In our consumer society, tons of electronic junk gets thrown away :(
But theres useful stuff in that trash!
Why should you learn electronics? Well, I for a long time wanted to be an electrical engineer, design circuits and all that. Technology is cool! It makes so much of our lives possible, and I just like learning. I soon realized though that my prospects of being an engineer were pretty limited, mainly because of disability, poverty, etc.. But I still learned about electronics because it feels good to learn things - there is such a good feeling of building a circuit over and over again from a schematic and then eventually knowing how it works so well you can make it any time you want without having to look at a schematic!
Electronics isn't for everyone, but if you are here then you are probably at least somewhat interested. I just can't say enough how fun of a thing it has been for me to learn as a craft. Like sewing, knitting, crocheting, modelling, puzzles, etc, it is just a fun and relaxing thing to do for me.
If you take any random piece of electronic junk - boomboxes, recievers, vhs players, whatever - and look inside, well... instead of spending money ordering components, a lot of the basics you can get super cheap at thrift stores, or for free from dumpsters or whatever!
Most e-waste will have $5-10 dollars worth of useful stuff in it! So, its usually worth it to grab something if you need parts. It helps for people like me who are extremely poor.. Some electronics can easily have up to $30 worth of parts in it, plus you don't have to wait for shipping, just head to a thrift store!
Even if you see some electronics in a dumpster or whatever, ive taken perfectly fine working components out of random e-waste i found that had been through rain and snow, that are decades old. Either way, try and find a use for e-waste, because someone died for every single one of those components. Someone's child got sold into slavery to make that resistor, someone in the third world has a horrible congenital disease from the manufacturing processes of those semiconductors.. Pay your respects and have some empathy..
So, first I am going to just give you an overview of what you will find inside e-waste, and a bit about circuits and manufacture. Then we will talk about what each electronic component does.
Open up some piece of electronics and you'll often see tons of components on a board. A secret is that a lot of the time, the circuit is actually really simple, and the number of components doesn't necessarily mean the circuit is complicated. Here is another secret: nobody actually knows what a circuit does just by glancing at it. Reverse engineering a circuit board is frustrating and takes a long time even for engineers, sometimes hours, sometimes weeks. So don't be discouraged.
Often manufacturers only have generic value components so circuit designers will, instead of a single resistor or capacitor, use a few of these components running in series (one after the other) or in parallel, just to get specific values. Doing series/parallel components just to get certain values ads up quickly. A design might be more efficient if it used a 2.43112 KilOhm resistor, but that is not a value of resistor that is manufactured anywhere, so that value has to be made through combining generic value resistors.
While we are talking about manufacturing quirks, another secret that hopefully will be encouraging, is that you can pretty safely assume that a third to half of the stuff on a circuit board, sometimes the majority of them, are doing things that the consumer/user would probably never even notice if they weren't there. A whole lot of the circuitry in most electronics is for error-checking, noise filtering and things like that.
Another thing to know is that fully assembled circuits typically look completely different from the schematic design that an engineer would use to describe the circuit. Schematic designs are usually pretty easy to understand as long as you know how to read them, but assembled circuits take a long time to lay out and a lot of time to understand, even for experienced engineers.
This is because the finished product is three dimensional as opposed to a 2d schematic diagram, meaning that there are very different ways of laying things out. You also have to consider where in the final product the circuit board will be and what shape and size it has to be will constrain you, unlike on a schematic diagram.
Because of this, Every single circuit is its own entire world. You could have two circuits that do almost the exact same thing, but one circuit has just a single extra resistor. That single extra resistor, when it comes to making the final board design, might make the entire final circuit board look completely different from the other depending on where it is needed.
Now take that same situation, and add on the fact that you have parallel and series components to consider, and we haven't even gotten into transistors which have three legs, and IC's which have no less than six and typically more than eight, adding way more complexity to circuit board layouts, and you can understand that electronic design is absolutely maddening. It is kind of insane that anyone agrees to get paid to do it at all, but i guess that is why God invented autistic people like you and me.
All this is to say, circuits are very intimidating, but you should know that the fact that they are complicated and hard to understand is not because you just aren't "smart enough". The complexity is just as frustrating to engineers as to non-engineers. The design is the result of a ton of factors, including fabrication deadlines, overworked and apathetic engineers, weird unforeseen flukes in production, poor project management, et cetera.
Just about half of every piece of electronics i open up has very obvious last-minute changes put in, such as a resistor haphazardly placed on the green side of the PCB to make a connection that wasn't factored into the layout - sometimes i even see absurd things like parts of a circuit which do nothing or are dead ends that the designer just didnt bother removing.
Likewise you will often find circuit boards which were clearly mass-produced for a different purpose, and which are missing a ton of the components because the production company just took an existing board layout and used it for something else. Any time you look at a mass produced circuit board, your first thought, no matter who you are, should be: this. design. is. terrible.
Just take it slow, and understand that one of the skills that engineers have to acquire that is more important than any specific bit of knowledge or talent, is the ability to take things one step at a time, compartmentalize tasks, and be extremely patient. That makes engineering sound a lot more boring than genius inventors sitting around coming up with million dollar ideas in the shower, but it is the truth.
Resistors resist. We are off to a good start.
What does it resist? Well, voltage, but also current. Do not make the mistake i did for a lot of years thinking that resistors only reduce voltage. They are just as often used to limit current.
Do not make the mistake in thinking that resistors simply operate like a "valve" that closes things off a bit - this is a terrible analogy that even a lot of teachers use to introduce resistors. It implies that electricity goes in one direction from point A to point B. This is true in a certain sense, but it gives people the wrong idea. Think of resistors not as a "valve" controlling the flow of electricity from point A to point B, but rather as... well, i don't know, a piece of flair that adds character and style to your circuit :) This is a good way to think of all components. Specifically with resistors, what they do in the context of a circuit is typically to attain specific voltages, because if you have a circuit that runs on, say, 12 Volts, and every part of the circuit just has 12 Volts running through it at all times, well, that circuit probably isn't doing much, it is probably a very boring circuit. Resistors make a circuit more interesting by changing the voltage and current flowing through different parts of the circuit. Variety - or melange, if you will - is the spice of life!
Resistors come in a wide variety of values, from 1 or 2 Ohms, up to kilOhms, hundreds of KilOhms, up to one or several MegOhms. Here is a useful way to think about why different values are used (at least from my experience):
Values under 1k Ohms are often used for current limiting, which is basically just a buffer that protects parts of the circuit such as IC pins, inputs and outputs. these are usually used for power regulators and in that case they can be really big, despite being small in value.
Almost every digital circuit you will come across will use potentiometer and resistor values of 1k or 10k Ohms, sometimes 5k. Aside from that 10k potentiometers are cheapest and mass produced, this is because digital logic usually occurs at 3.3 to 5 volts, and a voltage divider for those voltages will almost always use at least one 1k or 10k resistor.
Audio circuits will have higher values between 100k and 1M. This is because audio circuits typicaly have filters in them, and without getting too much into filters right now an RC filter is made by one resistor and one capacitor - the capacitor is usually a very small value, and the smaller the capacitor value is, the larger the resistor has to be to make the filter work in the audible frequency range. guitars for instance often have pots from 500k to 5M ohms and capacitors of very small value for their tone knobs. Volume knobs in most audio electronics are anywhere from 10k to 500k.
Sometimes resistor values have to be VERY precise and exactly as specified, for instance with digital logic or voltage dividers, but then other times the value practically doesnt matter at all and can be almost anything. Most complete electronics devices will have plenty of resistors of values from 1 ohm to 1MOhm. Industry standardization means you will not run into many resistors with purple, white, or blue stripes on them, they are less common.
LED's. You know what they are. Everyone does. LED's do function as diodes. When you are circuit bending, this can be cool and add some sound-responsive light to the thing. You can also typically use LED's in your circuits that require normal diodes too. The nice thing about LED's is that if you fuck up, they don't light up anymore, so they are pretty good for debugging and troubleshooting. The negative side of LED's is that once they die, they are dead. No more blinky fun lights :( ever again. So, for non-LE D's: why would you use a diode if it doesn't light up? making things light up is fun. Well... yeah...
You are probably gonna come across Zener Diodes and Shotkey Diodes. Both are usually black, with a white band on one end. sometimes they will be little tiny glass tubes with something red in them. Those ones are usually very low value and rated for like 1volt. On the black ones, the white band is the part that electricity "flows to", so the end without white is where you put your "input" that is "from" the "positive" part. I don't really know the difference between Zener and Shottkey diodes, i just know they get the job done if you only want things to go one direction.
Another useful thing with diodes, is you can use them to get a specific voltage that you want from any larger input voltage with a resistor and a diode going to the ground. The diode shunts the excess voltage to the ground, allowing only the voltage the diode is rated for to pass. Good luck ever being able to read the markings on one of these tiny fuckers though to figure out their rating. I usually just guess from context, but i think there is a way to test them with a multimeter but i dont know how those work. You can try to look up their ratings. Shunt regulators have disadvantages and advantages in terms of generating a fixed voltage so do your own research.
Things get a bit more complicated here. Firstly, because there are exactly one zillion different types of caps. You will typically either see them as big(-ish) blue or black cylinders, or as weird tiny brown pancakes with legs, or as stupid green blobs that are kind of rectangular. There are also capacitors which are box-shaped, and these are conveniently pee-colored to differentiate them from crystals.
Capacitors hold electric "charge" (whatever that is) in a "feild" (????). Nobody knows what this actually means. Basically, inside them there are two plates, one positive and one negative, that are separated by a really really tiny distance. In between the plates, electrons hang out. But, when a capacitor reaches its maximum holding capacity of electrons, it discharges them.
If only the carceral state were so merciful.
Because reaching capacity takes time, capacitors usually do time-related stuff. This sounds cool, but also kind of uselessly vague, so let me tell you some of the secret things you can do with caps:
1. Create a high-pass filter: For the most part, if you are dealing with an active circuit you can make a high-pass filter with just one capacitor. Otherwise, you can make one like shown below. If you think of electricity as a drum roll humming along, a high pass filter turns the drum roll into just a single hit on the drum, or a roll that fades out over time.
The  is a capacitor, the | is a resistor.
2. Filter out noise from a Direct Current: If you have DC, such as a power supply, or a fixed voltage being used for something, you can, in a rudimentary way, filter out some of the noise on that DC by putting a capacitor between the positive and negative, as shown below. Make sure that if you do this with an electrolytic (cyclindrical) cap, you get the polarity right, and that it is rated to handle the voltage involved.
Most of the time, capacitors are used for these two purposes: filtering noise, and blocking DC from flowing constantly, instead only letting it flow for a short period of time after being connected.
Because capacitors store an electrical charge, if you use a capacitor to filter your power supply (ideally something like a 10uF to a 100uF cap), you will notice that after you unplug the power, the circuit still works for a little bit, slowly dying out. This is a really useful thing to be able to do, and has a lot of applications i will get into later.
i don't feel like talking about them. i have literally never used one. They are usually kind of a sea green color and look like resistors, or they come in the form of a weird loop of wire sticking out of the board. Their value is measured in Henries... That alone is stupid enough in itself to completely disregard them.
Crystals are powerful and useful because they resonate at extremely precise frequencies when a very tiny amount of electricity is run through them. You can usually find them in the form of a kind of long, metal oval thing that is flush against the circuit board, and (usually) located right next to a microchip. All you really need to know is that microcontrollers run on clocks. You can think of the frequency of the crystal as the speed of the micro's clock. Ever time the crystal cycles between high and low, the microcontroller is able to do a very simple instruction. When you consider that the microcontroller is running in Millions of Hertz - millions of clock cycles per second - you can appreciate how awesome digital technology is. Yes analog is neat, but think of what an amazing feat of engineering digital logic is. Even a very simple little chip can complete millions of instructions per second. These instructions are usually simple things like addition, subtraction, multiplication, exponents, setting inputs and outputs high or low, and so on. but you can pack a ton of instructions into just a few hundred bytes of code using microcontroller programmers.
i will talk about microcontrollers separately. but anyway, for most folks crystals arent that useful unless you are doing stuff with microcontrollers or radio frequencies, and scrapping them isnt reliable because tere is typically only one or two in any device, and the frequency of the crystal is not likely to be the one you are looking for.
transistors almost always have three legs, the middle one typically being very sensitive. They come in the form of Bipolar Junction Transistors - BJT - or Feild effect Transistors - FET. it doesnt matter what any of those words mean really. how transistors work is that they have inside of them different semiconducting materials, which is exactly what it sounds like: a material which conducts electricity, but only under certain conditions. The "condition" for most transistors is the voltage present at the Base (usually middle) leg of the transistor, which turns on or off or amplifies the current flow between the Collector and Emitter.
BJT's are typically described well enough as basically two diodes connected together, with a lead in the middle. There are two types of BJT: the NPN and the PNP, which referse to the Positive or Negative polarity of the three legs (i think?) . either way, i tend to find that with NPN's you can treat them like a voltage controlled switch, connect the collector to your signal, the base to the control signal, and the emitter to where you want the electricity to go. To use a transistor as an amplifier, you need to bias the transistor by adding a positive voltage to the collector and the base, ensuring that you don't over-current and have electricity flow backwards into your "input" by using a simple resistor.
FET's i dont really know anything about. If you find some, keep them though because they are very useful for building high-powered amplifiers and things like motor controllers. there are several different ways to use them, but they do require you to be a bit more careful because they can get very hot and usually therefore need a heat sink attached, and they also can output relatively high voltage alternating current, which is not very nice to accidentally touch.
you can find plenty of simple circuits to make amplifiers and voltage-controlled switches with BJT's, and BJT's are SUPER easy to come by. radios and boomboxes and stuff like that will have dozens of them inside, easily $5 to $10 worth of transistors. transistors do take some time to get used to, they can operate in a not intuitive way and you have to pay attention to polarity and current to avoid frying them. but, if you learn to make voltage amplifiers and voltage-controlled switches, those indeed are two of the most important things to know how to do with electronics, and knowing how to make those you can make just about anything! yes REALLY!
The most common IC you will come across by far are operational amplifiers. From their name, you would assume that they work like typical audio amplifiers, but this is not necesarily the case. Op amps can serve as amplifiers for audio signals, but they can also serve as comparators, Schmitt triggers, active filters, rectifiers, digital-to-analog converters and vice versa, voltage and current regulators, and many others. Often times, audio amplifier chips are different and specifically designed for audio, while op amps are more versatile. I will talk more about them elswhere, but just know that they are really powerful and useful, but like transistors, take some getting used to because they don't work in a very intuitive way.
Apart from op amps and microcontrollers, a lot of what you will find are digital logic chips and counters. It might seem like they are only really useful for very specific things, but digital logic can be used to do a ton of stuff, so simple logic chips like decade counters, AND/NOR/NAND gates, Shift Registers, Schmitt Triggers and so on, are pretty common to find in various electronics. These simple logic chips are also super cheap, which is why you can often find them in place of a dedicated MCU. With frugality and some clever design a lot of what could be done with a bespoke microcontroller can just as well be done with logic chips, for instance controlling LED interface, cycling through different modes of a device, lots of stuff.
MCU's, as i said earlier, are basically entire computers on a chip. sometimes you will find ones that can be repurposed, but a lot of them time they are covered in a blob of epoxy or have their identifying markings rendered unreadable. they tend to be proprietary. with an enormous amount of dedication, they can actually be repurposed and re-programmed sometimes with different firmware. MCU's are programmed using a Serial interface, which is a very long sequence of 1's and 0's, sent at a very high speed, which configure the transistors and logic inside the MCU. i guess i will add a little section here on Serial interfaces.
The form of digital data transmission you are most familiar with is USB. it stands for Universal Serial Bus. Universal means that it can do almost anything, Bus means that it is like a bus that transports things. Serial refers to the way that information is sent: in a serial sequence, one bit at a time. Everything that goes through your USB cable is just 1's and 0's being transmitted at extremely high speed. we already know this from above. this is also how dogota;ldata is stored, as transistors which are set to either on or off position.
Digital data is, then, stored in the form of switches between 1 and 0. The smallest amount of information is called a bit, and it is either a 1 or 0. A byte is a series of 4x4 or 8 bits like 0010 0111. One byte can represent any value between 0 and 255 in computations. since 0 is consider as a value, this technically gives us 256 values. "Words" are the smallest compilable amount of data the computer uses. Eventually, after 8bit, then 16bit, we had computers with 32-bit Words, which means each "word" is made of 4 bytes. If each byte can represent 256 values, 32-bit words can represent values up to 1024 using only 1's and 0's.
For more interesting notes on the sacred geometries of binary computation, see The Mystery Of Binary by Viznut.
For the purposes of this little introduction, I will talk about the types of digital things you are likely to run into scavanging e-waste and examining bits of junk.
something you will run into are Analog-Digital converters and vice versa. ADC's and DAC's are foundational for multimedia video and audio. It allows you to use binary, digital computation techniques to generate varying voltages. Digital circuits only output 1 or 0, so how do you get a varying voltage? well, same way as with analog stuff: resistors. At least, usually. there are other ways, but the most common and easiest way is to use resistors. Say you have 8 pins that are outputs of a digital chip, and each pin is connected to an output. If you have a ladder of resistors, in increasing resistance, along those 8 pins, you will then get different voltages from each pin. Combine them together and you can get different voltages depending on what pin (or combination of pins) are turned on or off. Microcontrollers do this by assigning a 1 or 0 to each pin. with 8 pins you can have one byte of Bit Depth, which is how you measure the resolution or quality of the output of the DAC.
More to come soon