Category: Random Projects
Random projects that I do to improve my life, try out an interesting new technology, learn a new skill, etc.
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One of the greatest advantages of AC power over DC is the ability to change its voltage by way of a transformer. However, transformers are bulky and expensive, especially variable transformers that allow household AC voltage to be lowered to throttle various electronic devices. But you can cheat: instead of varying the voltage, you can switch the power on and off to “chop off” part of each AC half-wave, effectively varying the voltage (though the output is not perfectly sinusoidal), with results that are good enough for many applications. Theory I found this very helpful article describing most of the…
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Sand-cast parts commonly have internal geometries (ex. holes) that are produced with cores, internal molds made of bonded sand that are inserted into the main mold. The Theory I found an excellent book of practical sand casting information in the 1958 US Navy Foundry Manual. Cores are usually only supported by the mold at a few points, so they must be quite strong to withstand their own weight, as well as the buoyant forces produced when they are submerged in molten metal. For this reason they are made of a bonded sand different from normal molding sand. Typically, oil is…
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I picked up a broken blender from a neighbor, hoping to fix it and use it for my own projects. The blender is powered by a 1500 W universal motor, whose speed is controlled by a TRIAC. A safety switch prevents the motor from running, even if it receives power from the mainboard, unless a blender bowl is put on with its lid in place. It also shorts out the motor when the bowl is removed, possibly as a safety feature to brake the motor if the bowl is suddenly removed rather than let it coast to a stop. A…
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In a recent science fair project, I used a drill press as a press for strength testing. Drill presses are designed to exert fairly high forces while keeping the spindle perfectly straight. Pretty much all drill presses also have some provision to measure downwards travel, allowing the measurement of strain. Additionally, the self-holding Jacobs taper used to mount chucks can be used to mount 3D-printed test fixtures. This all makes drill presses a good choice for a DIY compressive or flexural strength-testing machine that you may already have at home. Unfortunately, since the Jacobs taper will release if you …
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In this blog post, I detailed several ways of using backyard clay. The method that produced the best results was levigation, in which clay was suspended in water while impurities floated to the top or settled out. The clay-water was poured off and allowed to settle for a long time, after which the water was poured off from the settled clay. My mistake was severely underestimating the amount of clay that can be suspended in water. I initially thought that it worked something like the dissolution of ionic compounds, where clay particles go into suspension until the water can hold…
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Introduction I’m trying to get better at casting, and this involves building a proper furnace to melt metals like aluminium and copper instead of just ones that can melt on a stovetop, like zinc. This mainly involves two things: the furnace’s body, and a burner. There are a few different types of burners that are used by hobbyists, and the most common are solid fuel, propane, and oil. Solid fuel furnaces are very easy to make, but don’t get very hot and are expensive to run. Propane burners are a bit harder to make, less expensive to run, and get…
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I know I’m definitely not the first person to think of this, but I tried it yesterday and it works so well: using PVA glue (Elmer’s glue-all) to stiffen fabric. The back-story is this: I finally needed a proper wallet, so I made one myself using some denim from old jeans. Unfortunately, it was way too floppy and the large pocket in the back for putting dollar bills was so loose it would let the bills fall out really easily. As a last-ditch effort to fix it before just buying a proper wallet, I decided to try mixing some glue…
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A problem that I’ve had is that I keep forgetting to close the garage door at night, which lets in the elements (and also rats). After being pestered for some time by my parents to find a solution, I finally came up with this. The solution is to turn on the overhead lights any time the garage door is open at night. Since the garage is in plain view of my house, this makes it really obvious when the door is open. Unlike something that automatically closes the door, a solution like this doesn’t need control of the garage door…
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Part of my bicycle-lighting project involved crimping a splitter cable to split the output of the dynamo to the front and rear lamps. I used a DuPont connector for that because I had recently bought, after 4 years of consideration, a proper DuPont crimper. The input and output wires were 24 AWG solid wires with an insulation diameter of about 1.3 mm. A DuPont crimp actually consists of 2 crimps, one onto the stripped wire, and another onto the insulation for strain relief. The biggest challenge when attempting to crimp 2 wires is getting the insulation of both properly into…
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Recently finding the need to bike home in the dark, and not wanting to regularly charge a battery-powered light, I decided to buy a used bicycle dynamo (for $40) to power a front and rear bike light. The dynamo is a bottom-bracket dynamo, which means it’s meant to be mounted on the bottom bracket (where the pedals are mounted) and is driven by the tire tread. This contrasts with bottle dynamos which are driven by the sidewall of the tire, potentially wearing out the sidewall. There was no space to mount the dynamo on my bottom bracket, but thankfully it…
