HackadayModify

2026-01-19 11:00:59

For switching high-powered loads from a microcontroller, or for switching AC loads in general, most of us will reach into the parts bin and pull out a generic relay of some sort. Relays are fundamental, proven technologies to safely switch all kinds of loads. They do have their downsides, though, so if you need silent operation, precise timing, or the ability to operate orders of magnitude more times you might want to look at a triac instead. These solid state devices can switch AC loads unlike other transistor-based devices and [Ray] at OpenSprinkler is here to give us an overview on how to use them.

The key to switching an AC load is bi-directional conductivity. A normal transistor or diode can only conduct in one direction, so if you try to switch an AC load with one of these you’ll end up with what essentially amounts to a bad rectifier. Triacs do have a “gate” analogous to the base of a bipolar junction transistor, but the gate will trigger the triac when current flows in either direction as well. The amount of current needed to trigger the triac does depend on the state of the switched waveform, so it can be more complex to configure than a relay or transistor in some situations.

After going through some of the theory around these devices, [Ray] demonstrates how to use them with an irrigation system, which are almost always operating on a 24VAC system thanks to various historical quirks. This involves providing the triacs with a low voltage source to provide gate current as well as a few other steps. But with that out of the way, switching AC loads with triacs can become second nature. If you prefer a DC setup for your sprinklers, though, [vinthewrench] has demonstrated how to convert these sprinkler systems instead.

2026-01-19 08:00:20

Looking for a unique vacation spot? Have at least $10 million USD burning a hole in your pocket? If so, then you’re just the sort of customer the rather suspiciously named “GRU Space” is looking for. They’re currently taking non-refundable $1,000 deposits from individuals looking to stay at their currently non-existent hotel on the lunar surface. They don’t expect you’ll be able to check in until at least the early 2030s, and the $1K doesn’t actually guarantee you’ll be selected as one of the guests who will be required to cough up the final eight-figure ticket price before liftoff, but at least admission into the history books is free with your stay.

The whole idea reminds us of Mars One, which promised to send the first group of colonists to the Red Planet by 2024. They went bankrupt in 2019 after collecting ~$100 deposits from more than 4,000 applicants, and we probably don’t have to tell you that they never actually shot anyone into space. Admittedly, the Moon is a far more attainable goal, and the commercial space industry has made enormous strides in the decade since Mars One started taking applications. But we’re still not holding our breath that GRU Space will be leaving any mints on pillows at one-sixth gravity.

Speaking of something which actually does have a chance of reaching the Moon on time — on Saturday, NASA rolled out the massive Space Launch System (SLS) rocket that will carry a crew of four towards our nearest celestial neighbor during the Artemis II mission. There’s still plenty of prep work to do, including a dress rehearsal that’s set to take place in the next couple of weeks, but we’re getting very close. Artemis II won’t actually land on the Moon, instead performing a lunar flyby, but it will still be the first time we’ve sent humans beyond Low Earth Orbit (LEO) since Apollo 17 in 1972. We can’t wait for some 4K Earthrise video.

In more terrestrial matters, Verizon users are likely still seething from the widespread outages that hit them mid-week. Users from all over the US reported losing cellular service for several hours, though outage maps at the time showed the Northeast was hit particularly hard. At one point, the situation got so bad that Verizon’s own system status page crashed. In a particularly embarrassing turn of events, some of the other cellular carriers actually reached out to their customers to explain it wasn’t their fault if they couldn’t reach friends and family on Verizon’s network. Oof.

Speaking of phones, security researchers recently unveiled WhisperPair, an attack targeting Bluetooth devices that utilize Google’s Fast Pair protocol. When the feature is implemented correctly, a Bluetooth accessory should ignore pairing requests unless it’s actually in pairing mode, but the researchers found that many popular models (including Google’s own Pixel Buds Pro 2) can be tricked into accepting an unsolicited pairing request. While an attacker hijacking your Bluetooth headset might not seem like a huge deal at first, consider that it could allow them to record your conversations and track your location via Google’s Find Hub network.

Incidentally, something like WhisperPair is the kind of thing we’d traditionally leave for Jonathan Bennett to cover in his This Week in Security column, but as regular readers may know, he had to hang up his balaclava back in December. We know many of you have been missing your weekly infosec dump, but we also know it’s not the kind of thing that just anyone can take over. We generally operate under a “Write What You Know” rule around here, and that means whoever takes over the reins needs to know the field well enough to talk authoritatively about it. Luckily, we think we’ve found just the hacker for the job, so hopefully we’ll be able to start it back up in the near future.

Finally, we don’t generally promote crowdfunding campaigns due to their uncertain nature, but we’ll make an exception for the GameTank. We’ve covered the open hardware 6502 homebrew game console here in the past, and even saw it in the desert of the real (Philadelphia) at JawnCon 0x2 in October. The project really embraces the retro feel of using a console from the 1980s, even requiring you to physically swap cartridges to play different games. It’s a totally unreasonable design choice from a technical perspective, given that an SD card could hold thousands of games at once, but of course, that’s not the point. There’s a certain joy in plugging in a nice chunky cartridge that you just can’t beat.

See something interesting that you think would be a good fit for our weekly Links column? Drop us a line, we’ve love to hear about it.

2026-01-19 05:00:18

When [Electron Impressions] used a powerful ultrasonic array to project a narrow beam of sound toward a target, he described it as potentially useful in getting someone’s attention from across a crowded room without disturbing other people. This is quite a courteous use compared to some of the ideas that occur to us, and particularly compared to the crowd-control applications that various militaries and police departments put directional speakers to.

Regardless of how one uses it, however, the physics behind such directional speakers is interesting. Normal speakers tend to disperse their sound widely because the size of the diaphragm is small compared to the wavelength of the sound they produce; just like light waves passing through a pinhole or thin slit, the sound waves diffract outwards in all directions from their source. Audible frequencies have wavelengths too long to make a handheld directional speaker, but ultrasonic waves are short enough to work well; [Electron Impressions] used 40 kHz, which has a wavelength of just eight millimeters. To make the output even more directional, he used an array of evenly-spaced parallel emitters, which interfere constructively to the front and destructively to the sides.

Ultrasound shouldn’t be audible, but sound waves travel slightly faster in high-pressure air than in low-pressure air. Since sound waves are just variations in pressure, this means that at high enough amplitudes, they change their own shape as they travel through air, tending to merge together somewhat into lower-frequency waves. When amplitude modulation is applied to the ultrasonic signal, the air itself demodulates it into audible sound (the audio quality isn’t wonderful, but still recognizable). [Electron Impressions] demonstrated the completed device, and it’s possible to hear a clear difference in intensity when it’s pointed at the microphone. It’s also possible to reflect the sound beam off hard surfaces, though multiple reflections tend to decrease the directivity when used indoors.

The circuit itself is very similar to another which we’ve covered before, down to the 555 timer used in the ultrasonic driver, and the overall approach is very reminiscent of this directional ultrasonic array.

2026-01-19 02:00:11

Professional mountain bike racing is a rather bizarre sport. At the highest level, times between podiums will be less than a second, and countless hours of training and engineering go into those fractions of seconds. An all too important tool for the world cup race team is data acquisition systems (DAQ). In the right hands, they can offer an unparalleled suspension tune for a world cup racer. Sadly DAQs can cost thousands of dollars, so [sghctoma] built one using little more then potentiometer and LEGO. 

The hardware is a fairly simple task to solve. A simple Raspberry Pi Pico setup is used to capture potentiometer data. By some simple LEGO linkage and mounts, this data is correlated to the bikes’ wheel travel. Finally, everything is logged onto an SD card in a CSV format. Some buttons and a small AMOLED provide a simple user interface wrapped in a 3D printed case.

Analyzing the data is a rather daunting task. The entire analysis framework is neatly wrapped into a web server. The DAQ can automatically sync with the web interface, and provide suspension metrics in conjunction with action camera footage and a GPS track for further analysis.

However, not all is as it seems when it comes to correlating the suspension data into such a nice UI. A key issue is that with four bar, or even six bar, mountain bike linkage designs, the leverage ratio applied to the shock changes through the wheels travel. That means, when measuring shock travel, it needs to be adjusted to find wheel travel according to manufacturer specifications.

You need to be a bit of a suspension wizard to make sense of the charts. Nevertheless, for the mountain biking hackers out there, everything is available on Github, so if you wish to analyze suspension performance, make sure to check it out!

This isn’t the first time we have seen mountain bike data loggers, make sure to check out this simple Arduino build next! 

2026-01-18 23:00:15

In an update video by [Hacker University] to an earlier video on ESP32-C3 Super Mini development boards that feature a Flash-less version of this MCU, the question of adding your own Flash IC to these boards is addressed. The short version is that while it is possible, it’s definitely not going to be easy, as pins including SPIHD (19) and SPICLK (22) and SPIQ (24) are not broken out on the board and thus require one to directly solder wires to the QFN pads.

Considering how sketchy it would be to have multiple wires running off to an external Flash IC, this raises many questions about the feasibility, as well as cost-effectiveness. Some in the comments to the video remark that instead you may as well swap the MCU with a version that does contain built-in Flash, but this is countered with the argument that a new ESP32-C3 Super Mini board with the right MCU costs as much as a loose MCU from your favorite purveyor of ICs.

Ultimately this lends some credence to calling these zero Flash Super Mini boards a ‘scam’, as their use cases would seem to be extremely limited and their Flash-less nature very poorly advertised.

2026-01-18 20:00:47

[Dr Ali Shirsavar] from Biricha Digital runs us through How to Select the Perfect Output Capacitor for Your Power Supply. Your switching-mode power supply (SMPS) will require an output capacitor both to iron out voltage swings due to loading and to attenuate ripple caused by switching. In this video we learn how to calculate the required capacitance, and when necessary the ESR, for your output capacitor.

To begin [Dr Ali] shows us that in order to calculate the minimum capacitance to mitigate voltage swings we need values for Δi, Δv, and T_s. Using these we can calculate the minimum output capacitance. We then need to calculate another minimum capacitance for our circuit given that we need to attenuate ripple. To calculate this second minimum we need to change our approach depending on the type of capacitor we are using, such as ceramic, or electrolytic, or something else.

When our circuit calls for an electrolytic capacitor the equivalent series resistance (ESR) becomes relevant and we need to take it into account. The ESR is so predominant that in our calculations for the minimum capacitance to mitigate ripple we can ignore the capacitance and use the ESR only as it is the feature which dominates. [Dr Ali] goes into detail for both examples using ceramic capacitors and electrolytic capacitors. Armed with the minimum capacitance (in Farads) and maximum ESR (in Ohms) you can then go shopping to find a capacitor which meets the requirements.

If you’re interested in capacitors and capacitance you might enjoy reading about Measuring Capacitance Against Voltage and Getting A Handle On ESR With A Couple Of DIY Meters.