Tag Archives: hardware

Retrotechtacular: Synchros Go to War (and Peace)

via hardware – Hackaday

Rotation. Motors rotate. Potentiometers and variable capacitors often rotate. It is a common task to have to rotate something remotely or measure the rotation of something. If I asked you today to rotate a volume control remotely, for example, you might offer up an open loop stepper motor or an RC-style servo. If you wanted to measure a rotation, you’d likely use some sort of optical or mechanical encoder. However, there’s a much older way to do those same tasks and one that still sees use in some equipment: a synchro.

The synchro dates back to the early 1900s when the Panama Canal used them to read and control valves and gates. These devices were very common in World War II equipment, too. In particular, they were often part of the mechanisms that set and read gun azimuth and elevation or — like the picture to the left — a position indication of a radar antenna. Even movie cameras used these devices for many years. Today, with more options, you don’t see them as much except in applications where their simplicity and ruggedness is necessary.

How Do They Work?

A synchro looks like a motor, but it is really a transformer optimized for specific applications. For example, it is common to see a synchro transmitter and a synchro receiver, although usually the devices can work as both. When wired together and excited with the proper AC voltage, turning one synchro shaft will turn the other the same amount. And one transmitter can drive multiple receivers. For example, an airplane cockpit may have an instrument that uses one transmitter and has two receivers, one for the pilot and another for the copilot.

A basic synchro is similar to a motor in that it has a rotor and a stator. However, each of these has a transformer winding. Some devices use single phase and others use three-phase. In addition, devices made for vehicles probably use 400 Hz AC instead of the 50 or 60 Hz common for stationary units. Usually, light-duty units made to drive indicators use single phase but synchros that transmit torque will use three-phase connections.

You can consider a synchro as a variable-coupling transformer. Rotating the shaft varies the magnitude of the magnetic coupling between the primary and secondary. That means the output voltage varies based on the shaft position. If you wire two synchros together, the circuit acts like a bridge. When the two devices are in the same position, the system is in balance — that is, putting out equal and opposing voltages. But if one shaft moves, the imbalance causes current to flow through the windings moving the other shaft to equilibrium. This configuration is sometimes known by the old General Electric name Selsyn. Other trade names included Teletorque and Autosyn, but you don’t hear those as often.

Variety and Power

There are many variations. Some synchros have brushes and others are brushless. Some are made for precision. In high precision applications, you may have a coarse transmitter slaved to a fine transmitter that rotates multiple times for each full rotation of the coarse shaft for reading a more precise value. You can think of this like a clock, where the big hand goes around twelve times for each rotation of the little hand. Usually, the gearing ratio is 36:1 or 72:1 so that each rotation of the fine shaft corresponds to five or ten degrees of the coarse transmitter.

Making a little handle turn a giant gun mount was problematic. At first, the receiver motor just told a human what to do using an indicator and then the human operated the gun. However, the development of the amplidyne made it possible to amplify the synchro outputs to directly drive larger loads.

The Amplidyne

The amplidyne has a superficial resemblance to a dynamotor — that is, a generator turned by a motor. However, in a dynamotor, you turn the generator to make a high voltage. In an amplidyne, the motor still turns the generator, but an input voltage is put on the generator’s field winding. The more current you apply, the higher the output voltage. This creates a very low-frequency amplifier that takes a current input and produces a voltage output.

Amplidynes found use in other applications, too. Elevators, locomotives, and even nuclear submarines. Of course, today, we have much better options for doing high power amplification, but there could be a few still hiding in some old building’s elevator, somewhere.

More Info

Because these were used extensively in the Navy, one of the best sources of information is an old Navy pamphlet (if you consider 166 pages a pamphlet; if it disappears, search for OP 1303). If you want something more modern, Moog (the aerospace company, not the synthesizer company, although the companies were founded by cousins) has an application guide and a handbook you might find interesting.

You won’t find too many of these interesting devices in use today, although there are companies that make modern encoders that specifically target traditional synchro applications. Of course, tubes made a comeback. Maybe that pile of World War II surplus synchros in the secret Hackaday bunker will be worth something one day.

Speaking of World War II, check out the 1944 instructional video below about airplanes that could move guns electrically using all these components.

Photo Credits:

Synchro by MGeek CC BY-SA-3.0

First Lithographically Produced Home Made IC Announced

via hardware – Hackaday

It is now six decades since the first prototypes of practical integrated circuits were produced. We are used to other technological inventions from the 1950s having passed down the food chain to the point at which they no longer require the budget of a huge company or a national government to achieve, but somehow producing an integrated circuit has remained out of reach. It’s the preserve of the Big Boys, move on, there’s nothing to see here.

Happily for us there exists a dedicated band of experimenters keen to break that six-decade dearth of home-made ICs. And now one of them, [Sam Zeloof], has made an announcement on Twitter that he has succeeded in making a dual differential amplifier IC using a fully lithographic process in his lab. We’ve seen [Jeri Ellsworth] create transistors and integrated circuits a few years ago and he is at pains to credit her work, but her interconnects were not created lithographically, instead being created with conductive epoxy.

For now, all we have is a Twitter announcement, a promise of a write-up to come, and full details of the lead-up to this momentous event on [Sam]’s blog. He describes both UV lithography using a converted DLP projector and electron beam lithography using his electron microscope, as well as sputtering to deposit aluminium for on-chip interconnects. We’ve had an eye on his work for a while, though his progress has been impressively quick given that he only started amassing everything in 2016. We look forward to greater things from this particular garage.

Assemble Your Own Modular Li-Ion Batteries

via hardware – Hackaday

Low-voltage DC power electronics are an exciting field right now. Easy access to 18650 battery cells and an abundance of used Li-Ion cells from laptops, phones, etc. has opened the door for hackers building their own battery packs from these cheap cells. A big issue has been the actual construction of a pack that can handle your individual power needs. If you’re just assembling a pack to drive a small LED, you can probably get by with spring contacts. When you need to power an e-bike or other high power application, you need a different solution. A spot welder that costs $1000 is probably the best tool, but out of most hackers’ budget. A better solution is needed.

Vruzend v2 Battery Caps.

Enter [Micah Toll] and his Vruzend battery connectors, whose Kickstarter campaign has exceded its goal several times over. These connectors snap onto the ends of standard 18650 cells, and slot together to form a custom-sized battery pack. Threaded rods extend from each plastic cap to enable connection to a bus bar with just a single nut. The way that you connect each 18650 cell determines the battery pack’s voltage and current capability. There are a couple of versions of the connector available through the campaign, and the latest version 2.0 should allow some tremendously powerful battery pack designs. The key upgrade is that it now features corrosion-resistant, high-power nickel-plated copper busbars allowing current up to 20A continuous. A side benefit of these caps instead of welded tabs is that you can easily swap out battery cells if one fails or degrades over time.

What would you use a custom battery pack for? The Vruzen team recommends electric vehicles, e-bikes, and DIY Powerwalls. Maybe a portable 3D printer, your own laptop battery, a high-power LED flashlight, or maybe a portable Raspberry Pi cluster or two? Or you could come full circle and make a battery-powered battery welder.

[via electrek]. Thanks [Justin Monza] and [Jim Windgassen].

The Simplest Possible DIY Ultrasonic Levitator

via hardware – Hackaday

We thought that making things levitate in mid-air by the power of sound was a little bit more like magic, or at least required fancy equipment. It turns out that you can do it yourself easily enough with parts that any decent hacker’s closet should have in abundance: a motor-driver IC, two ultrasonic distance pingers, and a microcontroller. This article shows you how (translated here, scroll down).

But aside from a few clever tricks, there’s not that much to show. The two HC-SR04 ultrasonic distance sensors are standard fare, and are just being used as a cheap source of 40 kHz transducers. The circuit uses a microcontroller, but any source of 40 kHz square waves should suffice. Those of you who could do that with a 555 (or a Raspberry Pi), this one’s for you! A stepper motor driver bumps up the voltage applied to the transducers, but you could use plain-vanilla transistors as well.

It’s all the little details that count, however. You need to position the two ultrasonic drivers fairly precisely to create a standing wave, and while you can start at 8.25 mm and trial-and-error it, the article demonstrates using an oscilloscope to align the capsules by driving one and reading the signal out of the other and tweaking them until they’re in phase. Clever!

The author also takes the ultrasonic-transparent grille from one of the unused receivers and uses it as a spoon to help position the styrofoam bits in the sound waves. We always wondered how you’d do that!

It turns out that it’s easy to make a DIY ultrasonic levitation desk toy, and none of the parts are expensive or critical. The missing ingredient is just the gumption to try it, and now we have that, too.

As cool as they are, the HC-SR04 modules aren’t perfect for all distance sensing applications. Here’s everything you need to know about them, including hacks to make them work up-close. And since HC-SR04 sensors come cheapest in ten-packs, you’ll be wondering what you’re going to do with the other eight. That problem has apparently also been solved.

Computers May Someday Need A Drink

via hardware – Hackaday

“We want to put water right into your processor.” If that statement makes you sweat, that is good. Sweating is what we’re talking about, but it’s more involved than adding some water like a potted plant. Sweating works naturally by allowing liquid to evaporate, and that phase change is endothermic which is why it feels cool. Evaporative coolers that work in this way, also known as swamp coolers, haven’t been put into computers before because they are full of sloshy water. Researchers in South Korea and the United States of America have been working on an evaporative cooling system mimicking the way some insects keep themselves cool by breathing through their exoskeletons while living in damp soil.

Springtails are little bugs that have to keep the water and air separate, so they don’t drown in the wet dirt where they live. Mother Nature’s solution was for them to evolve to do this with columns that have sharp edges at the exit. Imagine you slowly add water to a test tube, it won’t spill as soon as you reach the top, it will form a dome. This is the meniscus. At a large scale, say a river dam, as soon as you get over the dam you would expect spillage, but at the test tube level you can see a curve. At the scale of the springtail, exuded water will form a globe and resist water pressure. That resistance to water pressure allows this type of water cooling to self-regulate. Those globes provide a lot of surface area, and as they evaporate, they allow more water to replenish the globe. Of course, excessive pressure will turn them into the smallest squirt guns.

We have invented a lot by copying Mother Nature. Velcro was inspired by burrs, and some of our most clever robots copy insects. We can also be jerks about it.

Motion-Controlled KVM Switch

via hardware – Hackaday

Once upon a time, [hardwarecoder] acquired a Gen8 HP microserver that he began to toy around with. It started with ‘trying out’ some visualization before spiraling off the rails and fully setting up FreeBSD with ZFS as a QEMU-KVM virtual machine. While wondering what to do next, he happened to be lamenting how he couldn’t also fit his laptop on his desk, so he built himself a slick, motion-sensing KVM switch to solve his space problem.

At its heart, this device injects DCC code via the I2C pins on his monitors’ VGA cables to swap inputs while a relay ‘replugs’ the keyboard and mouse from the server to the laptop — and vice-versa — at the same time. On the completely custom PCB are a pair of infrared diodes and a receiver that detects Jedi-like hand waves which activate the swap. It’s a little more complex than some methods, but arguably much cooler.

Using an adapter, the pcb plugs into his keyboard, and the monitor data connections and keyboard/mouse output to the laptop and server stream out from there. There is a slight potential issue with cables torquing on the PCB, but with it being so conveniently close, [hardwarecoder] doesn’t need to handle it much.

[hardwarecoder]’s post is an impressively detailed breakdown and how-to for those of you who dare to dive into a similar endeavour. When managing larger computer systems, KVM switches are convenient solution, but can be an insidious vulnerability if left unchecked.