When the guys at [Practical Engineering] say they have a dirty car stand, they really mean it! They made a block of dirt and sheets of fiberglass as reinforcement material, and the resistance was put to test by using it as a car stand. And yes, the block does the job without collapsing.
Soil is a naturally unstable material, it relies only on friction for structural stability, but it has a very low shear strength (the resistance of the material’s internal structure to slide against itself). Therefore, as soon as you put some weight, a soil structure fails. The trick is to form a composite by adding layers of a stiff material. Those layers increase the shear strength and you end up with an incredibly strong composite, or ‘mechanically stabilized earth‘ (MSE). You probably drive by some everyday, as in the picture at the right.
Even though the modern form of MSE was due to French engineer Sir Henri Vidal, reinforced soil has been used since the beginnings of human history, in fact, some sections of the Great Wall of China were made using this technique. [Practical Engineering] explanation and demonstration video is very well made, be sure to check it after the break. In case you don’t want to play with dirt next time you need to fix your car, you can always make a 3D printed jack.
In material science, thermal expansion is a very well understood concept. However, in most cases it’s regarded as somewhat of a nuisance. It’s the kind of thing that gives engineers headaches, and entire subsystems of machines are often designed specifically to combat it. But a group of students at MIT have come up with an ingeniously simple way of taking advantage of thermal expansion to create shape-changing composites.
Their project is a method of creating shape-shifting composites, called uniMorph. It works by using resistive heating (or simply ambient temperature) to change the temperature of a sandwich composite. The composite is made of two different materials, and the copper traces to heat them. The two materials themselves aren’t particularly important, what’s important is that they have vastly different thermal expansion rates.
When the composite is heated, one material will expand more or less than the other material. Depending on the relative shapes of the two materials, this causes the composite to bend or twist in predetermined ways. How much it bends, for example, is just a matter of how the layers are cut, and how much they’re heated.
The concept itself isn’t exactly new – bimetallic composites have existed for ages. We even covered a similar idea that works based on moisture content. But, the methods used for uniMorph are very well thought out. It’s very inexpensive to produce, and the students seem to have devised reliable techniques for designing the layers in order to produce a desired shape change.
No, your eyes do not deceive you. That’s a wrist-mounted PDA. Specifically, a Fossil Wrist PDA, also known as an Abacus, that was sold from 2003 to about 2005. Yep, it’s running PalmOS. [mclien] has had this watch/PDA for a while now, and found the original 180mAh battery wasn’t cutting it anymore. He made a little modification to the watch to get a 650mAh battery in this PDA by molding a new back for it.
The original PDA used a round Lithium cell, but being ten years old, the battery technology in this smart watch is showing its years. [mclien] found two batteries (380mAh and 270mAh) that fit almost perfectly inside the battery.
The new batteries were about 3mm too thick for the existing case back, so [mclien] began by taking the old case, adding a few bits of aluminum and resin, and making a positive for a mold. Two or three layers of glass twill cloth were used to form the mold, resined up, and vacuum bagged.
After many, many attempts, [mclien] just about has the case back for this old smartwatch complete. The project build logs are actually a great read, showing exactly what doesn’t work, and are a great example of using hackaday.io as a build log, instead of just project presentation.
[GK] has a bit of a fetish for old oscilloscopes, and since he’s using an old ‘scope tube, the design was rather simple for him; there aren’t any schematics here, just what he could put together off the top of his head.
Still, some of [GK]’s earlier projects helped him along the way in turning this CRT into a monitor. The high voltage came from a variable output PSU he had originally designed for photomultiplier tubes. Since this is a monochrome display, the chrominance was discarded with an old Sony Y/C module found in a part drawer.
It’s a great piece of work that, in the words of someone we highly respect is, “worth more than a gazillion lame Hackaday posts where someone connected an Arduino to something, or left a breadboard in a supposedly “finished” project.” Love ya, [Mike].
The first three minutes of the video after the break are devoted to the video display hack. He starts with a glimpse of the breadboard circuit which takes the composite video signal and provides the necessary X, Y, and Z input signals to the scope to perform like this. He then walks through each portion of the schematic, which is based on an LM1881 video sync separator chip. The horizontal and vertical sync signals are separated by this chip, then filtered to produce ramp voltages for each to drive X and Y. The Z-axis is fed through a simple inverter circuit; Bob’s your uncle and your oscilloscope is now a TV monitor.
Of course this is not the first time this has been done. But we loved [Alan’s] presentation, and thought the shop tour was a fun way to finish off the video.
[NatureTM] used part of the Thanksgiving holiday to get composite video output working with an MSP430 microcontroller. He’s using one of the chips that came with the TI Launchpad, which is a big hardware limitation because of the relatively small code memory and RAM. The chip displays one still image at a resolution of 192×40 pixels. Still, this is a great way to learn about composite video signals, as a lot of other projects use a TVout library to save you the headaches. All you’ll need is a TI Launchpad, a 16 MHz crystal oscillator, two resistors, and an RCA jack. Dig through the code and see what a great job [NatureTM] did of offloading as much work onto the chip’s peripherals as possible.
[Ben Krasnow] is capturing some great snapshots using a microscope adapter and some tricks. The camera attachment is just a lens adapter ring with a tube added. Unlike other microscope imaging hacks we’ve seen he used a real microscope but found that the pictures had a bit of light distortion to them. The camera sensor was picking up a glare reflected on the inside of the black tube. By adding a washer and repositioning the apparatus he got over that hurdle. The final part of the puzzle is image processing. By taking several pictures at different focal lengths and compositing them he gets killer photos like the compound eyes of that house fly seen above.