Chapter 24 - Circuits & Semiconductors #
When I was a kid I thought about circuits as being alive, like Cells at Work!, only little electrons going around busily keeping the heart of my toy working instead of anthropomorphic red blood cells working in the human body.
Now, as an adult - and a computer and electrical engineer at that - I still find this thought endearing. Though I’ve now come to see the physics and art of electronics to be even more beautiful when their true nature is really understood.
There’s a joke you’ll hear about those that work with these low level physics or that arrange logic gates to make full CPUs- that our job and passions boil down to teaching rocks to think.
So, let’s lean how to teach some rocks.
Chapter 24.1 - Semiconductors #
TODO, looks very good briefly scrolling through it: https://lcamtuf.coredump.cx/electronics/
Digilent’s ‘Real Analog’ course looks okay too, and I might write this guide assuming their analog parts kit: https://learn.digilentinc.com/classroom/realanalog/
[TODO] pic of silicon bulb
P/N junctions, etc.
Diodes, the one way road #
A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other.
Diode page on Wikipedia (which is actually superb)
Alright, so in very basic terms, it’s a part that only lets current flow in one direction (ideally). A one-way road for current. If you put a sine wave in, you’ll get a sine-wave chopped in half out. Now, this assumes everything is ideal, as you’ll really get more like the top 40% of the wave out, but we’ll get to those details in a bit. For now, I recommend watching these videos:
zeener, normal, bipolar
- varistors , sparkgaps
- Leds - getting current both ways, LED safety
Diode Logic #
tubes and how they work
PNP V NPN #
Integrated Circuits #
Archive.org backup of the above embedded tweet
Distortion pedal with all homemade semiconductors, only one external component (cap for AC coupling) pic.twitter.com/M7t3Gl1m5P— Sam Zeloof (@szeloof) July 6, 2020
Archive.org backup of the above embedded Tweet + Archive.org copy of the image
Finally I learned how to do focus stacking with my macro (non-microscope) shots. 226 shots, 50µm camera shift per frame. Laowa 25mm F2.8@F4 on WeMacro rail. Stitched in Helicon Focus (pyramid, smoothing=1). 1 original photo for comparison. #WeMacro @laowa_lens #heliconfocus pic.twitter.com/yCdCIBXMRv— Zeptobars (@Zeptobars) March 12, 2019
555, OpAmp, 74-Series Logic #
[TODO] note on price of chips that solve bigger problems - integrated filters, PLLs, VCAs, basically everything on this list
Chapter 24.2 - Op-Amps & Filters #
These things aren’t actually ideal! #
- Not all OpAmps are rail-to-rail, meaning if you give them -12 and +12 V rails, you may only be able to hit -10 and +10 or so.
- OpAmps really need clean power. If you don’t put a small cap to filter the power right at the OpAmps VCC and Gnd pins, except noise.
- There will almost certainly be at least a little bit of DC shift in the output
- You do not actually have infinite gain
- You do not have infinite bandwidth
- They do not actually have infinite input resistance, it’s just really high.
- … See Real op amps, non-ideal aspects (Iowa State University : EE 230, PDF)
Optical Electronics #
Opto Isolators, Vacttrols, Photoresistors
Crystal Oscillators #
Active Filters #
Audio Devices #
speakers, piezos, amps, mics and pickup patters
add motors, analog meters, various connection standards, radio, flex/pressure sense, grounding (chassis, digital, analog, ground planes, etc.), solar/photo reactive,
Relating AC and Music #
Relate back to things like ADSR, Distortion, Reverb / Echo, Decibels (audio), etc. Use VCV RACK
Chapter 24.3 - Displays #
Ther are many Reasons to Question Seven Segment Displays (Harold Thimbleby), especially today, as using literally anything else has gotten significantly easier.
[TODO] Eink, OLED, TFT, etc.
Also, you may want to be able to update your display quickly, so keep in mind if your controller/device has either a native video output, or at least DMA that you can abuse (Just another electronics blog).
Chapter 24.4 - Safe Circuits #10 Ways to Destroy an Arduino (Rugged Circuits)
Chapter 24.5 - Parts & Tools you’ll want to be aware exist #
- Logic Level Shifters
- LED Matrix Drivers
- TL431 - Programmable Reference
- Ferrite beads
- Spark Gaps
- Filter ICs
Chapter 24.6 - Rare and Dangerous Components #
- Tesla coils
- High voltage/current/hot/whatever
- Don’t pretend to be an electrician
- Don’t use ATX psus for dumb things
- Some Components Are Just Bad, Like this USB-C Connector (Hackaday)
- Tubes, NOS parts, etc. - TODO: CRTs and Aquadag
Continued Reading: #
At this point I highly recommend ‘Practical Electronics for Inventors’ ISBN 978-1259587542, namely chapters 2-12, and 15-16. It’s a very large, detailed book that does its best to keep things, well, practical.