All About Brushless DC Motors And Generators

[Music] hi so brushless dc motors they're absolutely everywhere as it happens you find them in printers if you've ever been tempted to buy one of those backpacking things or those micro generator wind turbines that's going to be a brushless dc motor only used in reverse because basically if you have a coil of wire and a magnet you can make a motor or a generator if you stick some current in there it's going to move if you move it it's going to give some current out when it's arranged as a coil or a magnet it's either going to be a generator or a motor depending on how you use it and you can use it either way and that's really really useful now the thing about brushless motors obviously is they're incredibly robust and cheap to make i mean they don't have any brushes so there's very little to wear out apart from the bearings and they just go on and on and on and their output is actually quite respectable so this is from a printer it's actually about the size you would find in a generator now if we take the top off of these and we're going to do that and have a close-up what we'll really see is just a ring magnet and some coils that's all there is and then some control electronics now there are in two ways of wiring this one looks like this and you'll notice it's incredibly like a y and so it's called the y configuration those three coils are joined at a center point now when you look at your motor when you've got a brushless dc motor you'll either see three spots or four spots of solar where the wires to the coils go if there's four spots then as you saw in that diagram that's a wide configured brushless dc motor now there is another one that's like a triangle and the coils look like this now the greek letter with a triangle is called the delta so that's the delta configuration and you'll notice there are only three junctions in the delta configuration so if you spot your brushless motor has only three spots of solder on it it's likely to be delta if it's got four spots it's y configured what you need to do is identify the one where there's lots of wires in one spot of solder and then promptly ignore it which is great and then after that you proceed exactly the same way now if you have a brushless dc motor and you want to run it then you can use the control electronics so you can build your own control electronics so you can be really really cheap and buy one of these it's called an electronic speed controller now i bought this because it was three pounds on ebay and there's no way i could make that for that kind of price so i bought this and this will do 20 amps or something crazy so really cheap to buy an electronic speed controller the other thing you need is a servo tester to change the speed when you want to rotate a motor then what you need to do is rotate the magnetic field if you rotate the magnetic field while another fixed magnet is there which is what brushless dc motors are they're a fixed magnet in a rotating magnetic field what you need to do is pump some electricity in each coil in sequence so we have three coils you put a little bit of electricity in coil one and it creates a magnetic field it gives a magnet a kick the permanent magnet it'll just go to its little position of least um energy and just stay there if you then turn off that current you're supplying to coil one and supply to coil two it'll kick it some more do the same thing off with two on with three it'll kick it some more and you keep doing that in sequence you are creating a rotating magnetic field within those coils and that magnet will spin and of course that means your motor will spin so the electronic controller what it does is times the sequence of the off and the on to the coils in order to create a rotating magnetic field like i say you can do that yourself it's just such a lot of trouble to do it when it comes readily packaged so cheaply but it can be done quite easily yourselves but what we're going to do is we're going to use an electronic speed controller and we're going to set these motors up to run from the electronic speed controller so let's have a closer look at them let's start with this one this is the motor from cd-rom drive if you want to know how to get one of these out i've done some stuff on cd-rom drive videos where i just show exactly how to get this out this isn't attached on particularly well it actually just pulls straight off and if you'll see in there is a ring magnet that's the permanent magnet that the electrical rotating field acts against here we've got our little star shape and that's where the coils are now i look on that and i can see one two three spots of solder telling me that this is a delta configuration so i don't have to try and identify which one is the y but like say if you want to see which one is the y it'll be the one with three wires coming to it this one we've only got three spots on it so we we know which one this is now if we sold the three wires to there and connect them to this we can get that motor to spin which is exactly what we're going to do when we look at the pc fan we have exactly the same thing there are the coils there is the permanent magnet that they act against and if we take that off which i can't do we'll see the spots of solder this is the printer the printer one's actually really good because you can see the spots right there so we can just solder to those and we'll be able to run that as a motor so the first thing we're going to do is run these motors then we're going to have a look at how to turn them into generators so we're going to use this as a printer motor we're going to use this because we've got these three nice spots there that are really easy to get to so let's use it we've got a whole bunch of electronics around here which had to do with position sensing that kind of thing we don't need any of that in fact that'll get in the way because we're going to use that so the first thing to do is just to strip all of those off okay and here's our printer motor stripped off the electronics soldered on the three wires it's got a driver here so we pop it in there and give that a twiddle and there we go running the printer motor so as i say they're all pretty much the same thing just identify those wires that you're interested in solder an extension to them use one of these cheap controllers servo tester and you're away you can run just about any brushless dc motor okay so we've done the cd-rom motor but it's exactly the same for every single brushless motor you're going to come across i've soldered a wire to each of the three important wires all i have to do is put that case back on just make sure it's not catching i've attached it here to the electronic speed controller it really doesn't matter which order you put so each of these output wires is going to one of the input wires i've got it on a power supply here at six volts and i've got a servo tester on it so that i can test it there we go running a brushless motor it's a piece of cake okay so that's pretty easy and a bit of fun the other side of it like i say is generation quite often you want to turn these into generators and for good reason they're quite good generators now it actually emulates three phases so what we do with it is a three-phase rectifier now a three-phase rectifier looks like this if you're unsure about things like rectification and doing the circuits have a look at the video all about stepper motors i'd go into a bit more depth there but basically we need to grab some diodes and arrange them like that drawing now the diodes we can use are a whole range of things actually lots of people recommend lots of different things i tend to go for whatever i've got lying around or what's the cheapest stop just what works for me it means i use an awful lot of one and four double of sevens although i'm always told to use something else it matters if you've got a very heavy voltage drop uh you're not getting much output and the forward drop is gonna have a large impact otherwise to be honest if i get anything out especially of scrap i'm usually very happy so we're going to just use bog standard one four double or seven so we're gonna make a three phase rectifier bridge and then we're gonna test its output okay so to make the rectifier circuit you need six diodes you take two three sets of two and you put the silver to the black give it a twist and repeat that for the other two silver to black when you've done that you'll end up with something looking like this where each wire has two diodes at the end one with the silver line and one with the black line you take all of the blacks and twist them together and in that little mix put a black wire because these ones are your dc negative out okay that's it done we're now ready to give it a spin and see what we get out of it so these are obviously positive dc negative dc and it's really easy to know because it's the black end to the black wire negative silver end of the red wire positive and you deal with all brushless motors the same way okay there it is connected up to the voltmeter and we've got it on dc volt readings give it a spin not sure if you can see that there we go so we can get a couple of volts out of that easily enough so there you go brushless dc motors how to use them as motors and how to use them as generators it doesn't matter which way around they are whether the delta or y you just follow the same procedures identify the entire coils solder them onto a three-phase bridge rectifier and get your output or solder them onto a electronic speed controller and spin them up as a motor anyway i hope that was of interest thank you very much for watching and please do subscribe

Channel: Robert Murray-Smith

Views: 18,613

Keywords: motors, brushless, dc, generators, robert, fwg, murray-smith, engineering, design, technology, science, fair, project, stem, steam, how to, energy, power, generation

Id: _ST64RdesrU

Length: 10min 54sec (654 seconds)

Published: Sat Aug 15 2020