These innocent little components are great fun and a bit of light relief after some of the other subjects we have looked at.
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.
At first glance this board looks very confusing but the fog will clear as we go through it. Move the toggle switch so it’s up. This is the position of the switch as it is marked on the board. You will see it connects the blue switch with the meters. That means these are connected to the positive side of the battery and the line/wire going to the bottom of the board is connected to the negative end of the battery. The first meter gives us the voltage and the second the flow of current through the circuit below. Follow the wire from the ammeter down to important part of the board where things are happening. On the left are the symbols for diodes (yellow and blue) pointing in different directions. Diodes only allow current to flow in the direction of the arrow. So, when you hold down the big blue button, the yellow light will turn on because the current can flow through that part of the circuit. The blue light isn’t on because the diode is stopping it. Now throw the Reverse Polarity switch so it’s in the down position, you will see the both meters swing the other way as the part of the circuit that was positive is now negative. See that the yellow light has turned off and the blue light is now on. Now flick the reverse polarity switch back to the up position.
We will now look at the next part of the circuit – this is four diodes in a diamond and is called a bridge rectifier, the idea is that regardless of whether the input to the diamond (the left and right corners of the diamond) are positive or negative, the output (the top and bottom corners) always has the positive at the top and the negative at the bottom.
As you flick the reverse polarity switch you will see which two diodes are allowing the flow on current. It will change with the polarity. The last two diodes (green and white) on the board have one diode in each direction, but because the polarity doesn’t change, the white on will never switch on.
All the lights hear are called LEDs. LED stands for light emitting diode, yes there are diodes so they will not allow the current to flow through the wrong way unlike a normal light bulb with doesn’t care. You can get diodes that don’t emit light, but we haven’t needed to use them here because the LEDs worked just as well.
This is why we must wire LEDs up the right way, if we wire then the wrong way, they will not work!