A Few Caps For A Faster Multimeter

We just love it when someone takes apart a bench instrument. There is something about voiding a warranty and then making modifications that hits the spot and in a series of simple modifications, [Jack Zimmermann] dives into the guts if an Aneng AN8008.

The multimeter in question, the AN8008, is a low-cost true-RMS instrument that takes a bit longer to settle on the correct voltage reading than [Jack] would have liked. While poking around, he found that the DC rail inside the meter was host to noise spikes. He theorized that these were being coupled back from an element and proceeded to verify the decoupling arrangement.

The first step was to replace a Rubycon 100 uF capacitor with a Panasonic FM 100 µF which has an ESR of 0.4 Ohms, an improvement on the 1.4 Ohms of stock capacitor. Next came the addition of 0.1 µF, 1 µF and a 10 µF 0805 capacitors and finally a huge 1000 uF 10 V capacity which helped cut down the noise from 30 mV p-p to 3.6 mV p-p. And finally he added decoupling capacitors to the voltage reference chip in accordance with the manufacturer’s datasheet.

These small modifications improved the settling time as well as the stability of the measurements. [Jack] verifies the accuracy against a voltage reference and a bench meter which is good news considering the calibration certificate went out the door anyway.

This is one of the many DMM hacks we have covered in the past such as the Fluke 12E+ hack that enables hidden features though there may be other models out there with possible upgrades.

A Giant Magellan Telescope Needs Giant Mirrors

The Giant Magellan Telescope doesn’t seem so giant in the renderings, until you see how the mirrors are made.

The telescope will require seven total mirrors each 27 feet (8.4 meters) in diameter for a total combined diameter of 24.5 meters. Half of an Olympic size pool’s length. A little over four times the diameter of the James Webb Space Telescope.

According to the website, the mirrors are cast at the University of Arizona mirror lab and take four years each to make. They’re made from blocks of Japanese glass laid out in a giant oven. The whole process of casting the glass takes a year, from laying it out to the months of cooling, it’s a painstaking process.

Once the cooling is done there’s another three years of polishing to get the mirror just right. If you’ve ever had to set up a metal block for precision machining on a mill, you might have an idea of why this takes so long. Especially if you make that block a few tons of glass and the surface has to be ground to micron tolerances. A lot of clever engineering went into this, including, no joke, a custom grinding tool full of silly putty. Though, at its core it’s not much different from smaller lens making processes.

The telescope is expected to be finished in 2024, for more information on the mirror process there’s a nice article here.

Simple Jig Gives Plastic Homes to Orphaned Projects

Look around your bench and chances are pretty good that there’s a PCB or scrap of perfboard or even a breadboard sitting there, wires and LEDs sprouting off it, doing something useful and interesting. Taking it to the next level with a snazzy enclosure just seems too hard sometimes, especially if you don’t have access to a 3D printer or laser cutter. But whipping up plastic enclosures can be quick and easy with this simple acrylic bending outfit.

At its heart [Derek]’s bending rig is not much different from any of the many hot-wire foam cutters we’ve featured. A nichrome wire with a tensioning spring is stretched across a slot in a flat work surface. The slot contains an aluminum channel to reflect the heat from the wire upward and to protect the MDF bed; we wonder if perhaps an angle section set in a V-groove might not be more effective, and whether more vertical adjustment range would provide the wider heating area needed for wider radius bends. It works great as is, though, and [Derek] took the time to build a simple timer to control the heating element, for which of course he promptly built a nice looking enclosure.

We can imagine the possibilities here are endless, especially if you use colored acrylic or Lexan and add in some solvent welding. We’ve covered acrylic enclosure techniques before; here’s a post that covers the basics.

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DIY Capacitive Rotational Encoder on the Cheap with FR4

Rotary encoders are critical to many applications, even at the hobbyist level. While considering his own rotary encoding needs for upcoming projects, it occurred to [Jan Mrázek] to try making his own DIY capacitive rotary encoder. If successful, such an encoder could be cheap and very fast; it could also in part be made directly on a PCB.

First prototype, two etched plates with transparent tape as dielectric material. Disc is 15 mm in diameter.

The encoder design [Jan] settled on was to make a simple adjustable plate capacitor using PCB elements with transparent tape as the dielectric material. This was used as the timing element for a 555 timer in astable mode. A 555 in this configuration therefore generates a square wave that changes in proportion to how much the plates in the simple capacitor overlap. Turn the plate, and the square wave’s period changes in response. Response time would be fast, and a 555 and some PCB space is certainly cheap materials-wise.

The first prototype gave positive results but had a lot of problems, including noise and possibly a sensitivity to temperature and humidity. The second attempt refined the design and had much better results, with an ESP32 reliably reading 140 discrete positions at a rate of 100 kHz. It seems that there is a tradeoff between resolution and speed; lowering the rate allows more positions to be reliably detected. There are still issues, but ultimately [Jan] feels that high-speed capacitive encoders requiring little more than some PCB real estate and some 555s are probably feasible.

This project is a reminder that FR4 (whether copper-clad, etched, or blank) shows up in clever applications: copper tape and blank FR4 can be used to quickly prototype RF filters, PocketNC built an entire small CNC tool around FR4, and our own [Voja] wrote a full guide on making beautiful enclosures from FR4.

Servo-Controlled Eyeball Makes a Muggle Moody

Even when you bear a passing resemblance to the paranoid Auror of the Harry Potter universe, you still really need that wonky and wandering prosthetic eye to really sell that Mad-Eye Moody cosplay, and this one is pretty impressive.

Of course, there’s more to the [daronjay]’s prosthetic peeper than an eBay doll’s eye. There’s the micro-servo that swivels the orb, as well as a Trinket to send the PWM signal and a pocket full of batteries. The fit and finish really tie it together, though, especially considering that it’s made from, well, garbage — a metal food jar lid, a yogurt cup, and the tube of a roll-on antiperspirant. Some brass screws and a leather strap evoke the necessary Potter-verse look, and coupled with what we assume are prosthetic scars, [daronjay] really brings the character to life. We think it would be cool to have the servo eye somehow slaved to the movements of the real eye, with a little randomness thrown in to make it look good.

Marauder’s maps, wand duels, Weasley clocks — the wizarding world is ripe for creative hacking and prop making. What’s next — a Nimbus 2000 quadcopter? Please?

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Super Low Tech Mario

Browsing around the depths of the Internet we came across a super low tech version of Super Mario from [Sata Productions]. The video presents a complete tutorial on how to make a playable, cardboard version of the famous Super Mario game. If you are a fan, you probably going to like this.

You basically need cardboard, a hot glue gun, a ball bearing, a couple of DC motors, some iron BBs, some magnets, batteries, some wires… it sounds just like shopping list for a MacGuyver episode. But it works and it’s playable. It has a wired remote control, you control Mario to move and make him jump up and down in a kind of turning dashboard game. It even has a game over screen when Mario dies. Yes, Mario can die in this cardboard version. If you want to make a custom version you can always print a bigger level and resize the cardboard box.

Super Mario has had its shares of hacks, like this interface hack using a Kinect to control Mario or this super tricky jailbreak hack that allows players to run their own game mods, but this one is just on another level: a low tech approach. It seems like it could be a fun weekend project, especially if you have kids. If you’re not into Super Mario, it’s possible to just print a different game, the supporting platform is pretty generic and could support several simplified platform games.

Check out the video:

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A Sandbox for DIY Pinball Design

If you’ve always wanted to build your own pinball machine but have no idea where to start, this is the project for you. [Chris] is in the process of building a 3/4 size pinball table and is currently in the waiting-for-parts stage. As they arrive, he is testing them in a sandbox he built in an afternoon. Let [Chris]’s proving ground be your quick-start guide to all the ways you could approach the two most important parts of any pin: the flippers and targets.

The field of play is a sturdy piece of particle board, and the cardboard walls are attached with hot glue. [Chris] designed and printed a pair of flippers that are driven by some cheap remote door lock motors he found at a popular online auction house. You can see how snappy are in the test video after the break.

We love the crisp action and elegant simplicity of the spring-loaded drop targets [Chris] designed. Right now he resets them manually, but soon they will be reset by a solenoid or maybe a motor. We can’t wait to see how the table turns out. In the meantime, we’ll have to go back to drooling over this amazing life-size 3D-printed pinball machine.

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