Retrotechtacular: History of the U.S. Antiballistic Missile Systems


On this installment of Retrotechtacular we’re taking a look at the history of the United States Antiballistic Missile System. The cold war was a huge driver of technological development, and this missile defense is a good example. At its most basic this is a radar system capable of tracking objects in three dimensions. It utilizes separate transmitters and receivers which are synchronized to rotate at the same time.

The movie, which is about forty-five minutes, came to our attention because of [Dammitd’s] interest in the Luneburg Lens used by the system. At about 11:10 into the video after the break this component is discussed. Inside a dome like the one seen above is a reflector made of blocks of polystyrene foam which has been laced with bits of metal. This lens is stationary, with the receiver rotating around it to collect the transmitter’s waves as the echos bouncing off an object in the sky are focused by the lens.

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Sump pump alarm sends text message as water rises


We’ve got some friends who have two sump pumps. One is a backup and sounds an alarm when it is switched on. But this only works as long as they’re home to hear it. [Felix Rusu] came up with a solution what will text him if the sump pump fails. This way he can head home, or call someone to check in on the problem if he’s away.

We saw a pretty complicated monitoring system back in January. This one uses a single ultrasonic rangefinder which we think is much simpler. It’s accurate to about 1cm and is simple to use — it’s very popular with the hobby electronics crowd which helps with price and availability of sample code. We hem and haw about the use of a Raspberry Pi board with the project. On the one hand it’s a cheap way to get the sensor on the network and provides the infrastructure you need to send any number of alerts. On the other hand, it’s a lot of power for this particular application. But we figure it can be extended to monitor other utilities in [Felix’s] home, like a sensor to alert him of a leaking water heater. And we think everyone can argue that a monitor like this is well worth the time and effort he spent to develop it.

Scratch-built 3D printer shows rock-solid performance


These days it’s super-easy (not super-cheap) to go out and buy a 3D printer. But if you’ve got the mad skills like [Mario Lukas] maybe you can build a 3D print using a bunch of scavenged parts (translated). He’s published six posts on the build, and put together an overview video which you can watch after the break.

A pile of salvaged parts were found in a scanner and four different printers. He’s also powering the thing with an old PC PSU. The hot bed and extruder are brand new, which is a wise investment. We’re not sure about the threaded rod and bearings but we’d bet those are new as well. When it came time to work on the electronics he chose an Arduino board as the go-between for the printer and computer. It uses four stepper motor driver boards to drive the axes. Connections can be a bit complicated and he actually ‘smoked’ one of the boards during the development phase.

One of the mechanical build posts shows a belt routed in a T-shape. We wonder if it’s function is similar to what this H-bot style printer uses?

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