Hand Crank Flashlight Home Page

How does it Work?
The History of the Dynamo

Hand crank flashlights are a convenient, ecologically friendly source of light. They are also incredible safety devices, with many offering not only dependable light, but also the opportunity to charge other devices such as cell phones, the ability to listen to AM/FM and even NOAA weather broadcasts, blaring sirens one can use to signal for help, or even transistor radio capabilities. This type of flashlight comes in handy in particularly aggravating or potentially dangerous situations, such as when your batteries are dead, because the inner-workings of a hand crank flashlight can take the energy a user puts into it via turning the crank in use it to power the light or other functions of the device. In our world today, it seems that everyone wants to be more environmentally friendly, find renewable energy sources, save money and simplify his or her lives. The hand crank flashlight seems to fit perfectly into our current desires during this modern time, but this technology is almost two hundred years old.

Hand crank flashlights, or dynamo—meaning generator—flashlights, are not a new invention. Michael Faraday discovered the concept upon which they operate during his research into electromagnetic induction in the 1820s. Faraday found that by wrapping two insulated coils of wire around an iron ring and applying an electric current to one of the coils a brief current passed through the second coil—mutual induction. Upon further experimentation, Faraday found that if he moved a magnet through a loop of wire an electric current passed through the wire as well and that the current passed if the loop travelled over an immobile magnet. His work revealed that a dynamic magnetic field creates an electric field, now taught as the “Field Theory”. This knowledge helped build the first dynamo—electric generator—in 1832.

Two vital parts must exist in order for a dynamo to operate successfully: A stationary structure to provide a constant magnetic field and a set of rotational windings able to rotate 360° inside of the field. On smaller dynamos, such as that found in hand crank flashlights, a permanent magnet provides the constant magnetic field and a handle or interlocking twisting apparatus or even shaking the item serves as the rotational winding. Without one of these two objects, in these circumstances, it is impossible to create the necessary electric field to generate the power required to power the light bulb of the flashlight.

Dynamo flashlights work using this method to create energy that powers the flashlight, making the light come on, and some dynamo flashlights have a rechargeable battery while others do not. The important difference between a dynamo flashlight and a battery-operated one is that the power is generated from the user’s manual cranking, shaking or twisting instead of drawing energy directly from an alkaline, lithium or other type of battery. In dynamo flashlights with a separate rechargeable battery, the manual cranking will create power to recharge the batteries without finding an outside electrical source such as a wall outlet. In crank flashlights without such additional batteries, the manually created energy is stored inside of internal rechargeable battery cells. The strength and duration of light in a hand crank flashlight varies. In many of today’s hand crank flashlights 30 seconds of cranking can give about five minutes of bright, reliable light.

In the present day we have available to us a seemingly endless supply and infinite choice of battery options; lithium, alkaline, disposable, rechargeable—why would anyone in today’s world need such a seemingly aged and outdated energy source? It is not as if today’s average person is in an environment similar to that of the battlefields of World War II, where such hand crank flashlights as the “knijpkat” were included in the AAC emergency sustenance kits of soldiers, or in the skies above those fields where models like the A-9 were tucked securely away in the flight suits of fighter pilots above Europe. Why are hand crank flashlights significant to today’s members of modern society?

Now that we have some history on dynamo technology, lets take a look at some reasons you would choose a handcrank flashlight.