Books You Should Read: Instruments Of Amplification

Psst… Wanna make a canning jar diode? A tennis ball triode? How about a semiconductor transistor? Or do you just enjoy sitting back and following along an interesting narrative of something being made, while picking up a wealth of background, tips and sparking all sorts of ideas? In my case I wanted to make a cuprous oxide semiconductor diode and that lead me to H.P. Friedrichs’ wonderful book Instruments of Amplification. It includes such a huge collection of amplifier knowledge and is a delight to read thanks to a narrative style and frequent hands-on experiments.

Friedrichs first authored another very popular book, The Voice of the Crystal, about making crystal radios, and wanted to write a second one. For those not familiar with crystal radios, they’re fun to make radios that are powered solely by the incoming radio waves; there are no batteries. But that also means the volume is low.

Readers of that book suggested a good follow-up would be one about amplifier circuits, to amplify the crystal radio’s volume. However, there were already an abundance of such books. Friedrichs realized the best follow-up would be one on how to make the amplifying components from scratch, the “instruments of amplification”.  It would be unique and in the made-from-scratch spirit of crystal radios. The book, Instruments of Amplification was born.

The Experiments

Microphonic relays
Microphonic relays, via H.P. Friedrichs Homepage

The book includes just the right amount of a history, giving background on what an amplifier is and how they first came in the electrical world. Telegraph operators wanted to send signals over greater and greater distances and the solution was to use the mix of electronics and mechanics found in the telegraph relay. This is the springboard for his first project and narrative: the microphonic relay.

The microphonic relay example shown on the right places a speaker facing a microphone; the speaker is the input with the microphone amplifying the output. He uses a carbon microphone salvaged from an old telephone headset, housing everything in an enclosure of copper pipe caps, steel bar stock, nuts and bolts mounted on an elegant looking wood base. All the projects are made with simple parts, with care, and they end up looking great.

Continue reading “Books You Should Read: Instruments Of Amplification”

Hackaday Prize Entry: Germanium Vision

The first digital cameras didn’t come out of a Kodak laboratory or from deep inside the R&D department of the CIA or National Reconnaissance Office. The digital camera first appeared in the pages of Popular Electronics in 1975, using a decapsulated DRAM module to create fuzzy grayscale images on an oscilloscope. For his Hackaday Prize project, [Alexander] is recreating this digital camera not with an easy to use decapsulated DRAM, but with individual germanium transistors.

Phototransistors are only normal transistors with a window to the semiconductor, and after finding an obscene number of old, Soviet metal can transistors, [Alex] had either a phototransistor or a terrible solar cell in a miniaturized package.

The ultimate goal of this project is to create a low resolution camera out of a matrix of these germanium transistors. [Alex] can already detect light with these transistors by watching a multimeter, and the final goal – generating an analog NTSC or PAL video signal – will “just” require a single circuit duplicated hundreds of times.

Digital cameras, even the earliest ones built out of DRAM chips, have relatively small sensors. A discrete image sensor, like the one [Alex] is building for his Hackaday Prize entry, demands a few very interesting engineering challenges. Obviously there must be some sort of lens for this image sensor, so if anyone has a large Fresnel sitting around, you might want to drop [Alex] a line.

The HackadayPrize2016 is Sponsored by:

A Rubidium Reference for Discrete Component Clocks

Sometimes you open a freshly created Hackaday.io project and discover more than you expect. A moment of idle curiosity turns into a lengthy read involving several projects you wonder how you managed to miss the first time around. So it was this morning, with [Yann Guidon]’s documentation of his eBay-purchased rubidium frequency standard. In itself an interesting write-up, with details of reverse engineering the various different internal clock signals to derive more than just the standard 1-second pulses, and touching on the thermal issues affecting frequency lock.

Transistors were EXCITING back then!
Transistors were EXCITING back then!

It is when you look at his intended use for the standard that you’ll see the reason for the lengthy read. He has a couple of discrete component clock projects on the go. His first, a low-powered MOSFET design, promises to break the mold of boring silicon bipolar transistors with hefty power consumption. It is his second, a design based on germanium transistors and associated vintage components, that really stands apart. Not a Nixie tube in sight, but do browse the project logs for a fascinating descent into the world of sourcing vintage semiconductors in 2016.

Neither clock project is finished, but both show significant progress and they’ll certainly keep time now that they’ll be locked to a rubidium standard. Take a look, and keep an eye on progress, we’re sure there will be more to come.

We’ve featured a couple of rubidium standards here in the past. This rather impressive clock has one, and here’s one assembled into a piece of bench equipment. They’re readily available as surplus items for the curious constructor, we’re sure that more will feature here in the future.

Do You Know Rufus Turner?

It is hard to be remembered in the electronics business. Edison gets a lot of credit, as does Westinghouse and Tesla. In the radio era, many people know Marconi and de Forest (although fewer remember them every year), but less know about Armstrong or Maxwell. In the solid-state age, we tend to remember people like Shockley (even though there were others) and maybe Esaki.

If you knew most or all of those names without looking them up, you are up on your electronics history. But do you know the name Rufus Turner?
Continue reading “Do You Know Rufus Turner?”

400 Transistors and 1800 Resistors Form This 1967 Personal Computer

What kind of computer could you build in 1967? Well, if you were reading Wireless World (a UK magazine) and had a good bit of spare cash, you could build [Brian Crank’s] Wireless World Computer. You only needed 400 germanium transistors, 1800 resistors, and an odd number of capacitors, switches, diodes, and neon bulbs. You also needed a good bit of patience, we suspect.

In 1967, the computer cost about 50 pounds to build (perhaps $125 at 1967 exchange rates which would now be about $900 in today’s money). To save parts (and thus money and build complexity), the computer used a trick: it processed data one bit at a time. Many older computers did this, including another UK computer named EDSAC.

Continue reading “400 Transistors and 1800 Resistors Form This 1967 Personal Computer”

Graphene Grown on Semiconductors Big Step Toward Manufacturability

No modern technology has been met with more hype than graphene. These single-layer sheets of carbon promise everything from incredibly efficient power grids to more advanced electronics to literal elevators to space. Until now, though, researchers have yet to produce graphene sheets or ribbons in a reliable way. Researchers at the University of Wisconsin at Madison and the US Department of Energy Argonne National Laboratory have done just that, growing graphene nanoribbons on the surface of a germanium crystal.

By using a germanium crystal as a substrate, the researchers have found a directionality to the way these graphene nanoribbons form. This has been a problem for researchers experimenting with graphene microelectronics in the past; labs experimenting with making transistors out of carbon nanotubes found growth is highly unpredictable. The controlled growth of graphene nanoribbons opens the door to more precise fabrication, something that is necessary for microelectronics fabrication.

Synthesis of nanoribbons this small have not been possible before. Because germanium itself is a semiconductor – and was used for the first transistor – this discovery may pave the way for the creation of graphene-based circuits grown using the same semiconductor fabrication processes used today.

Retrotechtacular: The Genesis of the Transistor

Few births are easy. Even fewer result in a Nobel Prize, and hardly any at all are the work of three men. This 1965 film from the AT&T archives is a retrospection on the birth of the transistor nine years after its creators, [Walter Brattain], [John Bardeen], and [William Shockley] received a Nobel Prize in Physics for their discovery and implementation of the transistor effect.

The transistor is the result of the study of semiconductors such as germanium. Prior to the research that led directly to the transistor, it was known that the conductivity of semiconductors increases when their temperature is raised. The converse is true for metals such as tungsten. Semiconductor conductivity also increases when they are exposed to light. Another key to their discovery is that when a metal such as copper is in contact with a semiconductor, conductivity is less in one direction than the other. This particular property was exploited in early radio technology as seen in crystal radios, for copper oxide rectifiers used in telephony, and for microwave radar in WWII.

After WWII, AT&T’s Bell Labs put a lot of time and research into the study of semiconductors, as their properties weren’t fully understood. Researchers focused on the simplest semiconductors, silicon and germanium, and did so in two areas: bulk properties and surface properties. During this time, [Shockley] proposed the field effect, supposing that the electrons near the surface of a semiconductor could be controlled under the influence of an external electric field.

Continue reading “Retrotechtacular: The Genesis of the Transistor”