About Windell

Co-founder of Evil Mad Scientist Laboratories.

The XL741 Discrete Operational Amplifier

Ever since we released our Three Fives discrete 555 timer kit last year, people have been asking us “When are you going to come out with a 741 op-amp?” It has taken us quite a while to get here, but the answer is… Today!

Our XL741 Discrete Operational Amplifier is a real, working op-amp that you can build yourself.  It’s a transistor-scale version of the original μA741 integrated circuit, that incredibly versatile and popular analog workhorse. As with our 555 kit, you can probe inside to see the inner workings of the circuit as it works. And, like our 555, it comes with a beautiful anodized aluminum “IC legs” stand, so it even looks great when it isn’t plugged in.

The kit was designed and developed as a collaboration with Eric Schlaepfer, and is a direct adaptation of the equivalent schematic from the original Fairchild μA741 datasheet.

If you’ve ever used operational amplifiers, you’re probably familiar with the μA741 (or colloquially, just “the 741″). Designed by Dave Fullagar and released by Fairchild in 1968, it’s the quintessential and most popular op-amp of all time. While newer op-amp designs easily outperform the μA741 in just about every possible respect (speed, noise, voltage range, and so on), the 741 remains widely beloved and in active production by multiple manufacturers even today — over 45 years later.

And, if you haven’t used an op-amp, this a great way to learn. Op-amps are simple, wonderful building blocks for making analog computers. With op-amps, you can build circuits that can (for example) add, subtract, amplify, take logarithms, perform integration, or perform other operations on your signals. Or buffer and copy them, or cleanly convert current to or from voltage, and on and on and on.

A regular op-amp is an integrated circuit; a little black box. The XL741, on the other hand, is a big black box, with a heck of a lot of points where you can can probe inside, to see what’s going on, in real time. And that’s a unique opportunity.

The XL741 is a quick, easy to build soldering kit, with through-hole components, and not too many of them. (And, have you see our awesome resistor wallets?)

And, best of all, the XL741 is in stock, and begins shipping today. 

Visit our store page for links to the XL741 datasheet, assembly instructions, and additional documentation resources.

Linkdump: July 2014

Comet 67P/Churyumov–Gerasimenko nucleus

A Fragment of Muonionalusta

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This little chunk of crystalline metal is a tiny slice of a meteorite — a rock that fell from the sky. When one says that, the next natural question is, “how do you know it’s a meteorite?” (We will get to that.) But what is really staggering is not just that we know, but how much we know about it and its history. And what a long history it is.

This specimen is a 68 gram sample cut from a fragment of the Muonionalusta meteorite.  According to our best current understanding, the parent body that Muonionalusta came from was one of the earliest bodies to take shape during the formation of our solar system. It began as a protoplanet (or planetisimal) that accreted within the protoplanetary disk that would eventually become our solar system. It accreted over the course of roughly the first million years after the beginning or our solar system. (That is to say, during the first million years after the very first solids condensed from the protoplanetary disk.) The parent body had an iron-nickel “planetary” core, 50–110 km in radius, that was eventually exposed by collisions that stripped away most of its insulating mantle. It cooled very slowly over the next 1-2 million years. It is estimated (with startling precision) by Pb-Pb dating that the body crossed below a temperature of ~300 °C at 4565.3 ± 0.1 million years ago, just 2-3 million years after the solar system began to form. For the next four billion years, it led a largely unremarkable existence as an asteroid (minor planet) until it broke apart (possibly due to a major collision) about 400 million years ago. Then, one fine day roughly one million years ago, a large fragment entered the earth’s atmosphere, breaking into hundreds (perhaps, thousands) of smaller fragments that rained down in a shower of fire upon what is now northern Sweden and Finland. Four ice ages transported the surviving meteorite fragments across the Swedish tundra, until their first discovery (and naming after the nearby Muonio river) in 1906.

But, how do we know all of that?
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Electro-Kistka: Dyeing an Egg in Place?

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In our annoucement article about the EggBot Electro-Kistka — the hot wax dispenser for the EggBot — we noted that it can be challenging to reposition an egg after taking it out to dye the egg between wax layers.

As an alternative suggestion, reader Dan commented:

Could you leave the egg in the EggBot and paint on the first layer(s) of dye with a brush? Then dip the egg for the last layer to get the ends covered.

Well, let’s try and see how it turns out!

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Ingenious 1970′s Technology: The Flip Flash

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Once upon a time, cameras did not come with LED illumination or even xenon strobes, but rather with a socket that could fire a one-time-use flashbulb.

An advance from this was the “flip flash” cartridge which held 8 or 10 flash bulbs, ganged up so that you could take one photo after another, without pausing to swap bulbs. Each time that you took a picture (exposing actual film!), the next flashbulb in the cartridge would fire.

But you might ask a tricky question here: How does it know which bulb to fire next?

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A Giant Breadboard for the Giant 555

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One of the common reactions that people have when they first see our Three Fives kit is to joke “Now all I need is a giant breadboard!”  Well, Michael Pechner actually designed and made one, and put the files up on Thingiverse.  He built the design in Fusion 360 with a little help from Michael Gregg and printed it out in PLA ABS on his 3D printer.

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Thus far, the design is “plastic only,” without the metal inserts that one would find in a real electronic breadboard — but that’s okay, since the aluminum legs on the Three Fives kit are also decorative rather than functional. But, there are holes in the tops and slots in the bottom in case someone would like to add them.

 

Kids Hack Day

Inspired by the global hackerspace movement and (software) hack days, Kids Hack Day is a 1-day event held in various locations around the world, where children and adults come together to “hack” and make new uses of every day items.

This incredibly charming video from the Kids Hack Day kickoff event in Moscow on May 25 shows you what it’s all about. (And, we are tickled to see our own WaterColorBot and EggBot making little appearances as well.)

It’s Just Math

image by Bryan Kennedy
I loved this little piece by Bryan Kennedy titled “It’s just wood.” A concise philosophical statement about the freedoms that come along with knowing how to make things.

The same approach applies in so many different contexts.  Sometimes, it’s just aluminum, just software, or just silicon. It also reminds me of what a physics professor of mine used to say when explaining how simple something was: “It’s just math.”