Saturday 24 March 2012
MAKING AN ELECTRICAL GENERATOR
MAKING AN ELECTRICAL GENERATOR
The very simple generator described below is primitive but shows the basic operation. It has been deliberately left as simple as possible so that there is maximum scope for using it in imaginative designs and inventions. It can therefore form the basis for a more complex device as shown a little further on.
The generator is made from a coil of wire (about 1000 turns) wound around the last 3 cm, or so, of a large nail. When a spining magnet is placed near to the device it induces a voltage into the coil and this can then be used to light a bulb (or better still an LED see end for details) - generation of electricity can therefore be simply demonstrated.
Diagram of simple generator
Step 1
Make up two cardboard circles about 3cm in diameter (1-2 mm thick). Carefully pierce a hole in the middle of the circles. Find a large (10-15 cm long, 6 mm wide) clean (unrusty) nail having a large head. Thread one of the circles onto the nail and push right up to the head.
Make up two cardboard circles about 3cm in diameter (1-2 mm thick). Carefully pierce a hole in the middle of the circles. Find a large (10-15 cm long, 6 mm wide) clean (unrusty) nail having a large head. Thread one of the circles onto the nail and push right up to the head.
Step 2
Cover the last 3-4 cm of the nail with a single layer of insulation tape (leave the nail head uncovered). Push the second circle onto the nail but only so far as the insulation tape. Add more tape onto the other side of the circle to fix the circle in place. You should now have a ready made 'spool' on which to wind the coil.
Cover the last 3-4 cm of the nail with a single layer of insulation tape (leave the nail head uncovered). Push the second circle onto the nail but only so far as the insulation tape. Add more tape onto the other side of the circle to fix the circle in place. You should now have a ready made 'spool' on which to wind the coil.
Step 3
Obtain some thin insulated copper wire (say 25m or so of 30SWG, aprox. 0.3mm diameter) leave about 20-30 cm free and start to wind turns onto the insulated part of the nail between the two circles. Wind 1000-1500 turns (the exact number does not matter much and will depending on how neat you can get them on before they spill over the restraining cardboard circles). Leave another 20-30 cm free at the end and then cut the wire. Tape up the whole assembly so that the wire does not come undone.
Obtain some thin insulated copper wire (say 25m or so of 30SWG, aprox. 0.3mm diameter) leave about 20-30 cm free and start to wind turns onto the insulated part of the nail between the two circles. Wind 1000-1500 turns (the exact number does not matter much and will depending on how neat you can get them on before they spill over the restraining cardboard circles). Leave another 20-30 cm free at the end and then cut the wire. Tape up the whole assembly so that the wire does not come undone.
Step 4
Take the free ends of the wires and scrape off the insulation. Wire them to a bulb or to an LED. Bring a magnet close to the head of the nail and while holding it about 5mm or so from the head rapidly move the magnet from side to side. The Bulb or LED will light showing generation of electricity !!
Take the free ends of the wires and scrape off the insulation. Wire them to a bulb or to an LED. Bring a magnet close to the head of the nail and while holding it about 5mm or so from the head rapidly move the magnet from side to side. The Bulb or LED will light showing generation of electricity !!
HOW A GENERATOR WORKS
A generator works by a magnetic field inducing a voltage into a coil of wire. Important points to note are that the voltage increases as the number of turns of wire on the coil, the size of the coil and the strength of the magnetic field increases. The magnetic field (or the coil) needs to be in constant motion to produce/induce the electricity into the coil. This can be done by moving the magnet or by moving the coil - the effect is the same. The coil (or the magnet) needs to move in such a way that the coil continually passes through the magnetic field.
The Iron nail is also important in our simple generator as it tends to concentrate the magnetic field. As the coil is wound around the nail it tends to draw in more magnetic flux into the area of the coil which boosts the overall efficency of the device and increases the voltage that is produced.
The type of wire in the coil is also important. For example, thick wire means there will be less power loss, but the down side is that the coil will get very large when a great number of turns is needed. In a practical generator some trade off has therefore to be found between the size of magnet, coil and the wire.
The Iron nail is also important in our simple generator as it tends to concentrate the magnetic field. As the coil is wound around the nail it tends to draw in more magnetic flux into the area of the coil which boosts the overall efficency of the device and increases the voltage that is produced.
The type of wire in the coil is also important. For example, thick wire means there will be less power loss, but the down side is that the coil will get very large when a great number of turns is needed. In a practical generator some trade off has therefore to be found between the size of magnet, coil and the wire.
AC or DC
This simple generator is called an AC generator. This means that the voltage appearing at the two wires alternates between + and -, and - and + each time the magnet makes a complete revolution. As a result the generator can light a bulb or an LED without you having to worry about which way round the connections need to go (as they are effectively reversing all the time anyway). However, this simple generator is not good for running radios, calculators or other devices that need a direct current (DC) that is produced for example from a battery. You can have fun though connecting up speakers to the generator output, as you can hear the electricity alternating - but please don't use your parents best Hi-Fi Speakers !, try using walkman type headphones etc.
This simple generator is called an AC generator. This means that the voltage appearing at the two wires alternates between + and -, and - and + each time the magnet makes a complete revolution. As a result the generator can light a bulb or an LED without you having to worry about which way round the connections need to go (as they are effectively reversing all the time anyway). However, this simple generator is not good for running radios, calculators or other devices that need a direct current (DC) that is produced for example from a battery. You can have fun though connecting up speakers to the generator output, as you can hear the electricity alternating - but please don't use your parents best Hi-Fi Speakers !, try using walkman type headphones etc.
A MORE ADVANCED GENERATOR
The photo below shows a simple hand cranked generator I built which used two of these nail-generators wired together (to give twice the power). This way both the N and S face of the magnet are used at once. One needs to get the wiring between the coils correct otherwise the voltage will cancel and you won't get any power from the gen! The coils are wired one after the other rather than one across the other (ie. a series circuit rather than in parallel). A simple wooden gear system was used so that you can comfortably generate electricity without having to turn the handle too fast.
A simple two nail generator with hand crank
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