Investigating Whether Zener Diodes Work For ESD Protection

November 2, 2026 by 1 Comment

Sometimes the naming of parts in electronics can contribute to confusion about what they are good for, with the topic of Zener diodes in the context of fast surges like those from electrostatic discharge (ESD) being a good example. In a recent video by [BTT Lab] this particular question regarding Zener suitability for suppressing ESD is addressed, as compared to transient-voltage-suppression (TVS) diodes.

The main argument against using Zener diodes for ESD and similar surge suppression is that they react too slowly, which obviously gives said surge time to cause some real damage. This is where a special form of avalanche effect-based diodes called TVS diodes are recommended, as their response time is in the picoseconds rather than nanoseconds or slower as for Zener diodes.

Although this is technically true, as also pointed out in the video, a Zener diode also uses the avalanche effect, with the diode starting off conducting in the reverse direction using the Zener effect before transitioning to the much faster avalanche effect. The transition point is hereby determined by how heavily the p-n junction is doped, making effectively all Zener diodes also avalanche diodes.

TVS diodes consequently are basically Zener diodes that are optimized for a very early transition to said avalanche effect. They are also generally larger than typical Zener diodes as they generate a lot of internal thermal energy while in reverse conducting mode, which has to be contained and shed without causing permanent damage.

The short version is thus that diodes marked as ‘TVS’ are the best choice for surge protection, while those marked as ‘Zener’ are best used for voltage clamping, reference voltages and all other typical Zener diode things.

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Ask Hackaday: What Puts This Photo In The Pink?

November 2, 2026 by 5 Comments

It’s an exciting time to be a camera hacker, because we are at a moment when even cheap camera hardware is starting to have high resolution sensors, and the awesome camera phones of a few years ago are now in people’s junkboxes. Lens swapping has been a feature of the art for a while now, usually taking the form of a C-mount add-on. So with a bit of 3D printing and glue, you can now make something more interesting from an AliExpress purchase or that old phone. These cameras have all the resolution and sharpness that the sensor can deliver assuming that their software isn’t too awful, but there’s a persistent problem . The photographs invariably have a pinkish tint, as reported in a recent Hackaday-featured project, just to name one. The original lens doesn’t have this problem, so what’s up?

A mobile phone with a C-mount lens attached to its back, propped up on a laptop keyboard with the screen towards us. The screen shows a blurry view of the laptop.
Without the pink stuff, it’s not a bad camera, really.

Of course, the more astute readers are immediately thinking about IR filters. I did too, when one of my on-and-off projects had the pink tint. It’s a Samsung Galaxy Tab 3, an ancient Android 5 phone with a rather useless and gimmicky stylus, and a rather nice camera sensor. I bought a replacement camera module for it on AliExpress so I’d have something to experiment with, removed its lens assembly, and had a phone with a bare sensor peeking from the back of it. A 3D printed adjustable lens mount assembly that I’ll eventually clean up and release so any phone can have the same modification followed.

Faced with the dreaded pink when I started taking pictures, I ineptly glued an IR filter to the back of it, and awaited my perfect shots. Sadly they never came, so rather than admit defeat, I’m hoping one of you lot can help. Are any Hackaday readers in the optics business and can tell me what’s up? Continue reading “Ask Hackaday: What Puts This Photo In The Pink?” →

Solar Light Shows Why Replacing NiMH With Li-Ion Is Dangerous

November 2, 2026 by 16 Comments

Recently [DiodeGoneWild] got his paws on a purportedly IP44-rated outdoor solar light with PIR motion sensor that also contains an 18650 Li-ion cell. Since it’s being sold in Czechia in a supermarket by a Czech company you’d expect it to meet at least some quality standards, but once he got inside the device a true horror show unfolded.

The best guess here is that someone took an originally cheap NiMH cell-based solar light circuit and simply replaced said NiMH cell with an – unprotected – Li-ion 18650 cell, as there is absolutely no charging management or cell protection. This is important as while NiMH will throttle charging current by rejecting it as heat the more it is in a charged state, Li-ion is not as tolerant.

Even ignoring that the ‘IP44’ enclosure has more gaps and holes in it than the average slice of Swiss cheese, the 5.5 V-rated PV solar panel happily tried charging the Li-ion cell at around 6 V. This raises the potential that on a particularly sunny day with an already charged Li-ion cell sitting at 4.2+ V, it’ll effectively grenade this cell.

During an outdoors test the 18650 cell was charged to 4.8 V before the sun vanished behind the building, which probably isn’t an amazing sign if you are expecting for this light to keep working for more than a few weeks. Or not violently explode/catch on fire on the side of your house for that matter.

Of course, treating a NiMH cell better than in this particular circuit will extend its lifespan as well, but the failure mode of that battery chemistry tends to be a bit less aggressive. Hence why people keep getting away with dodgy circuit designs like this.

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Looking For A Cellular Modem?

November 2, 2026 by 11 Comments

Cellular modems come and go, and they can be tricky beasts to tame – yet, in every portable computer project I’ve worked with, “LTE modem” has been a top-three request from the audience. If you’re building a cyberdeck or a general Linux portable, then a cellular modem’s cellular data uplink, SMS support, and even voice calls, can be the killer addition you need to make your deck a true daily machine. These days, I see that the demand for cyberdecks is rising, my own projects could greatly benefit from modems too, and yet it sometimes it feels like informational drought. I think now is a great time to make a listicle, detailing a few modems you should keep in mind.

Testing out prospective modems can be costly and time-intensive – design a board, purchase a few sample modems at inflated prices, only to have your idea completely blocked by elusive firmware issues at the very last step. I’ve given some starting-from-scratch tips before, having shown how to use mPCIe cards for testbench purposes. Today, I’d rather give you a few battle-tested modems that others already use with great success, and describe the features you can get out of one.

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Static Radio For The Chumby One

November 2, 2026 by 2 Comments

If you haven’t heard of Static Radio, it’s basically an online radio station made up of podcast content. [Brendan Fitzpatrick] decided to take an old 2009 Chumby One and turn it into an appliance for tuning in to Static.

This was achieved by creating a native C Static Radio client that could run on the Chumby’s 454 MHz ARM9 CPU. It’s got no FPU, only 60 MB of RAM, and runs Linux 2.6.28, so it’s not exactly the most up to date platform out there. But nevertheless, [Brendan] was able to make it work.

The client starts from a USB stick, without touching the original firmware on the Chumby itself. [Brendan] bundled in mbedTLS, since the stock Chumby OS shipped with OpenSSL 0.9.7 from 2004, which simply doesn’t cut it today. He also threw in a fixed-point Helix MP3 decoder along with HE-AAC and a polyphase resampler to handle sound, with the audio stream piped out to the kernel’s ALSA PCM device. The client is set up to buffer not only the current station, but the two neighbouring stations on the dial as well, so that turning the knob to switch stations comes with a clean crossfade transition.

If you’ve got a Chumby sitting around doing nothing, this could be the perfect way to put it back to work. We’ve examined other hacks for this venerable piece of hardware, too.

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A Hackable Analog Phone System

November 2, 2026 by 21 Comments

Do you have old landline phones laying around the house, with touchtone buttons or rotary dials? Perhaps you’d like to do something with them! [Scott Dylewski] has built hardware to let you do just that, since your local utility might have pulled down the lines already.

The Analog Redial is, essentially, a “little phone system you can hack,” according to [Scott]. Plug in a phone or two, and you get the functionality of yesteryear—a dial tone, ringing, and all that. You can make calls between the phones, out via a SIP server, or use the answering machine functionality. You can play around with settings via a web interface, or even set up dial codes so your phone can control your Home Assistant setup.

An ESP32-C6 does all the heavy lifting, with the aid of an ES8388 audio chip, and lets you plug in two phones for telephonic hijinks. You can even add a Bluetooth board to use your old landline as a handset for your modern smartphone. [Scott] has all the files on GitHub if you’d like to make one yourself, and you can get most of it pre-assembled by a board house if that’s your jam. It hardly gets easier than this.

We’ve featured other fun projects that repurpose old phones for new purposes, too. If you’re whipping up telecommunications witchery of your own in the home lab, be sure to notify our tipsline. Happy phonery!

Building The Stranger Things Lights For Halloween

November 1, 2026 by 1 Comment

When Stranger Things came out all those years ago, one image left an indelible mark on pop culture. A set of Christmas lights, lined up with letters of the alphabet, such that the kid who was barely in the show could blink out messages at Winona Rider from Topsy Turvy Town. [MyEmbeddedStuff] has recreated this cross-dimensional communication system for a fun Halloween project.

The build is basically a Xiao ESP32-S3 microcontroller board and a string of WS2812B addressable RGB LEDs. To keep the Christmas-lights aesthetic, they were actually assembled in place of non-addressable LEDs in a set of existing string lights, with two LEDs per letter of the alphabet for greater brightness adding up to 52 LEDs in total. Because the letters are only lit up one at a time, total current stays low, and power is easily drawn from the power input pin of the ESP32-S3. To control the display, there’s a web server running on the ESP32 which serves up a user interface for typing in messages and having them flash out in sequence, as they did in the show.

Most of the work was in cutting the letters out of EVA foam, but there’s nothing wrong with a quick Halloween arts and crafts project with the kids. It’s a fun decoration that can add a little vibe and curiosity to a Halloween party, so you might consider building something similar yourself next year.