Our two “dis-integrated circuit” kits are the Three Fives Discrete 555 Timer, and the XL741 Discrete Op-Amp. These two kits are functional, transistor-level replicas of the original NE555 and μA741 (respectively), which are two of the most popular integrated circuits of all time.
Last year, we wrote up a detailed educational supplement for the Three Fives kit, that works through its circuit diagram and discusses its principles of operation down to the transistor level. Today, we are doing the same for the XL741 kit, and releasing an educational supplement that explains how a ‘741 op-amp IC works internally, down to its bare transistors and resistors:
This ability to peek inside the circuit makes the XL741 a unique educational tool. In what follows, we’ll work through the circuit diagram, discuss the theory of operation of the ‘741 op-amp, and present some opportunities for experiments and further exploration.
You can download the supplement here: XL741 Principles of Operation (1.1 MB PDF)
- Get the XL741 kit at our store.
- Our original article here, announcing the XL741 kit
- Main XL741 documentation page at our documentation wiki
Steve W. wrote in to share his improvement on the method for making wire bundles we wrote about:
I’ve used the bend-it-over-and-stuff-it-in-the-chuck approach, but was not fully happy with it.
So I drilled a 1/8″ hole in the back of a binder clip. The drilling is easy if you clip a ~3/8 scrap of wood.
A 4-40 SHCS screw long enough to allow me to actuate the clip was not threaded all the way to the head, so I used a 1/4″ spacer between the binder clip and the 4-40 nut. (Pan head screws are usually 100% threaded, but I would have had to look in the dreaded ‘other’ box to find one of those). Having the nut up against the chuck acted as a lock-nut. I had been surprised when I first tried this that I did not have to work harder to keep it from loosening. I had expected I might need a lock washer, and/or a second nut to lock the first.
Just grabbing the wires with the binder clip (my original plan) was not secure. So I wrap the wires 180 degrees around a screwdriver bit and put that in the clip.
Works great, and it is quick to pop in and out when twisting many groups of wires.
Thanks for sharing your hack and sending the photos!
The article Can Analog Circuits Inspire Budding Engineers? over at Planet Analog discusses preparing students for dealing with real world circuitry by getting them started with analog circuits.
By building, probing, and observing the signals and their changes in these circuits without any code requirements, students can get a real feel for otherwise abstract concepts such as voltage, current, and more.
The author uses examples of projects and kits including our very own Three Fives Kit.
Look what just arrived in the mail– Blinky AVR Earrings!
Four blue LEDs blink in sequence, powered by a CR1220 battery. The board is traditional OSHPark purple, with an ISP header for convenient reprogramming. They’re lighter than they look and quite comfortable.
Thank you, Rick! I know what I’ll be wearing to Maker Faire!
Forrest shared these pictures of his Interactive Game of Life build.
I bought the project to help expose my two grandsons to electronics and learn how to build circuit boards. Dan my 10 year old did one board all by himself just using your instructions. Josh my 14 year old did more than half of the boards and I finished them up because I only have the kids for limited time periods. I am so proud of them. Josh complete understands how the Game Of Life works…I don’t HA! We are planning on adding a instruction board to the bottom of the display so other kids can have fun.
I have a CNC router and built the frame. The boards are screwed onto a piece of 1/4″ plywood which floats in the frame. Not glue in. I machined a loose slot around the inside frame pieces. That way I can take the frame apart and easily change out of a board if necessary. It has been so much fun to build and you have SUPER service.
We thank you so much and would like to build more projects that you may come up with. As soon as I get more time with Dan we are going to build the clock.
He also shared his case design (105 kb dxf). Thank you for sharing your time and skills with your grandkids, and for sharing your pictures and design with the rest of us!
I got the @EMSL Meggy Jr RGB working with the @MakerSylvia WaterColorBot. My code is here. https://github.com/docprofsky/meggyjr-cncserver.
The output looks great, too. Thanks for sharing your code, Schuyler!
As before, we cut the parts out on the CNC router from our original design.
The parts were glued together and sanded.
After assembly was lasering to mark and etch the notch, which we carved and chiseled to make it deeper than our previous one.
The first layer of paint was primer grey, followed by black and silver. Once the body of the chip had a beautiful matte black finish, it went back into the laser for the manufacturer’s mark before a final protective coat of paint.
It posed for a few pictures before heading off to meet Sparky, and we’ve posted them on flickr.
The original Sparky design side-by-side with the plush puppet and its new chip.