A dynamo, or electric current generator, is a device that converts other states of energy into electrical energy: thermal, mechanical, chemical. Bicycle generators that power headlights and taillights remain popular to this day.
Operating principle of an electric current generator
A dynamo generates electrical energy through the principle of electromagnetic induction. Typically, such a device converts mechanical influences directly into electrical impulses. It consists of a rotor (an open wire winding) and a stator in which the poles of the magnet are located. The rotor, without stopping its movement, rotates all the time in a force magnetic field, which inevitably leads to the generation of current in the winding.
The dynamo represents the following diagram of its device. A rotating conductor, or rotor, crosses a magnetic field and a current is generated in it. The ends of the rotor are connected to the ring (collector), through them and the pressure brushes the current moves into the electrical network.
Electric current in a dynamo
The resulting current in the conductor will have the greatest value provided that the rotor is located perpendicular to the magnetic lines. The greater the turn of the conductor, the less current will be. And vice versa. That is, the process of rotating a conductor in a magnetic field forces the generated electric current to change direction twice during one rotation of the rotor. Thanks to this property, this type of current began to be called alternating.
A dynamo for generating direct current is built on the same principle as for alternating current. The difference can only be noticed in the details, when the ends of the metal wire are not fixed to rings, but connected to half rings. Such half-rings are necessarily insulated from each other, which, when the conductor rotates, makes it possible to alternately contact one half-ring and then the other with the brush. This means that the generated current will flow into the brushes exclusively in one direction, in a word - the current will be constant.
How to assemble a dynamo?
A DIY dynamo can be assembled quickly. The basis for the future generator will be a wooden board about 30 mm thick and an area of 150 by 200 mm. The housing is attached to it with two screws so that the electromagnets are positioned horizontally, one against the other. Then, through the bearing attached to the housing, the armature axis is threaded, which is fixed in place between the electromagnets. Brushes are threaded through the inside of the bearing frame and the second end of the armature axis is inserted. The collector is fixed at this end.
Before attaching the bearing frame to the base, the armature must be aligned so that its rotation between the electromagnets does not touch them. The brushes should be located across the shoes of the electromagnets and secured to the bearing. A small pulley is attached to the free end of the rotor.
Electrical installation of the device consists of connecting the ends of the windings for electromagnets with brushes. Also, pieces of flexible wire are connected to them to communicate the device with an external circuit.
Generator and bicycle
A bicycle dynamo demonstrates its power depending on the rotation speed. For example, 
If the bicycle is not spinning fast enough or if it stops, the power to the light or other device will stop. But at high speeds, the light bulbs can burn out before their service life.
There are several types of bicycle electric generators:
The hub type is built into the wheel hub. Structurally, it consists of a static core on an axis and a reversing multi-pole magnet in the shape of a ring. Their cost is higher, which is offset by quiet operation and efficiency.
The bottle type is the most popular. The bottle-shaped device is equipped with a small wheel that is driven by friction against the sidewall of the rubber tire of the wheel.
The carriage generator is installed next to the carriage cup, below the frame stays. The movement of the spring-loaded roller is due to friction against the tire tread. It should be mentioned that the bottom bracket and bottle dynamo machine will stop working when exposed to wet conditions.
Channel Igor Kruch presented to your attention a new homemade product, which the author of the video made a long time ago, but all the time he could not film it and post it on YouTube. Finally a homemade big dynamo. The creation, which took about a month of work, was leisurely, thought out, everything was done with high quality, conscientiously.
Check out the selection of hand generators and neodymium magnets at this Chinese store.
It was made from what was available: a motor, a belt and a tensioner from an inkjet printer. In addition: a toggle switch, a lithium-ion battery 18650. A stiffening rib has been added. A pulley is made from disks. At idle, it produces a voltage of up to 11 volts and a current of 1.5 Amperes. There is enough power for LED lights, a low-power amplifier, and a smartphone. For a laptop, this homemade dynamo is not enough.
So, review. The wall and bottom are made of laminate, the remainder is left over after the renovation. The belt pulley is made from optical discs, which are unnecessary as you can see they have been drilled and twisted. The belt is large, long, yellow, from an old printer, just like the tensioner from the old printer, it was larger. I sawed off the unnecessary part.
The generator remained the same, the handle was also curved, this is necessary so that it does not cling to the belt and tensioner. It was curved, and the position of this handle changed, it was more convenient. In this case, the optimal gear ratio is achieved. Also new is a stiffening rib, because the laminate walls turned out to be too high, and it began to sway a lot, thanks to it everything is secure and nothing wobbles.
It is worth saying the following. The generator, diode and capacitors remained exactly the same as in the previous dynamo. One toggle switch and a battery pack were also added. I added connectors accordingly so that a load could be connected to it, conveniently through the connectors. On the left is a piece of a sawn-off laptop motherboard, a faulty motherboard. We got 3 USB ports for connecting power. A little to the right is a homemade scarf, a breadboard with 5 pins. Accordingly, 5 energy consumers can be connected and 3 energy consumers can be connected to 3 USB ports.
As a result, in total, in parallel, 8 consumers can be powered simultaneously from this dynamo, but for now only 2 consumers are in operation, I’ll tell you about them soon. The toggle switch is located at the front, and this is what the dynamo looks like from below. Nothing special to look at: 4 rubber feet are glued to double-sided tape and 2 screws from the stiffener.
Note. The screws with which the disks are twisted are with a countersunk head; There are transverse notches on the pulley (otherwise the belt would slip) and the “piece of iron” on which the pulley rotates is a core from an old speaker. The batteries are attached to metal plates with neodymium magnets, which, thanks to the nickel coating, conduct current perfectly. The metal plates themselves are from the transformer core. There is a thick lubricant between the pulley and the hardware, as well as between the pulley and the laminate.
An electrical energy generator is a device that converts chemical, mechanical or thermal energy into electrical current. Such a generator, used on bicycles to power the rear lights and headlight, is a dynamo.
Let's consider the existing types of factory-made bicycle dynamos.
This type of bicycle generator is the most affordable and simple. However, its power is not the greatest of all types. The generator drive roller rotates by touching the tire tread while driving.
The hub dynamo is an axial dynamo in its design. Executions of such models can be of various types. The cost of a bushing generator is quite high. Installation is more complicated compared to the bottle version.
When purchasing, you must check the number of spokes and the method of fixing the installation wheel. The advantages of a bushing generator include its protection from moisture, unlike a bottle generator, the drive roller of which slips over the bicycle tire in wet weather. The device is enclosed inside the wheel hub, and the work comes from its rotation.
The disadvantages of such a device include the fact that it is not possible to turn off the operation of the bushing generator.
The chain version of a bicycle generator is quite rare. However, there are several different versions of this type. The device can be equipped with a USB port for charging mobile gadgets.
The disadvantage of this design is its short service life, since during operation the metal bicycle chain impacts the plastic elements of the generator.
This is an original dynamo with a non-contact operating principle. The bicycle wheel plays the role of a rotor. A special hoop with 28 magnets is attached to the wheel. They are arranged alternately, with different poles.
The stator is an induction coil in which electric current is generated. This system includes a battery for energy storage. According to the manufacturer, to ensure normal light flux, it is enough to move at a speed of 15 km per hour.
The disadvantage of the contactless model is the low battery capacity. It only lasts a few minutes. However, many craftsmen easily correct this drawback in various ways, including replacing the battery with a more powerful one.
Currently, various interesting devices that are made in China are very popular. Sometimes you see devices that have never been produced anywhere before. Even their operating principle is not always clear, but they work.
This Chinese device can easily be called the bicycle generator of the future. The dynamo from heaven looks similar to science fiction films. Judging by its appearance, it does not require contact with the wheel bar or chain to function. There are also no magnets.
The principle of its operation is not entirely clear. Perhaps this is a technological secret of the manufacturer.
The most popular dynamo design on bicycles is the bottle design, followed by the hub dynamo. Other types are used much less frequently. Therefore, we will consider the most common models.
The bottle-type dynamo runs on the side of the front tire of a bicycle. It is made in the form of a small generator of electrical energy, and is used to operate the rear light and front headlight of a bicycle, as well as charge electronic mobile devices.
Such a mini-generator can be mounted on both the front and rear wheels. In the first case, the device can be combined with a built-in flashlight. To turn off the generator, a special folding mechanism is provided, which fixes the generator housing in a position where there is no contact with the bicycle wheel tire.
The name of this device comes from the external resemblance of the shape to a bottle. The bottle generator also has another name – side dynamo. The drive rubber or metal roller is driven into rotation on the side of the wheel tire. When the bicycle moves, the tire imparts rotational motion to the bicycle generator roller, which generates an electric current.
The hub design of the bicycle generator was developed in England and produced by various companies in many countries. The power of this design can reach 3 watts at a voltage of 6 volts. Their manufacturing technologies are constantly being improved, the dimensions of the structure are becoming smaller and more powerful. Modern bicycle headlights begin to emit more efficient light, as they are used.
Hub dynamos do not create noise during operation, but their mass is greater than that of other models. There are no rubbing parts in the sleeve version of the device. They operate due to a magnet having many poles and made in the form of a ring. It is located in the bushing body and rotates around a stationary armature with a coil fixed on the axis. The rotational resistance of this design is very low.
Hub dynamos produce alternating current. At low speeds, more electricity is generated compared to the bottle model due to the low frequency of the current. There are rectifier circuits for a dynamo. They are made using a simple bridge circuit of four diodes.
The hub dynamo produces a low voltage, so when using silicon diodes the losses are significant - 1.4 volts. With germanium diodes, losses are reduced and amount to only 0.4 volts.
A dynamo produces electric current using the effect of electromagnetic induction. The rotor rotates in a magnetic field, resulting in an electric current in the winding. The ends of the rotor winding are connected to a collector made in the form of rings. Through them, with the help of pressing brushes, electric current enters the network.
The current in the winding has a maximum value if the rotor is perpendicular to the magnetic lines. The greater the angle of rotation of the winding, the less current. Rotation of the winding in a magnetic field changes the direction of the current twice in one revolution. Therefore, the current is called alternating.
A similar generator for direct current is made on the same principle. The difference is in some details. The ends of the winding are connected not to rings, but to half rings, which are isolated from each other. When the winding rotates, the brush contacts each half ring in turn. Therefore, the current flowing to the brushes will have only one direction and will be constant.
A bicycle generator is a device that allows you to generate electricity by rotating the pedals and transfer it to the bicycle’s lighting fixtures or third-party electrical appliances. By design, bicycle generators are divided into several types: bushing, bottle, carriage and contactless.
The current and voltage output are inextricably linked to the pedaling frequency - the speed of movement. The pattern is valid for all types of generators. The bicycle generator produces alternating current, which is stabilized into direct current using a bridge rectifier. Its role can be played by soldered diode lamps or special devices, for example, a full-wave rectifier.
A hub dynamo, or bushing generator, is a regular one with a built-in magnetic mechanism. During rotation, eddy currents are formed; at the exit from the bushing, mechanical energy is converted into a current with a given force, voltage and power. On bicycle dynamos, the voltage reaches 6V and the power is 1.8-2 W.
The invention was patented by the English company Sturmey Archer. Nowadays, production is actively supported by other manufacturing companies - Shimano and Schmidt.
Features of the generator bushing design:
Dynamic Shimano AlfineDH-S701
The bushing source of electricity does not use the bicycle frame as a ground and, together with the lamps, is isolated from it. In a full-wave rectifier, the AC circuit (output) and DC circuit (to the headlight) are completely separated from each other.
Hub dynamos are heavy, although lighter rare-earth magnets and an aluminum shell have made it possible to slightly reduce their weight. In operation, the device has low resistance to unwinding, and as the angular velocity increases, the frequency of the current increases. This effect smoothes out the voltage gain and allows the generator to operate over wide speed ranges.
The headlights that the bushing generator is equipped with have a built-in current stabilizer. When connecting another headlight, a separate rectifier is installed in the circuit so as not to burn the electrical appliance. The brightness of the headlight depends on its requirements for the energy source and, in fact, the output voltage of the bushing. The greater the discrepancy downward (the headlight is more powerful), the dimmer the light will be. In the opposite situation, the light source will not work.
Let's get acquainted with another energy source - a bottle, or “bus” converter.
A bottle electric generator is a closed housing with a rotating rubber roller on the outside, attached to the front fork. The housing contains the direct converting device – winding and magnets. The movement of the magnetic field is achieved by engaging the roller with the tire and directly transferring mechanical energy from the wheel to it. The higher the speed, the stronger the polarity inside the generator and the greater the voltage output.
"Bottle" is afraid of bicycle falls
Advantages of "bottles":
Weaknesses include:
Separately, it is worth mentioning the carriage bicycle generator. Its body is fixed in the area of the pedal assembly - the carriage, under the lower stays. The rotation of the magnetic device is set by a roller that is engaged with the rear wheel of the bike. The roller is secured to the tire by a clamping spring.
The bottle and carriage generators produce electricity when they come into contact with the moving wheel. The hub dynamo is a built-in element of the wheel. The contactless generator does not touch the wheel in any way and does not create friction forces or resistance to rotation. Eddy currents are formed due to the close proximity of the plane of rotation of the magnetized rim and a strong magnet.
The headlights are built directly into the device, electricity is transmitted directly through the rectifier bridge. The undeniable advantages of this generator include:
Non-contact energy sources can be safely used on road bikes for long journeys
The devices are attached in pairs: on the fork - the headlight, on the feather - the rear reflector. In fact, these are independent flashlights, only they do not work from batteries, but through the rotation of wheels in a magnetic field. The luminosity of the lamps is at the same level as or exceeds that of battery-powered lighting devices.
As the wheel slows down, the intensity of the eddy currents decreases, the lights should dim, and when the wheel stops, they should go out completely. To ensure uniform light and the ability to use the light even when parked, the design includes a capacitor (“battery” for generating electricity), which is filled when the bike moves.
Now let’s try to make a generator for a bicycle ourselves. We will use a stepper motor as a basis. To power the lighting devices you will need a motor with the following characteristics:
The dynamo should be installed near the rear wheel hub. To transfer rotation from the wheel to the flywheel (rubberized wheel) of the motor, a transfer ring is needed. To create it you will need flexible plastic tape. Manufacturing:
When the ring is ready, a stepper motor is screwed onto the free seats on the feathers, and the flywheel is installed on top of the ring. If there is no free space for the engine, you will need to weld an additional plate with holes onto the frame.
General diagram of creating a generator with your own hands: generator - assembly of the electrical circuit (bridges, resistors, capacitors) - connection - installation of headlights.
To assemble the electrical unit for the headlights you will need:
We assemble the components taking into account the following diagram:
Another version of this scheme:
Assembly sequence:
Homemade electric generator for the rear wheel of a bicycle
The housing with the electrical circuit is fixed on the bicycle frame, the wires are secured with clamps.
At the last stage, the operation of the system is checked: the wheel must move freely along the wheel and move synchronously with it. With a correctly assembled electrical circuit of capacitors, resistors and rectifier bridges, the headlight will turn on. True, at low wheel speeds its light will flicker.
An electric generator will allow you to extract additional benefits from pedaling - receiving absolutely “free” energy to illuminate your two-wheeled vehicle when driving along a dark highway or rough terrain. Small and useful, this device requires virtually no maintenance and can easily be assembled yourself.
Those who still remember their school days probably haven’t forgotten the feeling of being involved in a small miracle in a physics lesson, where the teacher clearly demonstrated the transformation of muscle muscle into electricity. Modest in size and capabilities, the dynamo, without any wires, sockets or batteries, turned the handle on and lit a light bulb - and the faster the handle was rotated, the brighter it burned.
The feeling of miracle, however, was mixed with healthy skepticism: the age of electricity, sockets at almost every step, batteries in stacks. So is it worth working with your hands and feet if they are the fruits of great discoveries?
But what will you do if you get lost in three pines and discover that the charge of your newfangled gadget or even an old mobile phone is running low?
By the way, those who drove recklessly on two-wheeled vehicles in childhood are very familiar with the idea, which is already more than a century and a half old. The simplest dynamo for a bicycle, assembled literally on the knee and mounted on the front wheel, fed a flashlight bulb from the free energy of pedaling, which illuminated the road as it glowed.
The merits of Faraday's discovery were also appreciated by the military. In fact, a battery only has value as long as it has charge. Having spent it, it turns into a useless heavy object, instead of which it is better to take another zinc with cartridges. Need energy? What about the soldier? Let him turn the generator handle properly to ensure the radio works. (That’s why that generator was popularly nicknamed “soldier-motor.”)
In principle, little has changed with the advent of the era of high technology. Gadgets are gadgets, and without power supply their value is zero, especially if there is nothing to charge them in the near future. The value also disappears in cloudy weather or at night. The dynamo is more than unpretentious in this regard. If only there were a person who could turn a handle, there would be current!
The pioneers in this matter, of course, were craftsmen who were accustomed to the fact that almost everything in this world, including a dynamo, must be made with their own hands. Self-taught people did not skimp on sharing their achievements, and as a result, specialized magazines were filled with photographs and drawings of simple devices that easily recharged the batteries of flashlights, mobile phones, smartphones and GPS navigators. Fans of cycling haven't forgotten either: a long ride is enough and the “on-board” dynamo will provide a full charge for your iPhone or iPad.
Finally, having seen the benefits of the practical use of visual aids from their school years, professional producers followed the amateurs. Now there are enough portable devices on the market that convert the user's muscular energy into electric current for almost any electronics. For example, a small LED flashlight that fits in the palm of your hand has a folding handle. It is enough to rotate it for a minute at a speed of two revolutions per second for the device to shine for several minutes.
It is also very pleasing that in parallel with this equipment, a dynamo is also being sold, specially designed for teenagers interested in science. By endlessly experimenting at home, you can not only figure out how to get environmentally friendly electricity without batteries, but also invent something new...
