# Beginner Electronics - Beginner Electronics – 23 – Relay Oscillator & Speaker

## Beginner Electronics

29 Lessons

### Beginner Electronics – 23 – Relay Oscillator & Speaker

what is going on everyone my name is Kota Moore and welcome back to electronics episode 23 in this episode we will be using relays and capacitors

to design an oscillating circuit which we can connect to a speaker to make sound or an LED to make it blink by an oscillating circuit I mean a circuit that is able to automatically switch

between an on state and an off state essentially think of a blinking light that's what we're going to be creating today so we'll create a device that has an output that is off for a certain

amount of time turns on for a certain amount of time off again on again off again now there are countless ways to create an oscillating circuit of course but in my opinion the absolute simplest

form of an oscillating circuit that can be created is a relay oscillator now of course because it is so simple it is not the best oscillator at all and in fact it's very very important unstable but

that's okay because in the next tutorial we are going to get into integrated circuits and we are going to make an even better oscillator and in fact our 8-bit computer is going to need an

oscillating circuit so we should probably learn about them now I am going to warn you that this relay oscillating circuit does have a possibility of damaging a relay now if you use a high

enough capacitance value your relay should be able to handle it but I would just be very careful follow the schematic that we're going to create very carefully and don't connect the

power until you're completely done putting everything together on the breadboard but hey if you do break a relase that's okay because failing means you are learning anyways let's go ahead

and design this relay oscillator of course I have a relay right here this is a double pole double throw relay which we will be using and I'm actually going to begin by drawing a battery in here of

course right next to this here's the positive terminal of the battery and we are just going to hook that right on up to one of the terminals of the electromagnet of the relay and we'll

hook up the negative terminal to one of the terminals of the actual switching part of the relay and it is important that we connect it to one of the terminals that are default ly connected

together here so when the electromagnet is not the Empowered these two terminals are being connected together but when we do power the electromagnet then these two terminals are going to get powered

together so because these two terminals are connected together when the relay is not being powered we're actually going to hook up this other terminal to the other end of the electromagnet now let's

stop right here and take a look at this really quick basically what we have is positive power running to the coil or the electromagnet at all time and when we first took this

circuit up we will have electricity traveling through it will be able to travel through the switching part of the relay to the coil and the electromagnet will power up but when the electromagnet

powers up this switch part here switches and these two terminals become connected while these two become disconnected so that means power will try to flow but it won't be able to flow to the

electromagnet anymore that means the electromagnet is going through power off and the switching state is going to reset and these two will become connected again and when

that happens of course electricity now has a path again to the electromagnet and it'll turn on again so it will oscillate turn on and off very very rapidly but this would most likely

damage your relay and we really don't want to do that and we also don't want to circuit that oscillates back and forth dispatch for our purposes so to slow this oscillating circuit down we

are going to throw in a capacitor and we're going to throw it in on the terminals of the electromagnet here so we're actually going to hook that up I'm going to be using the electrolytic

capacitor so we'll draw that schematic symbol in right here remember this is the positive side of that capacitor so what this does is when power begins to run through it'll also charge up this

capacitor that way when the switching part switches to not supplying power the capacitor will actually be able to power on this coil for a short amount of time and once the capacitor runs out of

charge then it will flip back to its state and be able to power the electromagnet and charge up the capacitor again so the capacitor will slow down our oscillation so that is

actually our oscillator right here now of course we need to hook this up to something and to do that we are going to use this other part of the switching part of the relay here what I'm going to

do is I'm going to take the negative terminal of the battery and I'm just going to loop that around to the common terminal of this switching part and I'm going to hook up the other terminal down

here and I'll take the positive terminal down here now you can hook these two wires up to anything you can hook up a resistor and an LED to have a blink on and off or really anything that you just

want to turn on and off over and over again but LEDs are kind of boring at this point in the series so let's try something new let me draw in this schematic symbol

right here and of course the schematic does have a positive and a negative terminal now what in the world can this be well of course it is a speaker so if we hook up a speaker to this oscillating

circuit it will actually begin to make noise because we will be turning it on and off at a fairly rapid rate now it's not going to be any really fancy noise or anything but hey it will be some

noise and just so I am able to actually control the noise that comes out of the speaker unknown can take part of this wire away right here and I'm going to add in a switch that we can turn on and

off instead this way we can turn the speaker on and off with the flip of a switch so real quickly again we have power always going to the electromagnet and to the positive side of the

capacitor and initially we will have a path for electricity to travel through the electromagnet and to charge up the capacitor and once you electromagnet has enough power to turn on then these

switches will turn onto these two terminals here electricity will not be able to travel to the electromagnet anymore however the capacitor will be able to

provide electricity to the electromagnet so that it stays in that position for just a little bit that way we slow down our oscillation once it runs out however the electromagnet will turn off again in

these two terminals will become connected and electricity has a place to travel again and also recharge the capacitor so let's go ahead and get to making this oscillating circuit here now

I will be using a five volt power supply for this so you have to make sure that the speaker that you are using is able to operate under that voltage mine is able to but if you don't have a speaker

that can do that then of course you can just use an led into resistor and have that blink instead and of course my speaker here has a positive and a negative terminal that I'm going to use

alligator clips that hook up to eventually now I'm going to be using the same relay that I used in the last video here of course the far too right pins are for the electromagnet the right pin

and the center pin here are connected together by default and the right and left pin is connected when the electromagnet is running so I'm just going to go ahead and put that in the

breadboard here like so and I'm going to first took up one terminal of the electromagnet to the pause terminal or the positive power rail of my breadboard and I'm going to begin by

using a 1000 micro farad capacitor now I highly recommend that you use the highest value capacitor that you have this way you're not going to burn out your relay just in case it does happen

and also if you use too small of a value of a capacitor the speaker might not be audible and remember that electrolytic capacitors are polarized so you do have to make sure that you connect the side

with the stripe of negative signs to the more negative side of your relay so I'm going to go ahead and put that in remember if the anode is going towards the side that is connected to positive

already and the cathode is going to the other side of the electromagnet of my relay here now I'm going to go ahead and remove my relay so I'm just taking a look at where the pins line up this way

I'm able to build the circuit easier and I'll start by connecting the electromagnet the more negative side on over to the common terminal of my relay and as you can see that lines up there

so now I'm going to go ahead take a wire to the initially connected terminal and hook that up to one side of my switch and then I'll take the other terminal of the switch and hook that right on up to

the negative power rail so when it's on it will provide that negative power just like we had in our circuit to the electromagnet and now I'm going to put the relay back in here and if we go

ahead and push the button or rather flip your switch to the on position we should have a working oscillating circuit which I'm going to do right here and that sound is actually the electromagnet

within the relay moving around that's the only sound that it's making now I'm going to hook up a wire to the positive power rail of the breadboard and another wire to the opposite side of my relay

the other side of the switches and I'm actually going to hook these two wires up to my speaker and I'm also putting another wire here to the common terminal of that switch going right to the

negative power rail of my breadboard now I'm going to go ahead and take some alligator clips and hook them up to these two wires here and when I do that I'm going to take the more positive side

up for my speaker and hook that up to this wire here and the more negative side of my speaker up to this wire here because negative will be traveling through the relay like so

so let me go ahead and actually hook these up to the speaker I have my speaker has the terminals labeled plus and minus so I'm just going to hook these up and now what should happen is

if I flip on this circuit we should have a series of audible clicks from the speaker enough in here that is actually happening and we can clearly hear that speaker making a bunch of noise here so

that means our circuit is working now let's try something a little bit different I'm going to take this 1000 microfarad capacitor and replace it with a 470 micro farad capacitor I'm going to

hook it up in the exact same way now I am decreasing the amount of capacitance so what should happen is my speaker or rather my oscillating circuit actually should actually increase its speed and

therefore we should have a more speedy audible sound we're actually going to have a higher frequency and as you can hear and as you can hear that frequency is definitely much much faster so you

can experiment around with this play around with it have some fun and I'll see you guys in the next video where we're going to work on integrated circuits and make a much better

oscillating circuit that we will actually end up using in our 8-bit computer thanks for watching everyone and I'll see you then

Today we make the simplest form of an oscillator to allow a speaker to make noise!

See my website: https://codenmore.github.io/