Circuit VR: Measuring With LTSpice

August 23, 2018 by 13 Comments

Usually, with Circuit VR we look at some circuit in detail with simulation — usually LTSpice. This one will be a little meta because I wanted to look at a capability in LTSpice which ironically is very useful, but not often used. Along the way, though, we’ll look at why you get maximum power transfer when your source impedance matches your load impedance. This is something you probably already know about, but it is interesting to look at in simulation if you know how to coax LTSpice — no pun intended — into showing you a meaningful graph.

The circuit is super simple. An AC source and a 50-ohm resistor stand-in for a 40-meter ham transmitter. With 100 volts into a 50-ohm load. So far, so good.

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Semi-automated Winder Spins Rotors For Motors

August 17, 2018 by 8 Comments

What’s your secret evil plan? Are you looking for world domination by building a machine that can truly replicate itself? Or are you just tired of winding motor rotors and other coils by hand? Either way, this automated coil winder is something you’re probably going to need.

We jest in part, but it’s true that closing the loop on self-replicating machines means being able to make things like motors. And for either brushed or brushless motors, that means turning spools of wire into coils of some sort. [Mr Innovative]’s winder uses a 3D-printed tube to spin magnet wire around a rotor core. A stepper motor turns the spinner arm a specified number of times, pausing at the end so the operator can move the wire to make room for the next loop. The rotor then spins to the next position on its own stepper motor, and the winding continues. That manual step needs attention to make this a fully automated system, and we think the tension of the wire needs to be addressed so the windings are a bit tighter. But it’s still a nice start, and it gives us some ideas for related coil-winding projects.

Of course, not every motor needs wound coils. After all, brushless PCB motors with etched coils are a thing.

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Hanging, Sliding Raspi Camera Adds Dimension To Octoprint

August 16, 2018 by 13 Comments

Are you using Octoprint yet? It’s so much more than just a way to control your printer over the internet, or to keep tabs on it over webcam when you’re off at work or fetching a beer. The 3D printing community has rallied around Octoprint, creating all sorts of handy plug-ins like Octolapse, which lets you watch the print blossom from the bed via time-lapse video.

Hackaday alum [Jeremy S Cook] wanted to devise a 3D-printable mount for a Raspi camera after finding himself inspired by [Tom Nardi]’s excellent coverage of Octoprint and Octolapse. He recently bought a wire shelving unit to store his printer and printer accessories, and set to work. We love the design he came up with, which uses the flexibility of the coolant hose to provide an endlessly configurable camera arm. But wait, there’s more! Since [Jeremy] mounted it to the rack with zip ties, the whole rig shimmies back and forth, providing a bonus axis for even more camera views. Slide past the break to see [Jeremy]’s build/demo video.

It’s great to be able to monitor a print from anywhere with internet access, but the camera is almost always set up for a tight shot on the print bed. How would you ever know if you’re about to run out of filament? For that, you need a fila-meter.

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Arcade Inspired Halloween Candy Dispenser

August 15, 2018 by 3 Comments

The days are getting shorter and the nights are a little cooler, which can only mean one thing: it’s officially time to start devising the trials you’ll put the neighborhood children through this Halloween. For [Randall Hendricks], that means building a new candy dispensing machine to make sure the kids have to work for their sugary reward. After all, where’s the challenge in just walking up and taking some candy from a bowl? These kids need to build character.

[Randall] writes in to share his early work on this year’s candy contraption which he’s based on a popular arcade game called “Goal Line Rush”. In this skill based game a disc with various prizes spins slowly inside the machine, and the player has a button that will extend an arm from the rear of the disc. The trick is getting the timing right to push the prize off the disc and into the chute. Replace the prizes with some empty calorie balls of high fructose corn syrup, and you get the idea.

There’s still plenty of time before All Hallows’ Eve, so the machine is understandably still a bit rough. He hasn’t started the enclosure yet, and at this point is still finalizing the mechanics. But this early peek looks very promising, and in the video after the break you can see how the machine doles out the goodies.

The disc is rotated by a high torque motor, and the aluminum extrusion arm is actuated with a gear motor and custom chain drive. Some 3D printed hardware, a couple limit switches, and a pair of relays make for a fairly straightforward way of pushing the rod out when the player presses the button on the front of the cabinet.

Considering how his previous Mario-themed candy dispenser came out, we doubt this new machine will fail to impress come October. The neighborhood kids should just count themselves lucky he’s not using his creativity to terrorize them instead.

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Junk Bin Spin Coater Uses Modded Case Fan

August 3, 2018 by 4 Comments

We’ve all been there: you need a specific tool or gadget to complete a project, but it’s not the kind of thing you necessarily want to fork over normal retail price for. It could be something you’re only going to use once or twice, or maybe you’re not even sure the idea is going to work and don’t want to invest too much money into it. You cast a skeptical towards the ever-growing pile of salvaged parts and wonder…

Inspiration and a dig through the junk bin is precisely how [Nixie] built this very impressive spin coater for use in his ongoing homemade semiconductor project. If you’ve never had first hand experience with a spin coater, don’t worry, not many people have. Put simply, it’s a machine that allows the user to deposit a thin layer of material on a disc by way of centrifugal force. Just place a few drops in the center of the disc, then spin it up fast enough and let physics do the rest.

[Nixie] only needs to spin up a fairly tiny disc, and realized the hub of a 40x40mm brushless case fan was just about the perfect size. A quick pass through the lathe stripped the hub of its blades and faced off the front. Once he found a tube that was the exact same diameter of the fan’s axle, he realized he could even use a small vacuum pump to hold his disc in place. A proper seal is provided by 10 and 16 mm OD o-rings, installed into concentric grooves he machined into the face of the hub.

With a way to draw a vacuum through the hub of the spinner he just needed the pump. As luck would have it, he didn’t have to wait for one to make the journey from China, as he had one of those kicking around his junk bin from a previous project. The only thing he ended up having to buy was the cheap PWM fan controller which he mounted along with the modified fan to a piece of black acrylic; producing a fairly professional looking little piece of lab equipment. Check out the video after the break for a brief demonstration of it in action.

This isn’t the first specialized piece of gear [Nixie] has produced in his quest for DIY chips. We’ve previously covered his DIY tube oven as well as his vacuum chamber complete with magnetically controlled manipulator arm.

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Old LED Light Bulbs Give Up Filaments For Spider Web Clock

August 1, 2018 by 41 Comments

We love it when something common gets put to a new and unusual use, especially when it’s one of those, “Why didn’t I think of that?” situations. This digital clock with a suspended display is just such a thing.

The common items in this case were “filaments” from LED light bulbs, those meant to mimic the look of clear-glass incandescent light bulbs. [Andypugh] had been looking at them with interest for a while, and realized they were perfect as the segments for a large digital clock. The frame of the clock was formed from bent brass U-channel and mounted to an oak base via turned stanchions. The seven-segment displays were laid out in the frame and the common anodes of the LED filaments were connected together, with the cathode for each connected to a very fine wire. Each wire was directed through a random hole in the frame and channeled down into the base, to be hooked to one of the four DS8880 VFD driver chips. The anode wires form a lacy filigree behind the segments, which catch the light and make then look a little like a spider’s web. It looks great, but nicht für der gefingerpoken – the frame is at 80 VDC to drive the LED segments. The clock is synced to the UK atomic clock with a 60-kHz radio link; see the long, painful sync process in the video below.

We like the open frame look, which we’ve seen before with an equally dangerous sculptural nixie clock. And this gives us some ideas for what to do with those filament LEDs other than turning them back into a light bulb. And if [Andy] sounds familiar, it could be because he’s appeared here before. First of all resurrecting the parts bin for an entire classic motorcycle marque, and then as the designer of SMIDSY, a robot competitor in the first incarnation of the UK Robot Wars series.

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