Pillaging The Wealth Of Information In A Datasheet

It’s a fair assumption that the majority of Hackaday readers will be used to working with electronic components, they are the life blood of so many of the projects featured here. In a lot of cases those projects will feature very common components, those which have become commoditized through appearing across an enormous breadth of applications. We become familiar with those components through repeated use, and we build on that familiarity when we create our own circuits using them.

All manufacturers of electronic components will publish a datasheet for those components. A document containing all the pertinent information for a designer, including numerical parameters, graphs showing their characteristics, physical and thermal parameters, and some application information where needed. Back in the day they would be published as big thick books containing for example the sheets for all the components of a particular type from a manufacturer, but now they are available very conveniently online in PDF format from manufacturer or wholesaler websites.

A 2N3904 in a TO92 through-hole package
A 2N3904 in a TO92 through-hole package

Datasheets are a mine of information on the components they describe, but sometimes they can be rather impenetrable. There is a lot of information to be presented, indeed when the device in question is a highly integrated component such as a DSP or microprocessor the datasheet can resemble a medium-sized book. We’re sure that a lot of our readers will be completely at home in the pages of a datasheet, but equally it’s a concern that a section of the Hackaday audience will not be so familiar with them and will not receive their full benefit. Thus we’re going to examine and explain a datasheet in detail, and hopefully shed some light on what it contains.

The device whose datasheet we’ve chosen to put under the microscope is a transistor. The most basic building block of active semiconductor circuits, and the particular one we’ve chosen is a ubiquitous NPN signal transistor, the 2N3904. It’s been around for a very long time, having been introduced by Motorola in the 1960s, and has become the go-to device for a myriad circuits. You can buy 2N3904s made by a variety of manufacturers all of whom publish their own data sheets, but for the purposes of this article we’ll be using the PDF 2N3904 data sheet from ON Semiconductor, the spun-off former Motorola semiconductor division. You might find it worth your while opening this document in another window  or printing it out for reference alongside the rest of this article.

Let’s take a look at all the knowledge enshrined in this datasheet, and the engineering eye you sometimes need to assign meaning to those numbers, diagrams, and formulas.

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Retrotechtacular: MONIAC

There is an argument to be made that whichever hue of political buffoons ends up in Number 10 Downing Street, the White House, the Élysée Palace, or wherever the President, Prime Minister or despot lives in your country, eventually they will send the economy down the drain.

Fortunately, there is a machine for that. MONIAC is an analogue computer with water as its medium, designed to simulate a national economy for students. Invented in 1949 by the New Zealand economist [WIlliam Phillips], it is a large wooden board with a series of tanks interconnected by pipes and valves. Different sections of the economy are represented by the water tanks, and the pipes and valves model the flow of money between them. Spending is downhill gravitational water flow, while taxation is represented by a pump which returns money to the treasury at the top. It was designed to represent the British economy in the late 1940s as [Philips] was a student at the London School of Economics when he created it. Using the machine allowed students and economists for the first time to simulate the effects of real economic decisions in government, in real time.

So if you have a MONIAC, you can learn all about spectacularly mismanaging the economy, and then in a real sense flush the economy down the drain afterwards. The video below shows Cambridge University’s restored MONIAC in operation, and should explain the device’s workings in detail.
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DIY Thermal Imaging Smartphone

We wish we had [Karri Palovuori] for a professor! As an exciting project to get incoming freshmen stoked on electrical engineering, he designed a DIY thermal-imaging smartphone that they can build themselves. It’s all built to fit into a sleek wooden case that gives the project its name: KAPULA is Finnish for “a block of wood”.

It’s just incredible how far one can push easily-available modules these days. [Karri] mounts a FLIR Lepton thermal camera, an LPC1768 Cortex M3 ARM micro, a GSM phone module, and a whole bunch of other cool stuff on a DIY-friendly two-sided board. The design uses 10 mil (0.25mm) trace and space, which is totally achievable with home etching methods. Copper wire bits fill up the vias. Did we mention he’s making the students do all this themselves? How awesome is that?

[Karri] expects that the students will tweak the software side of things. With additional onboard goodies like an accelerometer, microphone, speaker, SIM card, and USB, it’s not likely that they’ll get bored with the platform. He has a stretch hope that someone will take the hardware and modify it. That’s ambitious for sure, but it’s so cool that someone could.

We’ve seen some sophisticated DIY cellphones before, but this one rises above by being easily DIYable and including awesome extra features. Order parts now, and start etching. You could be sending thermal-photo tweets inside of just a few days.