parts of the same type staying predictably the same, sometimes over many years. An early Z80 from the mid 1970s can be exchanged with one from the end of production a few years ago, for example. This week, we’ve had DMs from several readers who’ve found that this is not always the case, and the culprit is surprising. Espressif has released a new revision of their P4 application processor, and though it’s ostensibly the same, there are a couple of changes that have been catching people out.

The changes lie in both hardware and software, in that there’s a pin that’s changed from NC to a power rail, a few extra passives are needed, and firmware must be compiled separately for either revision. The problem is that they are being sold as the same device and appear in some places under the same SKU! This is leading to uncertainty as to which P4 revision is in stock at wholesalers. We’ve been told about boards designed for the old revision being assembled with the new one, a situation difficult to rework your way out of. Designers are also left uncertain as to which firmware build is needed for boards assembled in remote factories.

The ESP32-P4 is an impressive part for its price, and we’re sure that we’ll be seeing plenty of projects using this new revision over the coming years. We’re surprised that it doesn’t have a different enough part number and that the wholesalers have seemingly been caught napping by the change. We’re told that some of the well-known Chinese assembly houses are now carrying the two chips as separate SKUs, but that’s scant consolation for a designer with a pile of boards carrying the wrong part. If you’re working with the P4, watch out, make sure your board is designed for the latest revision, and ask your supplier to check which chips you’ll get.

If the P4 is new to you, we’ve already seen a few projects using it.