Other Experiments

Potato Battery

Apart from the modules, you will find a few other odds and ends in the toolbox. There are some zinc nails and a small length of copper tube. You can use these as electrodes for a potato/lemon battery. When you tried to make one of these in Cornwall, we were lacking some of these pieces so now you have them. The amount of power a potato can produce is quite small to getting it to light bulb probably wont work unless you use a lot of pototoes! You can now use the meter, which is much more sensitive to see if you are producing any voltage. You might even be able to use the LED but make sure it is the right way round, so check which 'terminal' on the potato is positive!

Electromagnets

If you wind lots of turns off wire into a coil, you can make an electromagnet. There is a bolt, a couple of nuts and two large washers in the toolbox. If you wind a coil onto the bolt, between the washers, you should be able to make a powerful electromagnet. The washers are simply stop the wire falling off the end. Start at one end (leaving enough wire spare for a connection) and wind the coils side-by-side along the length of the bolt. When you get to the end, wind back towards where you started, always winding in one direction (clockwise or anticlockwise). If you make the coils neat, you should be able to get a lot of wire on there, the more wire, the better the magnet. When you finish, hold the wire in place with some tape, then bare the two ends and connect them up to the batteries (via a switch if you like). Get a few paper clips or anything magnetic and turn it on. You should have a strong magnet you can turn on and off. This is exactly the same principle as those large magnetic cranes you see in car junk-yards, those electromagnets are so large, they can pick a car up with one.

You may find the bolt stays slightly magnetized after you turn the power off. This is because the bold is made from mild steel which has a kind of 'memory' to magnetism. If you used an iron bolt, then the magnetism would all but disappear as iron does not behave the same as steel. Getting an iron bolt is not so easy these days as steel is much stronger and who would want a weak iron bolt when you could have a stronger steel one ? Nevertheless, keep your eyes open and you may find one being thrown out one day.

Relays

You can use electromagnets for all sorts of things and they form the basis for buzzers, bells, motors, relays, generators magnetic levitation; you name it - electromagnets are in many electrical appliances. I mentioned relays so now seems a good time to explain how one works. A relay can be thought of like an electric switch. If the end of electromagnet brought near a steel switch, the magnetism can be used to move the switch and make a connection. And this is exactly what they do. Here are a couple of diagrams that show what I mean.

You are probably thinking 'hang-on, there is a normal switch in the coil circuit, so why not use that to switch the lamp on anyway'. In this example you are exactly right. But relays are made so that a small current is used to feed the electromagnet which can be used to turn on a big switch to control a large current. An example of this is in a car. When you start a car, it is possible to draw 200Amps of current. A switch to switch 200Amps would be like something out of a Frankenstien movie, and large sparks would occur. However, there is no Frankenstien switch in a car, only a small key. The small key switches a small current to a relay which then switches a large contact allowing 200Amps to the starter motor to start the car. That is why you often hear a 'click' as you start the car, that is the relay turning on and the internal switch moving. You will notice the distinctive 'click' in many electrical appliances, washing machines make lots of clicking noises as relays switch on valves and pumps as the wash program executes.

Using the Relay Module

Now you know all about relays, you will find there is a relay module in the toolbox which you can experiment with. Identify the coil terminals and power it us using the battery and switch. You should hear a click when the relay turns on. You can check what is happening on the relay terminals using the meter set to resistance. Once you have worked out which terminals are which, you can power a bulb so that it is switched on when the relay turns on. (or is always on until you turn the relay on if you want). Here is a photo of such a circuit. Try drawing a circuit diagram and then wiring it together.

And finally...

You can wire a relay up so it works like a buzzer. Relays are not really intended for that, but hey, why not? I leave that as a problem for you to try and solve. Hint: Remember that the relay's common terminal moves when the relay is powered up.

There are lots of things you can do with these simple modules. After connecting them with crocodile clips you may decide to use them for something more permanent and that is why there is wire in the tool box. And once you have mastered electrics, there is a whole world of electronics out there which can extend what you have done here to build even weirder contraptions. Hope you enjoy it.