Lesson video

Hi, my name's Mr. Brown and welcome to this lesson on push-to-make switches.

Quite a lot to get through today, so I hope you're ready.

Hope you've got your design brains ready.

And we'll continue with today's lesson by thinking first about the learning cycles, the keywords and the key learning outcome.

So our learning outcome today is to make a push-to-make switch.

Here are the keywords.

The keywords are: series circuit, that's a loop of connected electrical components, a zinc-carbon cell, that's a component that makes electricity using a chemical reaction, a push-to-make switch, that controls a circuit by pushing the connection together.

And here's the lesson outline.

So with this lesson on push-to-make switches, we are going to be looking at push-to-make switches in safe circuits.

And then we're gonna be looking at push-to-make switch and how to make it.

And of course we're gonna start off by finding out about how to make push-to-make switches and how to put them into safe circuits.

First of all, let's talk about what a series circuit is.

Now, a series circuit are where components are connected together in a loop and the electricity from the cells power the series circuit.

And if you look at that diagram there, you can see the cells and you can see how they are in a loop.

This series circuit has got two AA cells in that battery pack and these are zinc-carbon cells.

And we use those rather than alkaline and rechargeable cells because they can, they're less likely to short circuit and they're less likely to get hot.

And so they're a bit safer to use in the classroom.

Let's talk about cells and battery safety.

So they're used in schools 'cause they're less likely to short circuit or get hot as I said in the last slide.

But if the cells do look damaged, you must tell the teacher and don't touch them.

You need to keep water away from circuits and from the cells.

That's a really important life lesson, that water and electricity should not mix.

You need to connect the battery packs last when making the circuit and disconnect them first when you're finished.

That means there's less likely to go wrong with the electricity if the electricity isn't actually connected.

And lastly, always follow the teacher instructions carefully.

Check for understanding now.

Which of these circuits will work? Is it A, B, or C? Which one will make sure that the light bulb lights up? That's right, well done.

It is C.

And you can see there, there is a loop there from the cell to the light.

Whereas with A, both of them, both the wires, both the crocodile clips are connected to one side of the battery.

It needs to be both sides to ensure that the polarity works.

And in B, you can see that the connections are not fully made either.

So when we are talking about an electrical series circuit, it could contain all sorts of different components.

So it might have a bulb in a holder, a battery pack, battery pack with zinc-carbon cells.

It might have a motor, this one's a three to six volt, or a smaller one, which is 1.

5 to three volt.

There's a buzzer, some leads and an LED.

Now switches that are in an electrical circuit are a type of input, and that means that because they're an input, they actually change the circuit.

Now we always think of an input as maybe something turning something on after having the light sensors going down or they hear a sound and then it makes a change.

But actually just pushing a button or having a switch, that is a type of input because it has an effect on the actual circuit.

Switches can connect or create a break in a circuit, which is, that's a type of control.

And switches also activate a signal.

So for example, they could set off an alarm.

One type of switch that can be used in a series circuit is a push-to-make switch.

We're gonna talk about what that is now.

Now museums often instal alarm systems to protect their valuable artefacts.

Now some of these alarms could be pressure pads which are a form of push-to-make switches.

Now there's a circuit diagram example here and there you have a disconnected switch, a disconnected push-to-make switch.

And the push switch, the actual switch there by this diagram form is actually those lines, if you imagine that being a button to press.

And the two circles, well, those are the two connections to the actual circuit and that'll make sense in a moment when you see what it looks like when it is connected.

So the pressure is pushed down on the button and there we have the connected circuit and you can probably see now how those lines have actually been pushed on top of the circles and that has created a completed circuit.

In this regard, then an alarm might sound so the switch will send a signal to whether it be the buzzer or a micro:bit or whatever it is to sound an alarm.

So when we talk about this as being a circuit diagram, a circuit diagram is a simple drawing showing how electrical components are connected.

So in this series diagram you can see very, very simple symbols just to represent some of the more complicated components we're using.

And the reason why it's simple is that it makes it easy for anyone to understand.

Now remember that the lines don't represent the actual size or the distance between the components, but they're spread out equally.

Just makes it nice and simple.

So here's some circuit symbols for you.

Because every electrical component has a different symbol.

And today we are going to be looking at AA cells.

So there's two AA cells there.

You can see a bulb and also a push-to-make switch.

Let's go through those again, see if you can recognise which one is the push-to-make switch.

So this is your check for understanding.

Which of these is a push-to-make switch? A, B, or C? That's right, well done.

It is B.

Swapped them over a little bit, just to see if you would still get it.

I'm sure you did.

And that is the, the middle one there is the push-to-make switch.

One on the left is the two AA cells and the one on the right is the bulb.

So here's your first task.

So I'd like you to draw a circuit diagram now yourself.

So using a ruler and a sharp pencil, remember we want nice clean lines here.

Can you draw an electrical circuit with two AA cells with a bulb and a push-to-make switch? Should be a nice simple way of doing this.

Don't make it complicated, make it nice and simple.

So include those three components within your circuit diagram.

Right, welcome back.

I'm sure you've done a really good job of drawing this really neatly and thought very careful about the simplicity of how you've done this circuit diagram.

Now we do tend to have the cells at the top but it can move around.

But often you'll see circuit diagrams with the cells at the top.

Here you can see that Sofia's drawn her circuit diagram linking the two cells and the bulb and the push-to-make switch as well.

Okay, onto lesson cycle two.

So we're gonna make a push-to-make switch now.

Now there's different ways of doing this and I've come up with two ways to show to you today.

So the first one is split pins and the other one is using aluminium foil.

Now as you can see there, the two different ways.

What we're doing is we're using the conductor, so using the metal to connect the circuit.

The one on the left using split pins, there'll be wires attached to the other side of the split pins.

And what happens is, as that piece of card is pushed down, it pushes the two split pins together and that connects the circuit, very similarly with using aluminium foil.

There will be foil on the back of these switches and then as they are pushed down, the foil conducts the electricity and the electricity flows through and that connects the circuit.

We'll go through step-by-step instructions about how to use those in a moment.

Check for understanding then.

We talked about push-to-make switches but which of these is not a push-to-make switch? Have a look.

Is it A, B or C? That's right.

Well done.

It is A.

A is not a push-to-make switch.

It's often what we call a push-to-break because we push that away to actually create something as we actually push things together to actually make that switch.

So resources that we're going to need today for push-to-make switches: we might need scissors, pencil, sticky tack, circuit components, split pins, aluminium foil and card.

Now these are things you may or may not need.

The pencil and the sticky tack is more for creating holes in the card.

Scissors obviously to make cuts with the foil or with the card.

And then we've got the circuit components there.

Now for this example we've chosen a buzzer but there are other circuit components that you could use if you wanted to.

So how to make a push-to-make switch using split pins.

So first of all we need to make holes in the card for the split pins, and then we put the split pins through and we fold the card in half.

Now this is really important that when you fold it in half, the split pins must touch, so the heads of the split pins must touch.

We then fold out the split pins on the back so that they don't touch.

It's really important that those node ones don't touch.

And then you attach the circuit to the split pins and then test it.

And you can see there on the furthest right picture, you've got these split pins being attached to the circuit using the bits where it's actually split, and then the heads of the split pins, they push together to connect the circuit.

Now, working with aluminium foil.

It is quite similar in a lot of regards but we'll go through it step by step.

So you need to cut two small pieces of aluminium foil, you then need to fold each piece of foil over the card.

You then need to fold the aluminium foil inside so you can see that it's covered on the front and the back.

And then you attach the circuit and test the switch.

And as you can see there, we attach the push-to-make switch with an aluminium foil with the crocodile clips just for this prototype and put one onto the top, one onto the bottom.

And then of course when they press together, and when they push to make the circuit, then that creates the circuit components to work.

And in this example, the buzzer will come on.

Check for understanding.

Which of these can be used for making a push-to-make switch? Is it A: aluminium foil, B: art straws, C: split pins, or D: elastic bands? So which of these can be used for making a push-to-make switch? Now be very careful 'cause there is actually more than one answer here.

So aluminium foil, art straws, split pins or elastic bands? Off you go.

That's correct, well done.

It's aluminium foil and split pins.

Okay, so let's talk about the buzzers now.

Now the buzzers have red and black wires and it's really important that we think about why they've got red and black wires, because for the buzzer to work, the wires have to be the correct way round.

If they are not the right way round, then what will happen is it just won't work.

And sometimes people get really, can get quite frustrated because they think they've got the whole circuit correct and yet it actually isn't correct because the buzzer is just needs to be switched around.

So they might have done everything right, except they haven't got the wires the correct way round.

So if you have a look, there's a series circuit not working and there is a series circuit working.

Now you might ask, well I can't see much difference.

Well actually if you look very, very closely, you'll be able to see on the left hand picture, you've got the red wire and then the black wire.

So the red wire is on the left and the black wire is on the right coming straight from the buzzer.

If you look on the right hand side, you'll notice that the black wire is on the left and the red wire is on the right and that means it's actually working.

And this is just a tiny minute thing like that can, we need to make sure we recognise that buzzers only work one way round and that's to do with what we call the polarity and that's making sure that the positives and the negatives are the right way round with regards to the cells and for the buzzers as well.

And we won't go into the science of that, but it's really important that we do understand if the buzzers don't work, this might be a reason why.

So very, very simply, if it doesn't work, swap the wires over.

Okay, so now it's time for you to actually have a go.

And I would like you to make a push-to-make switch using one of the methods that we've talked about today and connect it to a series circuit with a buzzer.

So you could either use the split pin method or the aluminium foil.

Now let's go through, you can go back to the slides which show you exactly how to actually make the split pin switch or how to make the aluminium foil switch.

It's really important that you have a look back and make sure that you understand how that is.

But let's go through it very, very carefully again.

With the split pins, you need to make sure the heads of the split pins meet when the piece of card is closed.

You need to make sure that you are making the holes for the split pins really carefully and using sticky tack and the pencils is a really good way of making safe holes.

And then you need to attach them to a series circuit with a buzzer.

I mean we've said buzzer, but of course you could use other things if you wanted to.

If you wanted to use a light bulb.

It depends upon the resources that your school has got available.

Now with the aluminium foil, very, very similarly, you've got that piece of card that's gonna be folded in half and then we're gonna cover two ends with the aluminium foil.

Remember, we don't want to cover the whole piece of card in aluminium foil because that won't work.

It will just be constantly connected and there won't be any break in the circuit.

So that's really important that you make sure that there isn't a break in the circuit, sorry, that there is a break in the circuit and it's not just a continuous loop because aluminium foil is that conductor.

So then we need to attach it possibly using crocodile clips or wires, whatever your score has got available.

And then you're going to connect it to a component to work.

And then you should be able to find that you are making a pressure switch or what we are calling today a push-to-make switch.

Okay, it's time for me to let you get on with it now.

So you need to go and make a push-to-make switch using either split pins or with aluminium foil.

Remember, before we go, that if the buzzer doesn't work, swap the red and black wires around.

It's really important that we remember from the previous slide that if the buzzer doesn't work, swap the red and black wires around.

Okay, I'm gonna let you get on now.

I'm sure you're ready.

Sure you've got all the knowledge ready and enjoy this task.

Be safe, remember to go through the safety measures that we talked about and enjoy this task.

Okay, off you go, Right, welcome back.

Let's go through a bit of feedback.

So Aisha made a push-to-make switch and she connected it to her simple series circuit to test it.

And you can see there, there's the button going down.

Obviously the GIF doesn't have any sound, but you can see, remember we talked about those diagrams earlier where the black wire was on the left and the red wire was on the right.

And there you can see that, that she's connected it properly and she can say that the buzzer sounded when the push-to-make switch connected the circuit and sent a signal.

So the switch sends a signal through the circuit to make the buzzer sound and make the alarm go off.

Right, well done today.

I'm sure you've learned huge amount and you know exactly now how to make a push, what a push-to-make switch is and how to make a push-to-make switch as well.

And I think you can see how you'd incorporate this within lots of different types of electrical work, electrical circuits, and also with practical design and technology tasks involving electricity as well.

Let's go through the summary now.

So a push-to-make switch connects the circuit when it is pressed and completes the circuit.

Switches can be used in a museum alarm.

Switches can activate a signal.

And a push-to-make switch can be made using cardboard, split pins and aluminium foil.

Great, you've worked really well today, well done.

And you've learned all of this knowledge here, all of these key learning points and I look forward to working with you next time when we talk about all different sorts of things, possibly to do with more switches, possibly to do with utilising these switches within products.

But regardless, I look forward to working with you next time and I'm really pleased that you've been with me today for this lesson.

Thank you very much and have a good day.