Musical Proximity Detection Pet Bowls

An essential skill for a maker is the ability to improvise or re-purpose existing materials into new parts. Sometimes, one needn’t make many modifications to create something new, as is the case with [Robin Sterling] and his musical pet bowl.

Originally, it was a sealed pet bowl that opened when the proximity sensors detected an approaching pet. Having helped design the bowl, [Sterling] had a bit of an advantage when he decided to convert it into a theremin/light harp-esque instrument for the company BBQ. He routed the PWM outputs from each of the three proximity sensors (in each of the three bowls) to a small guitar amp, adjusting each sensor’s output to a different frequency. Despite the short amount of time [Sterling] had to practice, it works fairly well!

Continue reading “Musical Proximity Detection Pet Bowls”

Amazing Carbon Foam Doesn’t Take Much Bread

A lot of people knew the Space Shuttle had ceramic tiles to protect its nose from reentry heat. That’s mostly because the tiles fell off a lot and each one was a unique shape, so it got a lot of press coverage. However, you didn’t hear as much about the parts of the orbiter that got really hot: the forward part of the wings and the tip of the nose. For those, NASA used an exotic material called RCC or reinforced carbon-carbon. Other uses include missile nose cones and Formula One brakes. A similar material, carbon fiber-reinforced silicon carbide appears in some high-end car brakes. These materials can take high temperatures, easily.

[AvE] wanted to make some carbon foam for experiments. It does take a little bread, though. Not money, but literal bread. To create the foam, he burns bread slices in a chamber full of argon. The stuff has some amazing properties.

In the video below, you can see the foam protecting a thermocouple from a torch flame and even holding melting aluminum. Not bad for a few pieces of bread.

Continue reading “Amazing Carbon Foam Doesn’t Take Much Bread”

The Mystery Behind the Globs of Epoxy

When Sparkfun visited the factory that makes their multimeters and photographed a mysterious industrial process.

We all know that the little black globs on electronics has a semiconductor of some sort hiding beneath, but the process is one that’s not really explored much in the home shop.  The basic story being that, for various reasons , there is no cheaper way to get a chip on a board than to use the aptly named chip-on-board or COB process. Without the expense of encapsulating  the raw chunk of etched and plated silicon, the semiconductor retailer can sell the chip for pennies. It’s also a great way to accept delivery of custom silicon or place a grouping of chips closely together while maintaining a cheap, reliable, and low-profile package.

As SparkFun reveals, the story begins with a tray of silicon wafers. A person epoxies the wafer with some conductive glue to its place on the board. Surprisingly, alignment isn’t critical. The epoxy dries and then the circuit board is taken to a, “semi-automatic thermosonic wire bonding machine,” and slotted into a fixture at its base. The awesomely named machine needs the operator to find the center of the first two pads to be bonded with wire. Using this information it quickly bonds the pads on the silicon wafer to the  board — a process you’ll find satisfying in the clip below.

The final step is to place the familiar black blob of epoxy over the assembly and bake the board at the temperature the recipe in the datasheet demands. It’s a common manufacturing process that saves more money than coloring a multimeter anything other than yellow.

Continue reading “The Mystery Behind the Globs of Epoxy”

Rainy Day Fun by Calculating Pi

If you need a truly random event generator, just wait till your next rainstorm. Whether any given spot on the ground is hit by a drop at a particular time is anyone’s guess, and such randomness is key to this simple rig that estimates the value of pi using raindrop sensors.

You may recall [AlphaPhoenix]’s recent electroshock Settlers of Catan expeditor. The idea with this less shocking build is to estimate the value of pi using the ratio of the area of a square sensor to a circular one. Simple piezo transducers serve as impact sensors that feed an Arduino and count the relative number of raindrops hitting the sensors. In the first video below, we see that as more data accumulates, the Arduino’s estimate of pi eventually converges on the well-known 3.14159 value. The second video has details of the math behind the method, plus a discussion of the real-world problems that cropped up during testing — turns out that waterproofing and grounding were both key to noise-free data from the sensor pads.

In the end, [AlphaPhoenix] isn’t proving anything new, but we like the method here and can see applications for it. What about using such sensors to detect individual popcorn kernels popping to demonstrate the Gaussian distribution? We also can’t help but think of other ways to measure raindrops; how about strain gauges that weigh the rainwater as it accumulates differentially in square and circular containers? Share your ideas in the comments below.

Continue reading “Rainy Day Fun by Calculating Pi”

Compact ePaper Business Card

Is your business card flashy? Is it useful in a pinch? Do they cost $32 each and come with an ePaper display? No? Well, then feast your eyes on this over-the-top business card with an ePaper display by [Paul Schow]. Looking to keep busy and challenge himself with a low-power circuit in a small package, he set about making a business card that can be updated every couple of months instead of buying a new stack whenever he updated his information.

Having worked with ePaper before, it seemed to be the go-to option for [Schow] in fulfilling the ultra-low power criteria of his project — eventually deciding on a 2″ display. Also looking to execute this project at speed, he designed the board in KiCad over a few hours after cutting it down to simply the power control, the 40-pin connector and a handful of resistors and capacitors. In this case, haste made waste in the shape of the incorrect orientation of the 40-pin connector and a few other mistakes besides. Version 2.0, however, came together as a perfect proof-of-concept, while 3.0 looks sleek and professional.

Continue reading “Compact ePaper Business Card”

Building A DIY Heat Pipe

Once the secret design tool for aerospace designers, the heat pipe is a common fixture now thanks to the demands of PC CPU cooling. Heat pipes can transfer lots of energy from a hot side to a cold side and is useful when you need to cool something where having a fan near the hot part isn’t feasible for some reason. Unlike active cooling, a heat pipe doesn’t require any external power or pumps, either.

[James Biggar] builds his own heat pipes using copper tubing. You can see a video of one being made, below. There’s not much to it, just a copper pipe with some water in it. However, [James] gets the water boiling to reduce the pressure in the tube before sealing it, which is an interesting trick.

One limitation of his technique is that there is no internal wick. That means the tube can only be installed vertically. If you haven’t looked at heat pipes before, most of them do have a wick. The idea is that some working fluid is in the pipe. You select that fluid so that it boils at or below the temperature you want to handle. The hot vapor rushes to the cool side of the pipe (carrying heat) where you have a large heatsink that may have a fan or active cooling system. The vapor condenses and–in this case–drops back to the bottom of the tube. However, if there is a wick, capillary action will return the fluid to the hot end of the tube.

You might think that using water as the working fluid would limit you to 100°C, but remember, [James’] technique lowers the pressure in the tube. At a lower pressure, the water will boil at a lower temperature.

We’ve seen heat pipes and wine chillers used to cool a PC before. In fact, we’ve even seen them in builds of completely fanless PCs.

Continue reading “Building A DIY Heat Pipe”

Laser-Cut ArcSin Dress Is Wearable Math

Using sewing simulation, 3D modeling and laser-cutting [Nancy Yi Liang] makes custom dresses that fit like a glove. Her project documentation walks us through all the steps from the first sketch to the final garment.

After sketching the design on paper, the design process moves into the digital domain, where an accurate 3D model of the wearer is required. [Nancy] created hers with Make Human, a free software that creates to-size avatars of humans from tape-measured parameters. Using the professional garment modeling software MarvelousDesigner (which offers a 30 day trial version), she then created the actual layout. The software allows her to design the cutting patterns, and then also drapes the fabric around the human model in a 3D garment simulation to check the fit. The result are the cutting patterns and a 3D model of the garment.

Continue reading “Laser-Cut ArcSin Dress Is Wearable Math”