Components: Transistors

Another component. Fun, right? Well this component is absolutely necessary to circuitry. Without it, almost every circuit out there would become useless if it suddenly disappeared. So, now that you're thinking, you're probably wondering what it does. Well, simple! Transistors are like an automated switch. It's almost like some of the switches we saw a few posts back, except you're essentially having a current of electricity to flip the switch rather than your finger, making it, in my opinion, one of these some of the most useful components out there.

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Transistors are actually categorized into two main categories: NPN and PNP. This stands for "negative positive negative" and PNP stands for "positive negative positive." They're basically opposites. Why is it named that? Well, look at the picture above. If you look at the bottom right picture, you'll see that rectangle is split into three portions: the collector, base, and emitter. The collector is like the first lead in a SPST switch, the base like the toggle, and the emitter like the other lead of the switch. If you were to use one for switching, you would basically have the collector hooked up to a positive source, the emitter to your ground, and the base to some sort of signal or pulse. When you apply power to the collector, practically no current flows through when the base doesn't receive a signal. When the base does receive a signal, the current flows from collector to emitter without a problem. This is where the difference between PNP and NPN comes in. The one above is an NPN transistor because positive voltage flows from collector to emitter and uses a positive voltage to trigger the base. The only difference in a PNP transistor is a polarity swap. Instead of positive voltage going in through the collector, it goes in through the emitter and grounds through the base.

So how do these work? No, there's no black magic going on here, it's actually pretty simple. The transistor is composed of three parts, collector base and emitter, that are sandwiched together. All three of these parts are made of silicon, which is a great semiconductor. What's a semiconductor? It's something that conducts electricity with an efficiency between that of an insulator and metal. But there is a difference between the three sections. In an NPN, the two pieces of bread, collector and emitter, are negatively doped. Yes, negatively doped, meaning the silicon is infused with an element with more electrons making it more negative, like phosphorus. Now the base is the opposite, it's positively doped, meaning it's infused with an element with one less valence electron than silicon, like the element boron.  Because the base is positively charged and the two other pieces are negatively charged, the positive base actually steals electrons from the negative sides to fill equalize everything out. The result of this is actually a little barrier-type deal that forms where the bread meets the meat where the base is actually slightly negative, repelling electrons attempting to flow from one end to the other. This barrier is very small and relatively weak, making it easy to break letting current flow through. How do we do this? This where the small positive current from the base comes in. If you look at the picture, you'll see a small plate hovering above the meat. When the plate is positively charged, it attracts the electrons from the collector and pulls it over to the meat. This process actually widdles the barrier down to practically nothing, giving the electrons a straight, undisturbed path from collector to emitter. It's amazing, right? 

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Now that we know how they work, let's apply them. One very basic NPN transistor that is used almost everywhere is the 2N2222 transistor. This one works like any other NPN transistor. There are a few rules we need to follow when using them. There needs to be a level of voltage applied to each piece of the sandwich relative to the other pins. This means that the collector needs to be the most positive, the emitter the least positive, and the base somewhere in between. So in this circuit, you have nine volts reduced by 560 ohms leading to the collector. Since the collector is reduced by more the 560 ohms for it to work, you'd have to use a resistor more resistive than 560. In this circuit, they actually replaced the resistor with your finger. Your finger is pretty stinking resistant than 560 ohms; depending on how far the two wires are separated. I clocked in about 800 ohms with a half inch of Dylan finger with my multimeter. Since the base has a weaker current being supplied to it, the base's current can flow through; resulting in an even weaker output from the emitter. Every thing checks out! So, when you touch the two wires to your finger, the current from the base can flow through, completing the circuit and in turn, illuminating the LED. 

I've only scraped the surface here. There are so many different types of transistors out there that it'll take you a week to learn the fundamentals to each one. There are MOSFETs, JFETs, IGBT, bipolar, junction, Darlington; it's nuts. Here's a Youtube video that will hopefully make more sense to you. I can only do so much here on a blog! The best way to learn, and it's the way I've learned, is online videos, books, and trial and error. Hopefully here pretty soon I'll provide a list of good sources and books you can look at.

Components: Switches

Okey dokey, we all know what a switch is; I mean we all have them in our house, right? You flick it when your lights are off and they suddenly turn on. Now what you may not know is how stinking complicated they can be and how stinking large the variety of switches is. I'm about to unleash a whole new world on you. 

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Look at that big 'ol switch. Looks simple, right? That's because it is. When it's off, you flip it to turn it on. Well, how does it work? MAGIC!! No... it too is pretty simple. There are two main parts to this rocker switch: the actuator and a set of contacts. The actuator... well, actuates and the two contacts sit next to each like a 2x4 that got a few inches cut out the middle. When the switch is "off", the contacts are "open", meaning they're not connected. When the switch is in the "on" position, the actuator connects the two contacts, "closing" them so a current is able to flow through from one to the other.

Now, it gets more complicated. There are many more kinds out there. What if you want to switch two currents at the same time? What if you want one position to close one connection and the other close another? Man that was a mouthful. I bet you had to read it more than once! Anyway... we have a system for this ordeal. A switch that would simply have an off position and one other that would close a connection would be a SPST switch, or a single pole, single throw switch.

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Take a look at this here knife switch. This is a SPST switch. Do you see the "knife?" Well, that's the pole. There's only one pole, or a single pole. This is where the SP in the abbreviation SPST comes from. There's also only one spot the knife slices into. This spot it called a throw; which explains where the ST comes from. Now... why is that connection called a throw? Well, technically in engineer language, when you flip a switch, you're supposed to say throw instead of switch. Why? No clue. Personally, I think it sounds goofy. "Honey, it's dark in here. Would you find throwing the light switch?" Funky. Anyway, that's why this type of switch is called a SPST switch.

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Now this here is a DPDT switch. You see these switches bolted to crazy scientist's lab walls. Now... why is it called a DPDT switch? Let's start with the poles. If you look very closely, you'll see that there are two knives! Bravo, you got it. What about the DT portion of the name? There are two sets of contacts, so it's a double throw. Simple enough! Now, what do you think it would look like if one knife went bye-bye? Well, it'd be a SPDT switch because there are two connections and one knife. What if it had four knives? Then it'd be a 4PDT switch.








Ok. Now, the thing is, you aren't limited to just one or two poles. If you need a switch that makes 1000 different connections, congrats. It's a 1000P whatever throw switch. You are however limited to the number of throws with this specific type of switch. Now there are switches out there that have multiple throws, like the rotary switch, but with the flip switches you'll probably only see a ST or DT switch. So since there are multiple different states each switch can be in, you know, on or off, how would we indicate that? Well, the only factor that affects the number of states is the throws. If you have a SPST switch, there's the off position and the on position so that leads it to be an ON-OFF switch. If you have a switch with two poles, it'd be an ON-ON position. I know I'm stating the obvious here, but you need to know this. Why? Well some DP switches will actually have a middle position in-between the two on positions called the OFF position. This sucker is a life saver because without it, a DP switch would always be on. Always, no matter what. When the switch is in the off position, no current can flow through, which is brilliant. So, a DP switch with an off position would be an ON-OFF-ON. There's an actual reason for this. Push button switches can be momentary or not and they specify this by using the on/off system. If a momentary button only turns on if you hold it down because if you release it, it turns back off. How would you specify the secondary position is monetary? OFF-(ON). The parenthesis tell you the on position is momentary. Man... aren't switches fun? I made all this sound much more complicated than it really is but once it clicks in your head, it really seems simple.

Now, if you'd like to see a nice, wide variety of switches and buttons out there, click here to check them out!

Components: #2 The Symbols

Alright, so understanding the purpose and functions of electronic components is important, but being able to understand various schematics is just as important. You need to know what a schematic is saying so you can replicate it in the real world; this is how you learn. You learn by going along with trial and error.

Take a look at the chart to the left. Here are just some of the symbols used to represent components. There are resistors, capacitors, diodes, transistors, LEDs, switches, relays... you name it. Unfortunately, well, depending on how you look at it, there are a lot of symbols to memorize, but like I said, that can go either way because, sure there may be more symbols out there, but that also means more options when it comes to making your circuits. So personally, I see this as a great thing! I like to have a variety when it comes to designing instead of being restricted to a certain set of limitations. That's just sucky.

Well, anyway... you'll see these symbols everywhere. You even saw them back in lesson #3 with the simple LED circuit. You saw a battery, a resistor, a switch, and of course, the LED. So, yeah. That's all I got for ya. We'll definitely use this very soon when we look over and dissect more complicated circuits in the next lesson or so. Credit for the photo goes to Forest M. Mims III from his engineering mini notebooks.

Components: #1 Intro + Resistors

The electronic components. Your phone, computer, TV, lights, everything out there that feeds off of electricity wouldn't be here without them. Every one of them: resistors, capacitors, diodes, batteries, solenoids, transistors, wires, MOSFETs, gates, ICs, relays... the list goes on and on my friend. Each one of these little wonders has their own unique job, and when you combine these components correctly, you may just come out with something as useful and awesome as a computer. 

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Here are what some of the components look like in the real world. When you're designing a circuit, you don't just jump in and start soldering things together, you design it sort of like you would with a blueprint. Go to a piece of paper and draw it out! Then with a little math magic (or a computer program), you could see if it works. If you want to go onto making circuits, then you're going to need to know what each component does and how to draw it out. 

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The resistor. This component is probably one of the most used ones out there. Remember how back in lesson 2 we didn't want too much coming out of the spout? Reason is, if there was too little resistance, too much would come out and your cup would overflow, but if the resistance was too high and not enough water was coming out, your cup would sit there for days. Well this is why this component is so important. The units used for measuring resistance is in "ohms." Now, looking at the picture to the left, you may be wondering how you can tell how many ohms each resistor provides. Well that's easy. First one is 330, second 33k, 560, 150k and so on. Now, how can I tell? The colored bands that wrap around each one. Black = 0, Brown = 1, Red = 2, Orange = 3, Yellow = 4, Green = 5, Blue = 6, Purple = 7, Grey = 8, and White = 9. Now, if the resistor has three bands and one off to the side, the first two will tell you what the first two digits are and the third will tell you what the multiplier is ("a" and "b" times 10 ^ "x" power) So, if a resistor has, in this order, a red band, a purple band, and a yellow band, you know that the first two digits are 2 and 7 and the multiplier is 10 to the 4th power. Now for the math! 27 x 10^4 = 27k. That resistor is 27k ohms. Pretty easy, huh? It especially is once you have the color codes memorized like yours truly. Blue stands for 5, yellow for 4, grey for 8, black for 0. I am just that good. Now, I said earlier that there is usually 4 bands on there... we only talked about 3. So, what's that fourth band for? Not all resistors are perfect. Some have a plus or minus percentage from the stated value due to it being near impossible to make a component perfect. Now, the color codes are different for this band, but luckily, chances are, you won't need to learn them. The only two you'll need to know it Gold which is +-5% and Silver which is +-10%. So, if a resistor of 220 ohms has a silver band on it, it means the true resistance is somewhere between 198 - 242 ohms. If we have a 1k ohm resistor with a gold band, then the rating will be 950 - 1050 ohms. Easy enough, right? For additional info, click here.