Radio Apocalypse: America’s Doomsday Rocket Radios

Even in the early days of the Cold War, it quickly became apparent that simply having hundreds or even thousands of nuclear weapons would never be a sufficient deterrent to atomic attack. For nuclear weapons to be anything other than expensive ornaments, they have to be part of an engineered system that guarantees that they’ll work when they’re called upon to do so, and only then. And more importantly, your adversaries need to know that you’ve made every effort to make sure they go boom, and that they can’t interfere with that process.

In practical terms, nuclear deterrence is all about redundancy. There can be no single point of failure anywhere along the nuclear chain of command, and every system has to have a backup with multiple backups. That’s true inside every component of the system, from the warheads that form the sharp point of the spear to the systems that control and command those weapons, and especially in the systems that relay the orders that will send the missiles and bombers on their way.

When the fateful decision to push the button is made, Cold War planners had to ensure that the message got through. Even though they had a continent-wide system of radios and telephone lines that stitched together every missile launch facility and bomber base at their disposal, planners knew how fragile all that infrastructure could be, especially during a nuclear exchange. When the message absolutely, positively has to get through, you need a way to get above all that destruction, and so they came up with the Emergency Rocket Communication System, or ERCS.

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Dead Bug Timer Relay Needs No PCB

We often marvel at the many things a 555 can do. But [Zafer Yildiz] shows us that it can even take the place of a PCB. You’ll see what we mean in the video below. The timer relay circuit is built “dead bug” style with the 555 leads bent out to provide wiring terminals.

Honestly, these kinds of circuits are fun, but we would be reticent to use this type of construction for anything that had to survive in the real world. Solder joints aren’t known for being mechanically stable, so this is good for experiments, but maybe not something you want to do all the time.

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telescope mount

DIY Telescope Mount For Stellar Tracking

Pointing at stars may seem easy on the surface—just mount a telescope to a tripod and you’re done, right? As anyone who’s spent time with a telescope can tell you, it’s not that simple, given that the Earth is always spinning. [Sven] set out to make his own mount to compensate for the rotation of the Earth, which led to some pretty amazing results.

In this project, [Sven] designed a GoTo mount, which is a telescope equatorial mount capable of being pointed at specific parts of the sky and tracking them to allow for long-exposure photos with minimal blur due to the Earth’s movement. He first went down the path of finding the correct harmonic gearbox for the steppers used. A harmonic drive system would allow smooth, precise movement without backlash, and the 100:1 stepdown would provide for the slightest of adjustments.

The steppers are controlled by a custom PCB [Sven] designed around an ESP32-S3. The first PCB had a mistake in the power delivery circuit. After a small tweak, V2 boards arrived and work great. The PCB runs OnStepX, a great open-source project centered around pointing telescopes, cutting down a lot of the software workload on this project.

After all the work put in, you may be wondering how well it works. [Sven] was able to get a pointing accuracy of 1-2 arcseconds from his mount. To get an idea of how great that is, 1 arcsecond is about the same as pointing at a penny from 4 km (2.5 miles) away. Fantastic results, [Sven], and thank you for sending in this great project—be sure to head over to his site and read all the details of this impressive build. If you found this interesting, be sure to check out some of our other telescope-related projects.

A PLL For Perfect Pitch

When Hackaday runs a contest, we see all manner of clever projects. But inevitably there are some we don’t see, because their builders didn’t manage to get them finished in time. [Park Frazer]’s phase-locked loop is one of them. The circuit is an all-discrete PLL that derives a 440 Hz output from a 1 Hz input, and it arrived just too late for our 1 Hz contest.

If you aren’t familiar with a phase-locked loop, in this context you can think of them as a programmable frequency multiplier. A voltage-controlled oscillator is locked to an input frequency by comparing the two with a phase detector. Multiplication can be achieved by putting a frequency divider between the oscillator and the phase detector. It’s at the same time a complex and easy to understand circuit. In this case, when broken down into a set of multivibrators, it makes sense. The charge pump phase detector is a little different from the XOR gate we were expecting, but as he explains, it’s better.

If PLLs are a mystery, have a look at this video from a [Jeri Ellsworth] and [Bil Herd].

RP2040 Assembly Language Mix And Match

[David] is building a project with an OLED, a keyboard, and an RP2040. He’s perfected a scanning routine in C to work with the keyboard, but he still had some places he wanted to use even lower-level instructions. That was as good an excuse as any to experiment with inline assembly language inside the C program.

The goal was to grab the keyboard’s input and stick it into a memory address register so the data at that address could be shown on the display. However, there was a complication because memory access of this type has to be word-aligned.

Sure, you could mask the low bits of the address, do the read, and then set an index to pick the specific byte, but assembly is easy, and it is good to know how to put it in your code, anyway.

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Hackaday Links: August 24, 2025

“Emergency Law Enforcement Officer Hologram program activated. Please state the nature of your criminal or civil emergency.” Taking a cue from Star Trek: Voyager, the Seoul Metropolitan Police Agency is testing a holographic police officer, with surprisingly — dare we say, suspiciously? — positive results. The virtual officer makes an appearance every two minutes in the evening hours in a public park, presumably one with a history of criminal activity. The projection is accompanied by a stern warning that the area is being monitored with cameras, and that should anything untoward transpire, meat-based officers, presumably wearing something other than the dapper but impractical full-dress uniform the hologram sports, will be dispatched to deal with the issue.

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ESP32 bus pirate

ESP32 Sets Sail As A Modern Bus Pirate Powerhouse

Bus Pirate is nearly a household name in the hardware hacking world. The first version came out way back in 2008, and there have been several revisions since then. You can buy pre-built Bus Pirate devices, but there’s also the option now to build our own. The ESP32 Bus Pirate project has everything you need to turn an ESP32 device into a protocol sniffing/decoding powerhouse—all on a board you may have sitting around from another project.

There are a ton of solutions when it comes to talking to different buses —I2C, UART, JTAG, you name it, there’s a purpose-built device for it. Over a decade ago, Dangerous Prototypes released the Bus Pirate, offering a Swiss Army knife of a tool to interface with this ever-expanding list of communications standards. The ESP32 Bus Pirate project is open-source firmware for ESP32s that gives them the ability to be the multi-tool that lets us communicate with a long list of protocols.

It supports a wide variety of devices, from the straightforward ESP32 S3 Dev Kit available from a long list of suppliers to the more specialized M5 Cardputer equipped with its own keyboard. The original Bus Pirate required plugging the board into a PC to use it; with this being ESP32-based, that’s no longer a limitation. So long as you can supply power to the ESP32, you can connect and control it via WiFi and a web browser. In addition to the Bus Pirate protocols, the project allows us to directly control the pins on the ESP32 board, should you want to do more with it besides interfacing with one of the supported protocols. Be sure to check out some of our other articles about Bus Pirate, as it’s been a fantastic tool for the hacker community over the years.