How To Read Electrical Schematics

nothing like a good read of schematics welcome to hack a week you know at first glance a schematic to be a pretty intimidating thing to look at for instance here's a power supply now to those of you that don't know what any of this stuff means it just looks like a bunch of lines and silly little symbols and what the hell is it all about well today I'm going to show you how to read a schematic just the basics anyway and the best place to start out there's all those lines that connect the components together let's take a look at a simple drawing I've done here here's a resistor here is a transistor and a capacitor another resistor now let's say that this connection has to cross over this line sometimes people will just simply draw them like that and how do you know if that's connected right there or not well there's a couple of ways to take care of that sometimes people draw them like this it's just a line going over a line and it's assumed that those lines don't connect now if you want to show that those lines do connect put a big ol dot right there and what that says is yes all four of these this is a junction where these things have to connect with each other now there's another way to draw it if it doesn't connect and that is to just simply draw all over the other line that says that this wire comes across jumps over and goes here and is not connected to this line okay so that's some of the basics that we need to start with on how things connect that's is very important because a lot of people make mistakes with those lines when they cross each other so if you don't see that dot there that aren't connected if you see a dot there it is connected and of course the home would indicate that they're not all right let's look at some components now we'll start out with the most basic component out there a resistor resistor resists the flow of electrons through it that resistance is expressed in a value called ohms we'll get into that in another video this is what the symbol looks like just a straight line with some ziggy-zaggy lines going like this to another straight line that is a resistor sometimes you'll see next to it and are with a number next to it r2 let's say that it says that that would be that's resistor number two and then usually there will be something like this written next to it 100 K so that means K is a thousand that's one hundred thousand ohms sometimes you'll see it expressed as ohms the symbol for ohms looks like this so you may see something that just says 1 ohm so that's exactly what that would be so that's what a resistor is and that's usually the way they're drawn now a variable resistor that being like a volume knob that you would turn on a amplifier something like that sometimes there's little trimpots anything that's variable usually has an arrow pointing at it like that that means that it has three leads on it this one right here makes it a variable so that's a variable resistor or a potentiometer another thing you'll see on a resistor symbol is the watt rating so you may have a resistor here and it might say 100 if you don't see anything after it that would mean it's a hundred ohms and then it will have a watt rating and that watt rating may be 1/4 for the W it could be 1/2 it could be 1 but it will have a W next to it a photocell or a light dependent resistor also abbreviated LDR will have the resistor symbol we'll draw it a different way this time and it will have two arrows pointing at it at an angle indicating that light will change the resistance of this now of course without power a circuit doesn't do too much sometimes it can but most of the time it needs a power supply there's symbol for batteries that looks like this and a smaller line and something like that the smaller line is the negative the bigger line is the positive that's the symbol for a battery that's a single cell you may see them drawn with multiple cells and they'll look like this small big small big and small and positive negative this has 1 2 3 cells so that's battery next up the capacitor capacitors have the capacity to store an electrical charge in the circuit there's two types there's non polarized and there's polarized the non polarized type look like this two straight lines the polarized type have one straight line one curved line the straight line side is positive the curved line side is negative another important component is the diode the diode acts like a one-way valve electrons can flow in one direction but not in the other this is what the symbol for that looks like basically this would be the ground side right here that's the cathode the big line is the cathode on the diode itself that will be a line and that is the cathode side or the negative side a light emitting diode or an LED would look like this we have the same symbol as a diode but we'll have a couple of arrows pointing off from it indicating that it is emitting light now we'll move on to the transistor the transistor is really important because it can act like a switch or an amplifier in a circuit and it can work from positive or a negative signal this is what the symbol for a transistor looks like circle there's a line coming in to it a line in the middle two more lines and then there will be an arrow now this arrow is really important because this is what tells you if it's an NPN or a PNP transistor NPN means negative positive negative PNP means positive negative positive the arrows determine what that is this one with the arrow pointing out of the circle is an NPN a PNP transistor would look almost the same but I would have the arrow pointing in on this side now there is an emitter a base and a collector on a transistor where the arrow is that's always going to be in the emitter the other one the collector and the one that leads in here to this plate that's the base the base is what turns the transistor on and off switches are very common and they're important because they turn things on and off the symbol for that is actually quite simple it's just a line a dot a contact input output or input output it doesn't really matter which way things are connected this would be the part that closes across this gap and allows current to flow through the switch this is a normally open switch and it would be labeled simply in O now if it was a normally closed switch it would come across like that and be labeled in C robotics use a lot of motors a motor symbol looks like this just a circle with a great big M in the middle that's a motor if it's a stepper motor it will have a line under it that looks like this in an amplifier circuit you'll see the symbol for a speaker and it looks quite like a speaker actually this would be the magnet and this would be the driver that's a speaker sometimes you'll see two leads coming off marked positive and negative here's a very important symbol in a circuit the ground symbol that would be the negative side of the circuit or the whole ground plane that looks like this it looks a bit like an arrow how about a transformer no not the ones in the movies the ones that will transform voltage either stepped up or step down through induction those usually have an iron core and they look like this these two symbols simulate the iron core and these are the primary and secondary windings fuses help protect a circuit they're rated in amps as in how many amps they will carry before they actually melt and break the contact between each side there's a symbol for them that looks like this let's talk about some of the ratings of these components now resistors are expressed in ohms we already saw that but I'll draw it again this is the symbol for ohms capacitors are rated in farads or micro farad's most of the time the older way to do it was just simply m-f you don't see that too much anymore now you see it more as micro farad which is the symbol for micro and it looks like au with an F next to it sometimes you'll see P yeah and that is Pico farad's that's even smaller than a micro farad well that's about it a short and sweet primer on how to read schematics if you want to learn more do a google image search and type in schematic symbols you'll see all kinds of pictures and if you click through on some of them to the sites you'll learn more about how to read them and what all that stuff means at least now you have a basic understanding of how things hook up and I got a lot of questions on some of my schematics in the past where people are like where's the ground where is the negative connect to etc so now you've got a little bit of an idea of how to understand that so I encourage you to go out and learn more because there's always more to learn you never know at all so I hope you enjoyed that until next time another comport important

Channel: HackaweekTV

Views: 269,555

Keywords: electronics, resistor, capacitor, diode, transistor, transformer, ldr, potentiometer, battery, speaker, schematics, electrical, circuit, pcb. diy, Circuit Diagram, robot, motor

Id: TGMj5Yo67WY

Length: 12min 12sec (732 seconds)

Published: Sun Jan 26 2014