Repairing Crystal Earpieces

If you make crystal radios, you’ve probably got a few crystal earpieces. The name similarity is a bit coincidental. The crystal in a crystal radio was a rectifier (most often, these days, a germanium diode, which is, a type of crystal). The crystal in a crystal earpiece is a piezoelectric sound transducer.

Back in the 1960s, these were fairly common in cheap transistor radios and hearing aids. Their sound fidelity isn’t very good, but they are very sensitive and have a fairly high impedance, and that’s why they are good for crystal radios.

[Steve1001] had a few of these inexpensive earpieces that either didn’t work or had low sound output. He found the root cause was usually a simple problem and shares how to fix them without much trouble.

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Everyone Should Build At Least One Regenerative Radio Receiver

When we build an electronic project in 2016, the chances are that the active components will be integrated circuits containing an extremely large amount of functionality in a small space. Where once we might have used an op-amp or two, a 555 timer, or a logic gate, it’s ever more common to use a microcontroller or even an IC that though it presents an analog face to the world does all its internal work in the digital domain.

Making A Transistor Radio, 2nd edition cover. Fair use, via Internet Archive.
Making A Transistor Radio, 2nd edition cover. Fair use, via Internet Archive.

There was a time when active components such as tubes or transistors were likely to be significantly expensive, and integrated circuits, if they even existed, were out of the reach of most constructors. In those days people still used electronics to do a lot of the same jobs we do today, but they relied on extremely clever circuitry rather than the brute force of a do-anything super-component. It was not uncommon to see circuits with only a few transistors or tubes that exploited all the capabilities of the devices to deliver something well beyond that which you might expect.

One of the first electronic projects I worked on was just such a circuit. It came courtesy of a children’s book, one of the Ladybird series that will be familiar to British people of a Certain Age: [George Dobbs, G3RJV]’s Making A Transistor Radio. This book built the reader up through a series of steps to a fully-functional 3-transistor Medium Wave (AM) radio with a small loudspeaker.

Two of the transistors formed the project’s audio amplifier, leaving the radio part to just one device. How on earth could a single transistor form the heart of a radio receiver with enough sensitivity and selectivity to be useful, you ask? The answer lies in an extremely clever circuit: the regenerative detector. A small amount of positive feedback is applied to an amplifier that has a tuned circuit in its path, and the effect is to both increase its gain and narrow its bandwidth. It’s still not the highest performance receiver in the world, but it’s astoundingly simple and in the early years of the 20th century it offered a huge improvement over the much simpler tuned radio frequency (TRF) receivers that were the order of the day.

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Recapture Radio’s Roots with an Updated Regenerative Receiver

Crystal radios used to be the “gateway drug” into hobby electronics. Trouble was, there’s only so much one can hope to accomplish with a wire-wrapped oatmeal carton, a safety-pin, and a razor blade. Adding a few components and exploring the regenerative circuit can prove to be a little more engaging, and that’s where this simple breadboard regen radio comes in.

Sometimes it’s the simple concepts that can capture the imagination, and revisiting the classics is a great way to do it. Basically a reiteration of [Armstrong]’s original 1912 regenerative design, [VonAcht] uses silicon where glass was used, but the principle is the same. A little of the amplified RF signal is fed back into the tuned circuit through an additional coil on the ferrite rod that acts as the receiver’s antenna. Positive feedback amplifies the RF even more, a germanium diode envelope detector demodulates the signal, and the audio is passed to a simple op amp stage for driving a headphone.

Amenable to solderless breadboarding, or even literal breadboard construction using dead bug or Manhattan wiring, the circuit invites experimentation and looks like fun to fiddle with. And getting a handle on analog and RF concepts is always a treat.

[via r/electronics]

A Bold Experiment In A Decentralised Low Voltage Local DC Power Grid

January, for many of us in the Northern Hemisphere, can be a depressing month. It’s cold or wet depending where you live, the days are still a bit short, and the summer still seems an awfully long way away. You console yourself by booking a ticket to a hacker camp, but the seven months or so you’ll have to wait seems interminable.

If you want an interesting project to look forward to, take a look at [Benadski]’s idea for a decentralised low voltage local DC power grid for the upcoming SHA 2017 hacker camp in the Netherlands. The idea is to create a network that is both safe and open for hacking, allowing those with an interest in personal power generation to both have an available low-voltage power source and share their surplus power with other attendees.

The voltage is quoted as being 42V DC +/- 15%, which keeps it safely under the 50V limit set by the European Low Voltage Directive. Individuals can request a single 4A connection to the system, and villages can have a pair of 16A connections, which should supply enough for most needs. Users will need to provide their own inverters to connect their 5V or 12V appliances, fortunately a market served by numerous modules from your favourite Far Eastern sales portal.

This project will never be the solution to all power distribution needs, but to be fair that is probably not the intention. It does however provide a platform for experimentation, collaboration, and data gathering for those interested in the field, and since it is intended to make an appearance at future hacker camps there should be the opportunity for all that built up expertise to make it better over time.

We’ve touched on this subject before here at Hackaday, with our look at the availability of standard low voltage DC domestic connectors.

Wind turbine image: Glogger (CC BY-SA 3.0) via Wikimedia Commons.

CES2017: Astrophotography In The Eyepiece

If you’ve never set up a telescope in your back yard, you’ve never been truly disappointed. The Hubble can take some great shots of Saturn, nebulae, and other astronomical phenomena, but even an expensive backyard scope produces only smudges. To do astronomy properly, you’ll spend your time huddled over a camera and a computer, stacking images to produce something that almost lives up to your expectations.

At CES, Unistellar introduced a device designed to fit over the eyepiece of a telescope to do all of this for you.

According to the guys at Unistellar, this box contains a small Linux computer, camera, GPS, and an LCD. Once the telescope is set up, the module takes a few pictures of the telescope’s field of view, stacks the images, and overlays the result in the eyepiece. Think of this as ‘live’ astrophotography.

In addition to making Jupiter look less like a Great Red Smudge, the Unistellar module adds augmented reality; it knows where the telescope is pointing and will add a label if you’re looking at any astronomical objects of note.

While I wasn’t able to take a look inside this extremely cool device, the Unistellar guys said they’ll be launching a crowdfunding campaign in the near future.

Hackaday Links: December 25th, 2016

You should be watching the Doctor Who Christmas special right now. Does anyone know when the Resturant at the End of the Universe spinoff is airing?

We have a contest going on right now. It’s the 1 kB Challenge, a contest that challenges you to do the most with a kilobyte of machine code. The deadline is January 5th, so get cracking.

A few years ago, [Kwabena] created the OpenMV, a Python-powered machine vision module that doesn’t require a separate computer. It’s awesome, and we’re going to have his talk from the Hackaday SuperConference up shortly. Now the OpenMV is getting an upgrade. The upgrades include an ARM Cortex M7, more RAM, more heap for less money. Here’s a link to preorder.

There ain’t no demoscene party like an Amtrak demoscene party because an Amtrak demoscene party lasts ten hours.

E-paper displays are fancy, cool, and low-power. Putting them in a project, however, is difficult. You need to acquire these display modules, and this has usually been a pain. Now Eink has a web shop where you can peruse and purchase epaper display modules and drivers.

[Kris] built a pair of STM32L4 dev boards that are easily programmed in the Arduino IDE. Now he’s putting these boards up on Kickstarter. The prices are reasonable – $15 for the smaller of the pair, and $25 for the bigger one. Remember, kids: ARM is the future, at least until RISC-V takes over.

This is how you do holiday greeting cards.

Didn’t get what you want for Christmas?  Don’t worry, Amazon still has A Million Random Digits with 100,000 Normal Deviates in stock. It’s also available on audible dot com. Sometimes we don’t have time to sit down and read a million random digits but with audible dot com, you can listen to a million random digits in audio book format. That’s audible dot com please give us money.

northkoreaThis is the last Hackaday Links post of the year, which means it’s time for one of our most cherished traditions: reviewing our readership in North Korea.

It’s been a banner year for Hackaday in the Democratic People’s Republic of North Korea. The readership has exploded in 2016, with a gain of nearly 300%. To put that in perspective, in 2015 we had thirty-six views from North Korea across every page on Hackaday. In 2016, that number increased to one hundred and forty.

That’s a phenomenal increase and a yearly growth that is unheard of in the publishing industry. We’d like to tip our hat to all our North Korean reader, and we’re looking forward to serving you in 2017.

Hackaday Links: December 18, 2016

You can fly a brick if it has offset mass and you can fly a microwave because it breaks the law of the conservation of momentum. A paper on the EM Drive was recently published by the Eagleworks team, and the results basically say, ‘if this works, it’s a terrible thruster that shouldn’t work’. Experts have weighed in, but now we might not have to wait for another test in the Eagleworks lab: China will fly an EM Drive on their space station. Will it work? Who knows.

The ESP32 is just now landing on workbenches around the globe, and already a few people are diving into promiscuous mode and WiFi packet injection.

The Large Hadron Collider is the most advanced piece of scientific apparatus ever built. It produces tons of data, and classifying this data is a challenge. The best pattern recognition unit is between your ears, so CERN is crowdsourcing the categorization of LHC data.

Holy crap this is cyberpunk. [SexyCyborg] created a makeup palette pen testing device thing out of a Rasberry Pi and a few bits and bobs sitting around in a parts drawer. The project is cool, but the photolog of the finished project is awesome. It’s exactly what you would use to break into the Weyland-Yutani database while evading government operatives on the rooftops of Kowloon Walled City before escaping via grappling hook shot into the belly of a spaceplane taking off.

The Mini NES is Nintendo’s most successful hardware offering since the N64. This tiny device, importantly packaged in a minified retro NES enclosure, is out of stock everywhere. That doesn’t matter because now there’s a mini Genesis. The cool kids had a Genesis. You want to be a cool kid, right? Mortal Kombat was better on the Genesis.

The Arduino (what once was two is again one) launched a new vowel-hating model: MKRZero. The narrow board is powered by USB or LiPo, centers around an Atmel SAMD21 Cortex-M0+ chip, and sports both an I2C breakout header and a microSD card slot. Just watch those levels as these pins are not 5v tolerant.

The American Association for the Advancement of Science is holding a Scientific Maker Exhibit during its annual meeting. This type of exhibit isn’t a poster or presentation — it’s just some table space and a chance to show off a 3D printed apparatus, a new type of sensor, equipment, or some other physical thing. Details in this PDF. This is actually cooler than it sounds, and a significant departure from the traditional poster or presentation found at every other scientific conference.

Did you know Hackaday has a retro edition made specifically for old computers connected to the Internet? That’s my baby, and it’s time for a refresh. If you have any feature requests you’d like to see, leave a note in the comments.