WE02 - Switches

Youtube video, suitable whether of not you have the board with you.

See board images.

Tutorial guide for when you have the board with you.

Part 1

This board looks a bit crazy when you first look at it, but it will start to make sense as we go through it. Just above the battery there is a black rotary switch with a knob that can be turned. Move it round until it points to the line marked Parallel. Follow this line to the two red button switches, keep following the line past the switches and down the right side of the board, through the big green button switch and back to the battery. This is the first circuit. Now hold the big green button down and press one of those two red switches by the word parallel. The LED light above the battery should light up because you have completed the circuit. Note that it doesn’t matter which of the two switches you press because when they are wired in parallel the circuit will be complete if either switch is pressed.

Now turn the black knob round to the next position by the line labelled serial. This connects to the two switches in a different way - one after the other, we call this serial or in series. Now you will have to press both buttons (as well as the big green one) to get turn the light on.

Next move the rotary switch to the line marked 2-way. It connects the two toggle switches. With the way they are connected here you can use can use either switch to change the state of the light either from off to on or from on to off. So, we have two switches being able to control a light - very useful at home where you need lights at either end of a corridor for example.

Move the rotary switch to the last position and this time you can change the state of the light with any of the 3 toggle switches across the bottom of the board. Follow the lines you think are being used with the switches in their current position.

Part 2

The toggle switches use with the rotary at third position are not simple on-off switches. They have three connectors the one in the middle is always connected to one of the other two. Which one is connected can be changed when you throw the switch. This is known as a double throw or 2-way switch. The toggle switch in the middle at the bottom is more complicated because it has two of these switches build into it. This is called a double pole switch and as well as being a double throw, its full title is a Double Pole Double Throw or DPDT!

Some follow-up ideas to try...

• Try and find a location in a house where more than one switch controlled a single light. If it's two then you know that a 2-way switches must have been used. If its more than two then a cross-over switch will have been needed. A cross-over switch is somethings called an intermediate switch.
• A car has many switches, but think about the ignition switch and the horn, work out if you think these are wired in series or in parallel.
• Look inside a fridge and find the switch that turns the light on when the door is open. Very carefully try and turn the light off with the door open.