Fail Of The Week: 3D Printed Worm Gear Drive Project Unveils Invisible Flaw

May 11, 2018 by Roger Cheng 27 Comments

All of us would love to bring our projects to life while spending less money doing so. Sometimes our bargain hunting pays off, sometimes not. Many of us would just shrug at a failure and move on, but that is not [Mark Rehorst]’s style. He tried to build a Z-axis drive for his 3D printer around an inexpensive worm gear from AliExpress. This project was doomed by a gear flaw invisible to the human eye, but he documented the experience so we could all follow along.

We’ve featured [Mark]’s projects for his ever-evolving printer before, because we love reading his well-documented upgrade adventures. He’s not shy about exploring ideas that run against 3D printer conventions, from using belts to drive the Z-axis to moving print cooling fan off the print head (with followup). And lucky for us, he’s not shy about document his failures alongside the successes.

He walks us through the project, starting from initial motivation, moving on to parts selection, and describes how he designed his gearbox parts to work around weaknesses inherent to 3D printing. After the gearbox was installed, the resulting print came out flawed. Each of the regularly spaced print bulge can be directly correlated to a single turn of the worm gear making it the prime suspect. Then, to verify this observation more rigorously, Z-axis movement was measured with an indicator and plotted against desired movement. If the problem was caused by a piece of debris or surface damage, that would create a sharp bump in the plot. The sinusoidal plot tells us the problem is more fundamental than that.

This particular worm gear provided enough lifting power to move the print bed by multiplying motor torque, but it also multiplied flaws rendering it unsuitable for precisely positioning a 3D printer’s Z-axis. [Mark] plans to revisit the idea when he could find a source for better worm gears, and when he does we’ll certainly have the chance to read what happens.

Optocouplers: Defending Your Microcontroller, MIDI, And A Hot Tip For Speed

May 9, 2018 by Elliot Williams 65 Comments

Deep in the heart of your latest project lies a little silicon brain. Much like the brain inside your own bone-plated noggin, your microcontroller needs protection from the outside world from time to time. When it comes to isolating your microcontroller’s sensitive little pins from high voltages, ground loops, or general noise, nothing beats an optocoupler. And while simple on-off control of a device through an optocoupler can be as simple as hooking up an LED, they are not perfect digital devices.

But first a step back. What is an optocoupler anyway? The prototype is an LED and a light-sensitive transistor stuck together in a lightproof case. But there are many choices for the receiver side: photodiodes, BJT phototransistors, MOSFETs, photo-triacs, photo-Darlingtons, and more.

So while implementation details vary, the crux is that your microcontroller turns on an LED, and it’s the light from that LED that activates the other side of the circuit. The only connection between the LED side and the transistor side is non-electrical — light across a small gap — and that provides the rock-solid, one-way isolation.

Continue reading “Optocouplers: Defending Your Microcontroller, MIDI, And A Hot Tip For Speed” →

Friday Hack Chat: Open Hardware For Science

May 9, 2018 by Brian Benchoff 5 Comments

Scientific equipment is expensive. It can cost hundreds of thousands of dollars to set up a lab. Simply the cost of machines, like data acquisition units or even a simple load cell, can cost hundreds of dollars. This makes research cost prohibitive, and that’s the case even if you do spend a dozen hours a week writing grant proposals. Citizen science is right out, because the cost of the tools to do science is so high.

For this week’s Hack Chat, we’re going to be talking about Open Hardware for science. This is the chat that’s all about Open Source equipment, hardware modular electronics, and Open designs to make the tools that make science.

Our guest for this week’s Hack Chat is [Dr. Alexxai Kravitz]. He has a PhD in Neuroscience from UPenn and completed a postdoc at the Gladstone Institutes in San Fransisco. [Lex]’s research focuses on understanding the reward circuitry in the brain, and his publications use a variety of experiments to examine this, including behavioral testing, in vivo electrophysiology, and optogenetics.

For this Hack Chat, we’re going to about how Open Source has made more science possible. Of note, we’ll be discussing:

What Open Source science equipment is being used today
The initiatives behind Open Source Hardware for science applications
Scientific application that could benefit from Open Hardware

You are, of course, encouraged to add your own questions to the discussion. You can do that by leaving a comment on the Hack Chat Event Page and we’ll put that in the queue for the Hack Chat discussion.

Our Hack Chats are live community events on the Hackaday.io Hack Chat group messaging. This week is just like any other, and we’ll be gathering ’round our video terminals at noon, Pacific, on Friday, May 11th. Here’s a clock counting down the time until the Hack Chat starts.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on Hackaday.io.

You don’t have to wait until Friday; join whenever you want and you can see what the community is talking about.

Sophie Wilson: ARM And How Making Things Simpler Made Them Faster & More Efficient

May 8, 2018 by Richard Baguley 84 Comments

Sophie Wilson is one of the leading lights of modern CPU design. In the 1980s, she and colleague Steve Furber designed the ARM architecture, a new approach to CPU design that made mobile computing possible. They did this by realizing that you could do more, and quicker, with less. If you’ve use a Raspberry Pi, or any of the myriad of embedded devices that run on ARM chips, you’ve enjoyed the fruits of their labor.

It all began for Sophie Wilson with an electric lighter and a slot machine (or fruit machine, as they are called in the UK) in 1978. An aspiring thief had figured out that if you sparked an electric lighter next to the machine, the resulting wideband electromagnetic pulse could trigger the payout circuit. Electronics designer Hermann Hauser had been tasked with fixing the problem, and he turned to Wilson, a student working at his company.

Wilson quickly figured that if you added a small wideband radio receiver to detect the pulse, you could suppress the false payout, foiling the thief. Impressed with this innovation, Hauser challenged Wilson to build a computer over the summer holidays, based in part on a design for an automated cow feeder that Wilson had created at university. Wilson created this prototype computer that looked more like a hand-wired calculator than a modern computer, but the design became the basis for the Acorn System 1, the first computer that Hauser’s new company Acorn Computers launched in 1979. Continue reading “Sophie Wilson: ARM And How Making Things Simpler Made Them Faster & More Efficient” →

Printed It: Toolbag Essentials

May 7, 2018 by Tom Nardi 26 Comments

While complex devices assembled from 3D printed components are certainly impressive, it’s the simple prints that have always held the most appeal to me personally. Being able to pick an object up off the bed of your printer and immediately put it to use with little to no additional work is about as close as we can get to Star Trek style replicators. It’s a great demonstration to show off the utility of your 3D printer, but more importantly, having immediate access to some of these tools and gadgets might get you out of a jam one day.

With that in mind, I thought we’d do things a little differently for this installment of Printed It. Rather than focusing on a single 3D model, we’ll be taking a look at a handful of prints which you can put to practical work immediately. I started by selecting models based on the idea that they should be useful to the average electronic hobbyist in some way or another, and relatively quick to print. Each one was then printed and evaluated to determine its real-world utility. Not all made the grade.

Each model presented here is well designed, easy to print, and most critically, legitimately useful. I can confidently say that each one has entered into my standard “bag of tricks” in some capacity, and I’m willing to bet a few will find their way into yours as well.

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Fail Of The Week: Never Assume All Crystals Are Born Equal

May 5, 2018 by Jenny List 23 Comments

You should be used to our posting the hacks that didn’t quite go according to plan under our Fail Of The Week heading, things that should have worked, but due to unexpected factors, didn’t. They are the fault, if that’s not too strong a term, of the person making whatever the project is, and we feature them not in a spirit of mockery but one of commiseration and enlightenment.

This FOTW is a little different, because it reveals itself to have nothing to do with its originator. [Grogster] was using the widely-available HC-12 serial wireless modules, or clones or even possibly fakes thereof, and found that the modules would not talk to each other. Closer inspection found that the modules with the lack of intercommunication came from different batches, and possibly different manufacturers. Their circuits and components appeared identical, so what could possibly be up?

The problem was traced to the two batches of modules having different frequencies, one being 37 kHz ahead of the other. This was in turn traced to the crystal on board the off-frequency module, the 30 MHz component providing the frequency reference for the Si4463 radio chip was significantly out of spec. The manufacturer had used a cheap source of the component, resulting in modules which would talk to each other but not to the rest of the world’s HC-12s.

If there is a lesson to be extracted from this, it is to be reminded that even when cheap components or modules look as they should, and indeed even when they appear to work as they should, there can still be unexpected ways in which they can let you down. It has given us an interesting opportunity to learn about the HC-12, with its onboard STM8 CPU and one of the always-fascinating Silicon Labs radio chips. If you want to know more about the HC-12 module, we linked to a more in-depth look at it a couple of years ago.

Thanks [Manuka] for the tip.

Ask Hackaday: Whatever Happened To Wire Wrapping?

May 4, 2018 by Dan Maloney 130 Comments

Back in the 70s when I started getting interested in electronics, tons of magazines catered to the hobbyist market. Popular Electronics was my favorite, and I think I remember the advertisements more than anything, probably because they outnumbered articles by a large margin. Looking back, it seemed like a lot of ad space was sold to companies hawking the tools and materials needed for wire wrapping, which was very popular for prototyping in the days before solderless breadboards were readily available. I remember beauty shots of neat rows of small, gold posts, with stripped wires wrapped evenly around them.

To the budding hobbyist, wire wrapping looked like the skill to have. With a huge selection of posts, terminals, and sockets for ICs and discrete components, as well as a wide range of manual and powered wrapping tools, it seemed like you could build anything with wire wrapping. But fast forward just a decade or so, and wire wrapping seemed to drop out of favor. And today — well, does anyone even wire wrap anymore?

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