Mechanical Logic Gates With Amplification

September 20, 2024 by Bryan Cockfield 5 Comments

One of the hardest things about studying electricity, and by extension electronics, is that you generally can’t touch or see anything directly, and if you can you’re generally having a pretty bad day. For teaching something that’s almost always invisible, educators have come up with a number of analogies for helping students understand the inner workings of this mysterious phenomenon like the water analogy or mechanical analogs to electronic circuits. One of [Thomas]’s problems with most of these devices, though, is that they don’t have any amplification or “fan-out” capability like a real electronic circuit would. He’s solved that with a unique mechanical amplifier.

Digital logic circuits generally have input power and ground connections in addition to their logic connection points, so [Thomas]’s main breakthrough here is that the mechanical equivalent should as well. His uses a motor driving a shaft with a set of pulleys, each of which has a fixed string wrapped around the pulley. That string is attached to a second string which is controlled by an input. When the input is moved the string on the pulley moves as well but the pulley adds a considerable amount of power to to the output which can eventually be used to drive a much larger number of inputs. In electronics, the ability to drive a certain number of inputs from a single output is called “fan-out” and this device has an equivalent fan-out of around 10, meaning each output can drive ten inputs.

[Thomas] calls his invention capstan lever logic, presumably named after a type of winch used on sailing vessels. In this case, the capstan is the driven pulley system. The linked video shows him creating a number of equivalent circuits starting with an inverter and working his way up to a half adder and an RS flip-flop. While the amplifier pulley does take a minute to wrap one’s mind around, it really helps make the equivalent electronic circuit more intuitive. We’ve seen similar builds before as well which use pulleys to demonstrate electronic circuits, but in a slightly different manner than this build does.

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Hackaday Links: August 25, 2024

August 25, 2024 by Dan Maloney 8 Comments

The Sun has been remarkably active lately, so much so that it might have set a new sunspot record. According to the sun watchers at the Space Weather Prediction Center, on August 8, the Solar Dynamics Observatory snapped a picture that was positively bedazzled with sunspots. Counting methods vary, but one count put the sunspot number at a whopping 337 that day. That would be the largest number since 2001, during the peak of Solar Cycle 23. The sunspot number is highly correlated with solar storms and coronal mass ejections; more spots mean more magnetic activity and more chance for something to go very, very wrong. We’ve been pretty lucky so far with Solar Cycle 25; despite being much more active than the relatively lazy Cycle 24 and much stronger than predicted, most of this cycle’s outbursts have been directed away from Earth or only dealt us a glancing blow. Seeing all those spots, though, makes us think it’s only a matter of time before we get hit with something that does more than make pretty lights.

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8-Tracks Are Back? They Are In My House

June 10, 2024 by Kristina Panos 55 Comments

What was the worst thing about the 70s? Some might say the oil crisis, inflation, or even disco. Others might tell you it was 8-track tapes, no matter what was on them. I’ve heard that the side of the road was littered with dead 8-tracks. But for a while, they were the only practical way to have music in the car that didn’t come from the AM/FM radio.

If you know me at all, you know that I can’t live without music. I’m always trying to expand my collection by any means necessary, and that includes any format I can play at home. Until recently, that list included vinyl, cassettes, mini-discs, and CDs. I had an 8-track player about 20 years ago — a portable Toyo that stopped working or something. Since then, I’ve wanted another one so I can collect tapes again. Only this time around, I’m trying to do it right by cleaning and restoring them instead of just shoving them in the player willy-nilly.

Update: I Found a Player

A small 8-track player and equally small speakers, plus a stack of VHS tapes. — I have since cleaned it.

A couple of weeks ago, I was at an estate sale and I found a little stereo component player and speakers. There was no receiver in sight. I tested the player with the speakers and bought them for $15 total because it was 75% off day and they were overpriced originally. While I was still at the sale, I hooked it up to the little speakers and made sure it played and changed programs.

Well, I got it home and it no longer made sound or changed programs. I thought about the play head inside and how dirty it must be, based on the smoker residue on the front plate of the player. Sure enough, I blackened a few Q-tips and it started playing sweet tunes again. This is when I figured out it wouldn’t change programs anymore.

I found I couldn’t get very far into the player, but I was able to squirt some contact cleaner into the program selector switch. After many more desperate button presses, it finally started changing programs again. Hooray!

I feel I got lucky. If you want to read about an 8-track player teardown, check out Jenny List’s awesome article. Continue reading “8-Tracks Are Back? They Are In My House” →

Gears Are Old And Busted, Capstans Are Cool

June 3, 2024 by Elliot Williams 44 Comments

Zero backlash, high “gear” reduction, high torque transparency, silent operation, and low cost. What is this miracle speed reduction technology, you ask? Well, it’s shoelaces and a bunch of 3D printed plastic, at least in [Aaed Musa]’s latest installment in his series on developing his own robot dog.

OK, the shoelaces were only used in the first proof of concept. [Aaed] shortly upgrades to steel cable, and finds out that steel fatigues and snaps after a few hours. He settles on Dyneema DM-20, a flexible yet non-stretching synthetic rope.

Before it’s all over, he got a five-bar linkage plotting with a pencil on the table and a quadriped leg jumping up and down on the table — to failure. All in all, it points to a great future, and we can’t wait to see the dog-bot that’s going to come out of this.

There’s nothing secret about using capstan drives, but we often wonder why we don’t see cable-powered robotics used more in the hacker world. [Aaed] makes the case that it pairs better with 3D printing than gears, where the surface irregularities really bind. If you want to get a jumpstart, the test fixture that he’s using is available on GitHub.

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There’s Not A Cassingle Thing Missing From This Cassette Deck Masterclass

October 26, 2021 by Kristina Panos 78 Comments

For [ke4mcl], this whole cassette craze of late is not a new discovery so much as it is a personal nostalgia machine. Since [ke4mcl] sees a lot of basic questions go unanswered, they made an incredible beginner’s guide to all things cassette deck. This concise wealth of information covers everything from terminology to operation, basic maintenance like repairing the belt and lubricating the motor, and appropriate cleaning methods for the various parts. Yep, we’re pretty sure this covers everything but the pencil winding technique, which you probably already knew about.

You don’t need a lot of tools and supplies to maintain a cassette deck or twelve (apparently they’re addictive) — mostly just head cleaning fluid, isopropyl, window cleaner, and a bunch of cotton swabs. And given this guide, you’ll enter the enclosure confidently, armed with knowledge about everything from the belts to the capstan to the head. This is valuable information, the kind of stuff your older brother wouldn’t take the time to explain to you in the 80s. But maybe he didn’t know reverse bias from the holes in the top of the tape.

Don’t care for the quality of audio cassettes? Tapes are good for lots of stuff, like data storage and decoration.

Capstan Winch Central To This All-Band Adjustable Dipole Antenna

February 23, 2021 by Dan Maloney 18 Comments

The perfect antenna is the holy grail of amateur radio. But antenna tuning is a game of inches, and since the optimum length of an antenna depends on the frequency it’s used on, the mere act of spinning the dial means that every antenna design is a compromise. Or perhaps not, if you build this infinitely adjustable capstan-winch dipole antenna.

Dipoles are generally built to resonate around the center frequency of one band, and with allocations ranging almost from “DC to daylight”, hams often end up with a forest of dipoles. [AD0MZ]’s adjustable dipole solves that problem, making the antenna usable from the 80-meter band down to 10 meters. To accomplish this feat it uses something familiar to any sailor: a capstan winch.

The feedpoint of the antenna contains a pair of 3D-printed drums, each wound with a loop of tinned 18-gauge antenna wire attached to some Dacron cord. These make up the adjustable-length elements of the antenna, which are strung through pulleys suspended in trees about 40 meters apart. Inside the feedpoint enclosure are brushes from an electric drill to connect the elements to a 1:1 balun and a stepper motor to run the winch. As the wire pays out of one spool, the Dacron cord is taken up by the other; the same thing happens on the other side of the antenna, resulting in a balanced configuration.

We think this is a really clever design that should make many a ham happy across the bands. We even see how this could be adapted to other antenna configurations, like the end-fed halfwave we recently featured in our “$50 Ham” series.

Cable Mechanism Maths: Designing Against The Capstan Equation

January 26, 2021 by Sonya Vasquez 20 Comments

I fell in love with cable driven mechanisms a few years ago and put together some of my first mechanical tentacles to celebrate. But only after playing with them did I start to understand the principles that made them work. Today I want to share one of the most important equations to keep in mind when designing any device that involves cables, the capstan equation. Let some caffeine kick in and stick with me over the next few minutes to get a sense of how it works, how it affects the overall friction in your system, and how you can put it to work for you in special cases.

A Quick Refresher: Push-Pull Cable Driven Mechanisms

But first: just what exactly are cable driven mechanisms? It turns out that this term refers to a huge class of mechanisms, so we’ll limit our scope just to push-pull cable actuation systems.

These are devices where cables are used as actuators. By sending these cables through a flexible conduit, they serve a similar function to the tendons in our body that actuate our fingers. When designing these, we generally assume that the cables are both flexible and do not stretch when put in tension. Continue reading “Cable Mechanism Maths: Designing Against The Capstan Equation” →