There probably aren’t many people out there who aren’t aware of what thermite is and how it demonstrates the power of runaway exothermic reactions. Practical applications that don’t involve destroying something are maybe less known. This is where the use of thermite for creating welds is rather interesting, as shown in this video by [Finn] that is also embedded after the break.

In the video, one can see how [Finn] uses thermite charges to weld massive copper conductors together in a matter of seconds inside a graphite mold. Straight joints, T-joints, and others are a matter of putting the conductors into the mold, pushing a button and watching the fireworks. After a bit of cleaning the slag off, a solid, durable weld is left behind.

The official name for this process is ‘exothermic welding‘, and it has been in use since the 19th century. Back then it was used primarily for rail welding. These days it sees a lot of use in high-voltage wiring and other applications, as in the linked video. The obvious advantage of exothermic welding is that the resulting joint is strong and durable, on account of the two surfaces having been permanently joined.

source https://hackaday.com/2020/07/30/enjoying-some-exothermic-welding-with-thermite/

We are fortunate to live in an age surrounded by means of easy communication, and like never before we can have friends on the other side of the world as well as just down the road. But as many readers will know, this ease of communication comes at a price of sharing public and commercial infrastructure. To communicate with privacy and entirely off-grid remains an elusive prize, but it’s one pursued by Scott Powell with his LoRa QWERTY Messenger. This is a simple pager device that forms a LoRa mesh network with its peers, and passes encrypted messages to those in the same group.

At its heart is a LoRa ESP32 module with a small OLED display and a Blackberry QWERTY keyboard, and an SD card slot. The device’s identity is contained on an SD card, which gives ease of reconfiguration. It’s doubly useful, because it is also a complement to his already existing Ripple LoRa communication project, that uses a smartphone as the front end for a similar board.

We feel this type of secure distributed communication is an exciting application for LoRa, whether it be for kids playing at being spies or for more serious purposes. It’s certainly not the first such project we’ve featured.

source https://hackaday.com/2020/07/30/join-your-own-private-lora-mesh-network/

The 8721 PLA, or programmable logic array, was one of the chips that had to be invented to make the Commodore 128, the last of the 8-bit computers that formed the leading edge of the early PC revolution, a reality. [Johan Grip] got a hold of one of these chips and decided to reverse engineer it, to see what the C-128 designers had in mind back in mid-1980s.

PLAs were the FPGAs of the day, with arrays of AND gates and OR gates that could be connected into complex logic circuits. [Johan]’s investigation started with liberating the 8721 die from its package, for which he used the quick and easy method favored by [CuriousMarc]. The next step was tooling up, as the microscope he was using proved insufficient to the task. Even with a better microscope in hand, [Johan] still found the need to tweak it, adding one of the new high-quality Raspberry Pi cameras and motorizing the stage with some stepper motors and a CNC controller board.

With optics sorted out, he was able to identify all the pads on the die and to find the main gate array areas. Zooming in a little further, he was able to see the connections between the matrices of the AND and OR gates, which makes decoding the logic a relative snap, although the presence of what appears to be an output block with latching functions confounds this somewhat.

The end result is a full Verilog HDL file that reflects the original 8721 logic, which we think is a pretty neat trick. And we’d love it if our own [Bil Herd] could chime in on this; after all, he literally designed the C-128.

source https://hackaday.com/2020/07/29/die-photos-reveal-logic-from-commodore-128-pla-chip/

One of the best things about the Internet — especially the video part — is that you can get exposed to lots of things you might otherwise not be able to see. Take oscilloscopes, for example. If you were lucky, you might have one or two really nice instruments at work and you certainly weren’t going to be allowed to tear them open if they were working well. [The Signal Path], as a case in point, tears down a $30,000 MSO6 8 GHz oscilloscope.

Actually, the base price is not quite $30,000 but by the time you outfit one, you’ll probably break the $30K barrier. Compared to the scopes we usually get to use, these are very different. Sure, the screens are larger and denser, but looking at the circuit boards they look more like some sort of high-end computer than an oscilloscope. Of course, in a way, that’s exactly what it is.

The real trick to building an expensive 8 GHz is the signal integrity. But the most visible part of the design is thermal management. The entire box is full of heat sinks and other thermal management gear.

The board inside actually can accommodate six inputs, even though the scope was only set up for four inputs. No software hack here, though. The boards are lacking the connectors and the special ICs that manage the front end.

The video is nearly an hour long, and goes into a lot of detail. Looking at the analog front end design is surprisingly enlightening, especially since there are two unpopulated sections so you can deduce the wiring easily without removing any parts.

We used to think we were in clover buying surplus Tektronix or HP scopes from the 1970s back in the 1990s. We wonder how long it will be before these become staples at hamfests and on eBay?

If you want to contrast that to a more common scope, look at the insides of this OWON.You can also shop for something more affordable if you are in the market. Just don’t expect it to look or perform like this scope!

source https://hackaday.com/2020/07/29/inside-a-30000-8-ghz-scope/

What’s the coolest thing you could build for a Harry Potter fan, aside from a working magic wand or Quidditch broomstick? We would have to say a Weasley clock that shows the whereabouts of everyone in the family is pretty high on the list, especially if that fan is a wife and mother.

Here’s how it works: they’ve set up geofences to define the boundaries of home, each person’s school or workplace, and so on. The family’s locations are tracked through their phones’ GPS using Home Assistant, which is hosted on a Raspberry Pi. Whenever someone’s location changes, the Pi alerts the clock over MQTT, and it moves the 3D-printed hands with servos.

The clock has some interesting granularity to it as well. As someone gets closer to home, their pointer’s distance reflects that in its proximity to the Home slice. And Home itself is divided into the main house and the shop and reflected by the pointer’s position.

We particularly like the attention to detail here, like the art poster used for the clock’s face that includes all the Weasley’s whereabouts in the background. It’s built into a thrift store grandmother clock, which is smaller than a grandfather clock but no less majestic. In the future there are plans to implement the clock’s chimes to announce that someone is back home.

No matter what you’re into, the whereabouts clock idea can probably fit that universe. For instance, here’s one that uses LEGO mini-fig heads to locate roommates.

source https://hackaday.com/2020/07/29/do-you-know-where-your-children-are-check-the-weasley-clock/

What’s the coolest thing you could build for a Harry Potter fan, aside from a working magic wand or Quidditch broomstick? We would have to say a Weasley clock that shows the whereabouts of everyone in the family is pretty high on the list, especially if that fan is a wife and mother.

Here’s how it works: they’ve set up geofences to define the boundaries of home, each person’s school or workplace, and so on. The family’s locations are tracked through their phones’ GPS using Home Assistant, which is hosted on a Raspberry Pi. Whenever someone’s location changes, the Pi alerts the clock over MQTT, and it moves the 3D-printed hands with servos.

The clock has some interesting granularity to it as well. As someone gets closer to home, their pointer’s distance reflects that in its proximity to the Home slice. And Home itself is divided into the main house and the shop and reflected by the pointer’s position.

We particularly like the attention to detail here, like the art poster used for the clock’s face that includes all the Weasley’s whereabouts in the background. It’s built into a thrift store grandmother clock, which is smaller than a grandfather clock but no less majestic. In the future there are plans to implement the clock’s chimes to announce that someone is back home.

No matter what you’re into, the whereabouts clock idea can probably fit that universe. For instance, here’s one that uses LEGO mini-fig heads to locate roommates.

source https://hackaday.com/2020/07/29/do-you-know-where-your-children-are-check-the-weasley-clock/