hardware

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A photo of the thrust meter from the Apollo lunar module

Apollo Lunar Module Thrust Meter Lives Again

January 3, 2026 by No comments

[Mike Stewart] powers up a thrust meter from an Apollo lunar module. This bit of kit passed inspection on September 25, 1969. Fortunately [Mike] was able to dig up some old documentation which included the pin numbers. Score! It’s fun to see the various revisions this humble meter went through. Some of the latest revisions are there to address an issue where there was no indication upon failure, so they wired in a relay which could flip a lamp indicator if the device lost power.

This particular examination of this lunar thrust module is a good example of how a system’s complexity can quickly get out of hand. Rather than one pin there are two pins to indicate auto or manual thrust, each working with different voltage levels; the manual thrust is as given but the auto thrust is only the part of the thrust that gets added to a baseline thrust, so they need to be handled differently, requiring extra logic and wiring for biasing the thrust meter when appropriate. The video goes into further detail. Toward the end of the video [Mike] shows us what the meter’s backlights look like when powered.

If you’re interested in Apollo mission technology be sure to check out Don Eyles Walks Us Through The Lunar Module Source Code.

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Scientific staff members working on the computing machine Setun

The Setun Was A Ternary Computer From The USSR In 1958

January 3, 2026 by 24 Comments

[Codeolences] tells us about the FORBIDDEN Soviet Computer That Defied Binary Logic. The Setun, the world’s first ternary computer, was developed at Moscow State University in 1958. Its troubled and short-lived history is covered in the video. The machine itself uses “trits” (ternary digits) instead of “bits” (binary digits).

When your digits have three discrete values there are a multiplicity of ways of assigning meaning to each state, and the Setun uses a system known as balanced ternary where each digit can be either -1, 0, or 1 and otherwise uses a place-value system in the normal way.

An interesting factoid that comes up in the video is that base-3 (also known as radix-3) is the maximally efficient way to represent numbers because three is the closest integer to the natural growth constant, the base of the natural logarithm, e, which is approximately 2.718 ≈ 3.

If you’re interested to know more about ternary computing check out There Are 10 Kinds Of Computers In The World and Building The First Ternary Microprocessor.

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Interconnected circuits for controlling the clock

Tick, Tock, Train Station Clock

December 31, 2025 by 9 Comments

We’ve seen a few H-bridge circuits around these parts before, and here’s another application. This time we have an Old Train Station Clock which has been refurbished after being picked up for cheap at the flea market. These are big analog clocks which used to be common at railway stations around the world.

This build uses an ESP32 C3-mini microcontroller (PDF) in combination with an A4988 Microstepping Motor Driver (PDF). The logic is handled with MicroPython code. The A4988 provides two H-bridge circuits, one for each of two stepper motors, only one of which is used in this build.

The controller for this clock needs to send an alternating positive then negative DC pulse every minute to register that a minute has passed so the clock can update its hour hand and minute hand as appropriate. The ESP32 and the A4988 H-bridge cooperate to make that happen. The wifi on the ESP32 C3-mini is put to good use by facilitating the fetching of the current time from the internet. On an hourly basis the clock gets the current time with a HTTP call to a time server API, for whatever is suitable for your time zone.

Thanks to [PiotrTopa] for writing in to let us know about his project. If you’re interested in learning more about H-bridge applications be sure to check out Introduction To The H-bridge Motor Controller and A H-Bridge Motor Controller Tutorial Makes It Simple To Understand.

39C3: Hardware, And The Hard Bit

December 29, 2025 by 10 Comments

The 39th annual Chaos Communication Congress (39C3) is underway, and it kicked off with a talk that will resonate deeply with folks in the Hackaday universe. [Kliment] gave an impassioned invitation for everyone to start making hardware based on his experience both in the industry and in giving an intro-to-surface-mount workshop to maybe thousands of hackers over the years.

His main points are that the old “hardware is hard” cliche is overdone. Of course, working on a complicated high-reliability medical device isn’t child’s play, but that’s not where you start off. And getting started in hardware design and hobby-scale manufacture has never been easier or cheaper, and the open-source tooling gives you a foot in the door.

He tells the story of an attendee at a workshop who said “I kept waiting for the hard part to come, but then I was finished.”  Starting off with the right small-scale projects, learning a few techniques, and ramping up skills built on skills is the way to go. ([Kliment] is a big proponent of hand-placed hot-plate reflow soldering, and we concur.)

This is the talk that you want to show to your software friends who are hardware-curious. It’s also a plea for more experimentation, more prototyping, more hacking, and simply more people in the hardware / DIY electronics scene. Here at Hackaday, it’s maybe preaching to the choir, but sometimes it’s just nice to hear saying it all out loud.

A photo of the circuit on a breadboard

Retro Semiconductors: The Silicon Controlled Rectifier

December 28, 2025 by 9 Comments

Over on YouTube [Lockdown Electronics] reviews an old bit of kit known as the Silicon Controlled Rectifier (SCR). Invented in the 1950s the SCR is a type of thyristor and they were popular back in the 1970s. They are often replaced these days by the TRIAC and the MOSFET but you might still find some old schematics that call for them and you can still buy them.

The SCR is a three terminal electronic switch which latches on. You apply a signal at the gate which allows the other two pins, the anode and cathode, to conduct; and they continue to do so until power is removed. The silicon inside the device is comprised of three semiconductor junctions, as: PNPN. The P on the left is the anode, the N on the right is the cathode, and the P in the right middle is the gate.

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Cheetah 3d printer mobo

Cheetah MX4 Mini: A Pint-Sized 3D Printer Controller

December 28, 2025 by 31 Comments

There’s a seemingly unending list of modifications or upgrades you can make to a 3D printer. Most revolve around the mechanical side of things, many are simple prints or small add-ons. This upgrade is no small task: this 17-year-old hacker [Kai] took on designing and building his own 3D printer control motherboard, the Cheetah MX4 Mini.

He started the build by picking out the MCU to control everything. For that, he settled on the STM32H743, a fast chip with tons of support for all the protocols he could ask for, even as he was still nailing down the exact features to implement. For stepper drivers, [Kai] went with four TMC stepstick slots for silent motor control. There are provisions for sensorless homing and endstops, support for parallel and serial displays, and both USB-C and microSD card slots for receiving G-code. It can drive up to three fans as well as two high-amperage loads, such as for the heated bed.

All these features are packed into a board roughly the size of a drink coaster. Thanks to the STM32H743, the Cheetah MX4 Mini supports both Marlin and Klipper firmware, a smart choice that lets [Kai] leverage the massive amount of work that’s already gone into those projects.

One of the things that stood out about this project is the lengths to which [Kai] went to document what he did. Check out the day-by-day breakdown of the 86 hours that went into this build; reading through it is a fantastic learning aid for others. Thanks [JohnU] for sending in this tip! It’s great to see such an ambitious project not only taken on and accomplished, but documented along the way for others to learn from. This is a fantastic addition to the other 3D printer controllers we’ve seen.

off grid weather station

915 MHz Forecast: Rolling Your Own Offline Weather Station

December 19, 2025 by 9 Comments

There are a lot of options for local weather stations; most of them, however, are sensors tied to a base station, often requiring an internet connection to access all features. [Vinnie] over at vinthewrench has published his exploration into an off-grid weather station revolving around a Raspberry Pi and an RTL-SDR for communications.

The weather station has several aspects to it. The main sensor package [Vinnie] settled on was the Ecowitt WS90, capable of measuring wind speed, wind direction, temperature, humidity, light, UVI, and rain amount. The WS90 communicates at 915 MHz, which can be read using the rtl_433 project. The WS90 is also available for purchase as a standalone sensor, allowing [Vinnie] to implement his own base station.

For the base station, [Vinnie] uses a weatherproof enclosure that houses a 12V battery with charger to act as a local UPS. This powers the brains of the operation: a Raspberry Pi. Hooked to the Pi is an RTL-SDR with a 915 MHz antenna. The Pi receives an update from the WS90 roughly every 5 seconds, which it can decode using the rtl_433 library. The Pi then turns that packet into structured JSON.

The JSON is fed into a weather model backend that handles keeping track of trends in the sensor data, as well as the health of the sensor station. The backend has an API that allows for a dashboard weather site for [Vinnie], no internet required.

Thanks, [Vinnie], for sending in your off-grid weather station project. Check out his site to read more about his process, and head over to the GitHub page to check out the technical details of his implementation. This is a great addition to some of the other DIY weather stations we’ve featured here.