How to Use Relays with Arduino

welcome back to the MasterTech and in today's video I'm going to show you how to control a high voltage AC device from a low voltage DC signal coming from a microcontroller like an Arduino and we're going to achieve this using a pretty simple beautiful electrical component known as a [Music] relay so we're going to keep today's video pretty short and focused on uh the concept at hand on the relay because uh a lot of the bigger uh Better Batter Arduino projects that we're going to be doing soon on the channel we'll rely heavily on using relays to control the higher voltage components and also because my garage is still chaos and not set up for building bigger projects just yet so the 3D printer is still getting hooked up the CNC is getting hooked up my desks are getting hooked up we're unpacking bins and boxes so let's stay pretty focused on this video now obviously I love Arduino projects I think anyone with a interest in hobby electronics can have a ton of fun building with Arduino Raspberry Pi and other commercially available microcontrollers um however these devices are all pretty much limited by the fact that they can only Power low voltage DC outputs without using some sort of switching mechanism but there are so many things you might want to control that are much higher voltage than this and uh ac voltage even so like way higher and not even DC voltage but basically the solution to controlling really high voltage things with really low voltage things is a uh electrical component known as a relay and now relays are always going to have two voltages uh two measurements with regard to uh how they're rated that you need to know um one of them is going to be the voltage at which they switch because they make relays for kind of almost every level of voltage so uh to control something from an Arduino which is capable of outputting kind of at most 5 volts you need a 5volt relay or you need uh a board kind of like I have here that's capable of taking 5volt signals from an Arduino and then uh it needs a 12volt power supply on it because these are 12vt re relays um so I'll show a better image of my 5vt relay on the screen now and I'll link some of these products below if you need relays for your project um but basically the first measurement is what voltage the relay gets Switched at so for uh like I said for just an Arduino application you want that switching voltage to be at about 5 volts or you need a power supply and a switching mechanism to go bigger than that and the second measurement that all relays have is a maximum voltage and current that it can tolerate on the downstream side on the side being switched so there are basically two completely independent electrical connections that get made in a relay one is the one that you actuate and the other one is the one getting switched the one getting switched will give you a maximum voltage and a maximum current and it obviously it doesn't care if less voltage and less current um than that go through but that is how much it's electrically rated to be able to handle so for example a relay that says 10 amps 250 volts on it does not mean you have to put a 10 amp 250 volt circuit through through it it just means don't use more than that much voltage and current um on that don't use that more than that voltage or current it's rated for either of those two maximums not both of those two maximums now for DC relays most relays follow a pretty standard convention where they have three pins one of those gets ground one of those gets the uh switching voltage so 5 volts 12 volts whatever for the Arduino one it's 5 volts and then the third pin is your signal wire so that is the one that you hook up to an Arduino digital digital output or even a push button if you're going to make it just simple relay logic instead of using a controller um that third signal that third terminal is the signal wire which is what you actually switch to switch the relay on and off and then the downstream side of your relay which is being switched will also have three terminals but most of the time for most applications you only need two the reason for three terminals is it gives you the option of connecting your device as normally open or normally closed one of those terminals is the common meaning you bring in the wire that you want to sometimes make contact to your Downstream wire sometimes break into the common terminal and if you want the device to be running until you send the signal then you want the normally closed terminal block because that means when no voltage is being provided to the relay it is making contact with the normally closed side of your relay but if you want the device to turn on when you turn the output on which is probably more common for jav electronics um then you're actually going to want to uh put it on the normally open side because that means when no vol is being sent it is open and then when you do send voltage uh it gets broken that chain gets broken so that's the difference between normally open normally closed if you have questions about that let me know in the comments below but normally open and normally closed are super common Concepts in electronics controls and automation uh robotics anything like that so it's good to familiarize yourself with those terms and it's super important to reiterate this uh you don't hook 120 power and neutral up to two terminals on the high voltage side of the relay you let one of those wires go inter uninterrupted straight to your device just like it would if there was no relay you're only interrupting one signal wire uh if you put one 120 on the common and a neutral wire on normally open or normally closed then you're going to create a dangerous uh AC short on that relay at some point you don't want to do that um you want to interrupt like your neutral line of AC power by putting the side closer to the plug to the wall outlet on the common and then the downstream side that will actually connect uh and close the loop of power for your device on normally open or normally closed so hopefully I've created a super useful graphic on the screen right now that illustrates that do not create an AC short and this is a good opportunity for a general disclaimer don't do any work with high voltage or ac voltage uh unless you're super comfortable with basic electrical components if you are a child or a younger person um consider grabbing an adult or watching a whole bunch more videos on how to safely work with ac voltage because um 120 230 not usually lethal but totally a short is capable of starting a fire causing a ton of harm so be super duper careful with anything considered higher voltage than like 20 volts DC and even then you could do some damage so just be generally careful with electricity and to be honest for this video I think writing any Arduino code together would actually be over complicating the tutorial that I'm trying to do here because you control this relay like you control any other output from any Arduino at any point and if you really need help going all the way back to those basics of how to control and output using Arduino I will uh drop a link to my Arduino beginner tutorial series on the channel cuz we use tons of LEDs and motors and push buttons and other sorts of inputs and outputs so if you need a total Basics refresher um you can watch those videos but in general you turn a digital output on from your Arduino and you're going to activate the relay you turn it off and you'll turn the relay back off you can simulate this even just by connecting the signal wire to 5 Vols and then removing it from 5 volts you should physically hear the relay connecting you most relays have an LED indicating when they're on and off so I'm not going to write any code with you if you have questions about the code just go ahead and ask them in the question uh comments below but that is going to do it for this video I hope you found it useful I hope this was what you were looking for when you clicked on this video as always let me know if any comments in the uh comments below questions in the comments below let me know what project you'd like to see next on the channel in the comments below a massive thank you as always to my patreon supporters thank you everyone who's a regular fan of the channel for sticking with me through the holiday season obviously didn't roll out a ton of content around the new year um traveling for family uh dealing with a baby moving into a new house so I appreciate everyone uh sticking around we're going to do a lot of cool things in 2024 thank you so much for watching good luck with your projects see you next time bye