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.

From the mailbag: Fun soldering

Eric wrote in to say:

It was fun. It was fun to build the Larson Scanner. It was fun because I successfully put it together and it worked as designed. It was so fun I’ll do this again!

In the mid 70′s I attempted to construct a Radio Shack short wave radio kit with a soldering gun. That’s right, I used a soldering gun. Believe it or not, it worked … as a battery heater upper.

Thank you for the helpful instructions and well designed kit. It’s nice to know that 40 years after my last kit, I can drop the battery killer nickname.

LED Robot Sign

Krummrey shared an LED Robot Sign tutorial on Instructables using one of our original Peggy boards. (Peggy 2 would work for this, too.)

I don’t solder the LEDs in. That way I can just pull them back out and make a new sign when I get tired of the current one.

That big pile of LEDs looks like so much fun! He also posted some more sign designs at the end of the instructable.

Ingenious 1970′s Technology: The Flip Flash

FlipFlash 5

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?

Continue reading

3D LED POV Mirror

“We Are with You, Mirror” is a piece by Brady Marks from VIVO Media Arts Centre that was shown at the Vancouver Mini Maker Faire. It is a 3D persistence of vision volumetric display that acts as a mirror, using four spinning Peggy 2 boards to reflect visitors movements in low resolution 3D LED glory.

Thank you to Brady for sending in the video!

BAMF 2014: Open Source Sprinkler Controls

BAMF 2014 140
BAMF 2014 141
BAMF 2014 142
Part of our continuing coverage of highlights from the 2014 Bay Area Maker Faire.

We can’t say how many times we’ve heard people ask questions about hacking or building their own sprinkler controllers, but apparently here are the ones that everyone has been looking for. These open source hardware sprinkler controllers from Ray’s Hobby —  designed so that you can hack and build your own — look well-made and genuinely useful. There are neat irrigation (and multipurpose relay) controls, including Arduino-flavored variants as well as versions for Raspberry Pi and BeagleBone lovers.