Microstepping a stepper motor with the SLA7062

Stepper motors can be made to rotate more smoothly by providing simulated sine waves. The SLA7062 chip uses internal PWM to provide sinusoidal current waveforms to unipolar stepper motors. I have this working fairly well, but the PWM frequency is acoustically apparent and annoying.

How to TIG weld aluminum beverage cans together

I show how to weld aluminum cans together with a cheap import TIG welder. I am not a professional welder, so some of my advice may be unconventional or even wrong, but these methods work well for me. With a 3/32" electrode and large gas lens, I don't have to change the torch setup for nearly any kind of common welding. Let me know if you have any questions or would like me to make more welding videos.

Some things that I have learned:

Don't use pure tungsten electrodes. The new rare-earth blends work very well on nearly all metals.

Sharpen the electrode to a very fine point for low-current welding, and sharpen it like a pencil for higher (eg over 100A) welding.

Keep the electrode balance control electrode negative ("weld") and only shift toward electrode positive ("clean") when absolutely necessary.

The welder's pulse feature turned out to be not as useful as I originally thought. It just seems to complicate things. It's definitely possible to make great welds without it.

Use fat electrodes. Some people claim that using an electrode that is "too large" for the weld current will cause the arc to wander. Nope. Just grind it to a sharp point. Thin electrodes 1/16" and .040" overheat much too easily, and provide no apparent benefit. .040" electrodes are very frustrating.

Use thin filler rod. It's much easier to feed thin rod quickly than feed fat rod slowly. As I mentioned in the video, it's easier to sneak a thin filler rod into the puddle while keeping the torch close to the surface.

Effect of long-term high pressure CO2 on acrylic

I left my supercritical CO2 chamber charged up with 750 psi liquid CO2 (not supercritical) for about a week. I then depressurized the chamber, and opened it. At first, the acrylic seemed fine with just minor surface crazing. After a few hours, I was surprised to find the acrylic had deformed in a major way and was full of CO2 bubbles. Weird!

Supercritical CO2 caffeine extraction (negative result -- more work needed)

I tried to extract caffeine from green coffee beans using supercritical CO2, but I had no success. The beans underwent a strange transformation, becoming white and rubbery after 6 hours at 80*C in supercritical CO2. I also used water and ethanol as a cosolvent, thinking that the caffeine would end up in solution in the water/ethanol mix after the CO2 became subcritical.

Do you have any advice about how this process is supposed to work?

Argon beer, an alternative to the usual CO2 carbonation

Most beer is carbonated with 100% CO2. Some beers, notably Guinness and some other porter/stouts, contain a mixture of nitrogen and CO2 in a ratio commonly 75/25 N2/CO2. The nitrogen is less soluble in water, and allows the beer to be served at a higher pressure without dissolving too much gas into the beer itself. The higher serving pressure churns up the beer as it exits the spout, and creates a creamy head that is the signature of a good Guinness pour. Some pubs use 75/25 gas to push normally carbonated beers out of the tap, but the beers themselves contain only CO2.

In this video I wondered what would happen if I used argon instead of nitrogen. I started by using %100 argon since the solubility of Ar is between that of N2 and CO2. As it turns out, the Ar is not soluble enough to produce a decent head on the beer. Additionally, the complete lack of CO2 makes the beer taste sweet (like it's flat) since the CO2 is necessary to form carbonic acid in water, and this is an important flavor component of beer.

Xenon has anesthetic properties at atmospheric pressure, while the other noble gasses can become anesthetic at higher pressures. Does anyone want to explore xenon beer, or have any experience with xenon used as an anesthetic?