Fighting Machine Tool Chatter with a 555 Timer

Vibration is a fact of life in almost every machining operation. Whether you’re milling, drilling, turning, or grinding, vibration can result in chatter that can ruin a part. Fighting chatter has generally been a matter of adding more mass to the machine, but if you’re clever about things, chatter reduction can be accomplished electronically, too. (YouTube, embedded below.)

When you know a little something about resonance, machine vibration and chatter start to make sense. [AvE] spends quite a bit of time explaining and demonstrating resonance in the video — fair warning about his usual salty shop language. His goal with the demo is to show that chatter comes from continued excitation of a flexible beam, which in this case is a piece of stock in the lathe chuck with no tailstock support. The idea is that by rapidly varying the speed of the lathe slightly, the system never spends very long at the resonant frequency. His method relies on a variable-frequency drive (VFD) with programmable IO pins. A simple 555 timer board drives a relay to toggle the IO pins on and off, cycling the VFD up and down by a couple of hertz. The resulting 100 RPM change in spindle speed as the timer cycles reduces the amount of time spent at the resonant frequency. The results don’t look too bad — not perfect, but a definite improvement.

It’s an interesting technique to keep in mind, and a big step up from the usual technique of more mass.

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Hackaday Links: May 21, 2017

It’s time to talk about something of supreme importance to all Hackaday readers. The first trailer for the new Star Trek series is out. Some initial thoughts: the production values are through the roof, and some of this was filmed in Jordan (thank the king for that). The writers have thrown in some obvious references to classic Trek in this trailer (taking a spacesuit into a gigantic alien thing a la TMP). There are a few new species, even though this is set about 10 years before waaaait a second, those are the Klingons?

In other news, [Seth MacFarlane] is doing a thing that looks like a Galaxy Quest series. We can only hope it’s half as good as a Galaxy Quest series could be.

The Dayton Hamvention should have been this week, but it’s never going to happen again. The Hara Arena, the traditional venue for the biggest amateur radio meet on the continent (thankfully) closed this year. Last year it was looking old and tired. This year, Hamvention moved to Xenia, Ohio, and it looks like we’re still getting the best ham swap meet on the planet. Remember: if you  drove out to Hamvention, the Air Force museum is well worth the visit. This year they have the fourth hangar open, full of space craft goodness.

Last week we saw an Open Source firmware for hoverboards, electric unicycles, and other explodey bits of self-balancing transportation. [Casainho], the brains behind this outfit, recently received an eBike controller from China. As you would expect, it’s based on the same hardware as these hoverboards and unicycles. That means there’s now Open Source firmware for eBikes.

Last year, [Cisco] built a cute little walking robot. Now it’s up on Kickstarter.

This week saw the announcement of the Monoprice Mini Delta, the much-anticipated 3D printer that will sell for less than $200. For one reason or another, I was cruising eBay this week and came upon this. They say yesterday’s trash is tomorrow’s collectors’ item, you know…

A new Tek scope will be announced in the coming weeks. What are the cool bits? It has a big touchscreen. That’s about all we know.

The ESP32 is the next great wonderchip, and has been for a while now. The ESP32 also has a CAN peripheral stuffed in there somewhere, and that means WiFi and Bluetooth-enabled cars. [Thomas] has been working on getting a driver up and running. There’s a thread on the ESP32 forum, a Hackaday.io page, and a GitHub page.

What do you do when you have a nice old Vacuum Fluorescent Display and want to show some stats from your computer? You build a thing that looks like it’s taken from a cash register. This is a project from [Micah Scott], and it has everything: electronics 3D modeling, magnets, print smoothing, creating snap-fit parts, and beautiful old displays.

Here’s something that randomly showed up in our Tip Line. [Mark] recently found some unused HP 5082-7000 segment displays in a collection of electronic components (pics below). According to some relevant literature, these were the first LED display package available, ever.  They were released in 1969, they’re BCD, and were obviously very expensive. [Mark] is wondering how many of these were actually produced, and we’re all interested in the actual value of these things. If anyone knows if these are just prototypes, or if they went into production (and what they were used for), leave a note in the comments.

CNC Machine Boasts Big Bed, Impressive Power from Off-the-Shelf Parts

A lot of homebrew CNC machines end up being glorified plotters with a router attached that are good for little more than milling soft materials like wood and plastic. So if you have a burning need to mill harder materials like aluminum and mild steel quickly and quietly, set your sights higher and build a large bed CNC machine with off-the-shelf components.

With a budget of 2000 €, [SörenS7] was not as constrained as a lot of the lower end CNC builds we’ve seen, which almost always rely on 3D-printed parts or even materials sourced from the trash can. And while we certainly applaud every CNC build, this one shows that affordable and easily sourced mechatronics can result in a bolt-up build of considerable capability. [SörenS7]’s BOM for this machine is 100% catalog shopping, from the aluminum extrusion bed and gantry to the linear bearings and recirculating-ball lead screws. The working area is a generous 900 x 400 x 120mm, the steppers are beefy NEMA23s, and the spindle is a 3-kW VFD unit for plenty of power. The video below shows the machine’s impressive performance dry cutting aluminum.

All told, [SörenS7] came in 500 € under budget, which is a tempting price point for a machine this big and capable.

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Now is the Golden Age of Artisanal, Non-Traditional Tube Amps

Earlier in the month, [Elliot Williams] quipped that it had been far too long since we saw a VFD-based amplifier build. Well, that dry spell is over. This week, [kodera2t] started showing off his design for a VFD headphone amp.

Here’s the thing, this isn’t using old surplus vacuum fluorescent displays. This is actually a new part. We first covered it about 18 months ago when Korg and Noritake announced the NuTube. It’s the VFD form factor you would find in old stereo and lab equipment, but housed in the familiar glass case is a triode specifically designed for that purpose.

Check out [kodera2t’s] video below where he walks through the schematic for his amplifier. Since making that video he has populated the boards and taken it for a spin — no video of that yet but we’re going to keep a watchful eye for a follow-up. Since these parts can be reliably sourced he’s even planning to sell it in his Tindie store. If you want to play around with this new tube that’s a pretty easy way to get the tube and support hardware all in one shot. This is not a hack, it’s being used for exactly what Korg and Noritake designed it to do, but we hope to see a few of these kits hacked for specific tastes in amp design. If you do that (or any other VFD hacking) we want to hear about it!

And now for the litany of non-traditional VFD amps we’ve grown to love. There is the Nixie amp where [Elliot] made the quip I mentioned above, here’s an old radio VFD amp project, in this one a VCR was the donor, and this from wayback that gives a great background on how this all works.

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“Nixie” Tubes Sound Good

A tube is a tube is a tube. If one side emits electrons, another collects them, and a further terminal can block them, you just know that someone’s going to use it as an amplifier. And so when [Asa] had a bunch of odd Russian Numitron tubes on hand, an amplifier was pretty much a foregone conclusion.

A Numitron is a “low-voltage Nixie”, or more correctly a single-digit VFD in a Nixiesque form factor. So you could quibble that there’s nothing new here. But if you dig into the PDF writeup, you’ll find that the tubes have been very nicely characterised, situating this project halfway between dirty hack and quality lab work.

It’s been a while since we’ve run a VFD-based amplifier project, but it’s by no means the first time. Indeed, we seem to run one every couple years. For instance, here is a writeup from 2010, and the next in 2013. Extrapolating forward, you’re going to have to wait until 2019 before you see this topic again.

VFD Clock Only Speaks Romanian

There’s no shortage of clock projects, but [niq_ro] has his own take using a vacuum fluorescent display (VFD), and Arduino, and a pair of MAX6921 ICs. Those chips are made to drive a VFD, and the use of two of the ICs required a bit of work. The Arduino is not a great time keeper, so the clock also uses a DS3231 clock module and a humidity and temperature sensor.

The clock is in Romanian, although there are some options for different text. You can find the code on GitHub and can see the result in the video below.

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[Sprite_tm] Gives Near Death VFD a Better Second Life

[Sprite_tm] picked up some used VFD displays for cheap, and wanted to make his own custom temperature and air-quality display. He did that, of course, but turned it into a colossal experiment in re-design to boot. What started out as a $6 used VFD becomes priceless with the addition of hours of high-powered hacking mojo.

You see, the phosphor screen had burnt-in spots where the old display was left static for too long. A normal person would either live with it or buy new displays. [Sprite_tm] ripped off the old display driver and drives the row and column shift registers using the DMA module on a Raspberry Pi2, coding up his own fast PWM/BCM hybrid scheme that can do greyscale.

He mapped out the individual pixels using a camera and post processing in The Gimp to establish the degradation of burnt-in pixels. He then re-wrote a previous custom driver project to compensate for the pixels’ inherent brightness in firmware. After all that work, he wrapped the whole thing up in a nice wooden frame.

There’s a lot to read, so just go hit up his website. High points include the shift-register-based driver transplant, the bit-angle modulation that was needed to get the necessary bit-depth for the grayscale, and the PHP script that does the photograph-based brightness correction.

Picking a favorite [Sprite_tm] hack is like picking a favorite ice-cream flavor: they’re all good. But his investigation into hard-drive controller chips still makes our head spin just a little bit. If you missed his talks about the Tamagotchi Singularity from the Hackaday SuperCon make sure you drop what you’re doing and watch it now.