Bicycle Dynamo

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FAQ about Bicycle Dynamo

What is the average voltage generated of a bicycle dynamo? If I combine two dynamos together, does the voltage generated would be double? I've never played with these. First, determine if they are DC. Some multimeters will not respond to AC if it is a DC voltage. (On the other hand, some do). You could check the manufacturer's specs or if available, an oscilliscope.
If it is DC, you can connect them in series to get a higher voltage. If they are AC, you cannot because frequency and phase differences will cause unusual effects.

Can I replace the tungsten bulbs in my old bicycle dynamo with modern LEDs? Though I much prefer it to using battery powered lighting, I'm getting tired of the frequency of which I'm having to replace the rear lamp on my bicycle dynamo. LEDs are of course much brighter and last far, far longer, and I've discovered a website that sells them for pretty much the same price as the old tungsten bulbs. Will these work with the unstable voltage that a dynamo provides? Yes, but you'll need to add an electrolytic capacitor to the mix- between the bulb and the dynamo. The capacitor value should be pretty easy to work out. Most anyome that works in an electronics repair shop could tell you exactly what you need if you can provide the maximum output of the dynamo.
Here's how it would work: the dynamo places a charge into the capacitor and the capacitor lights the LED. Easy.

Is it possible to generate electricity from bicycle dynamo and charge a 6v battery? A bike dynamo consists of a rotating magnet and a fixed coil, with a rating of 6V and 3W. They are current limited by design to some extent (see third link), so just connecting to a battery with the dynamo going fast enough will charge the battery at 0.5A (which should not be exceeded as it is the rated current.
So the answer is yes, if the RPM is in the correct range. The output is AC so it needs to be rectified by a bridge rectifier. As they are not properly regulated, there needs to be some form of charge control, either by speed control, or a controller in series with the charge connection. A basic controller would probably switch the charge on and off to protect the battery from overcharge. The current produced is in the range of 0.5A (6V at 3W) so would take 20 hours or more to charge a 7 Ah battery. It is more suitable for a 4 x AA cell sized nicad or NiMH battery.
The link below shows a charger circuit that probably suits. It just switches the charge off at a particular voltage. Note the use of Schottky diodes for the rectifier to minimise voltage loss.
In the second link the battery is connected to the points named V+ and V- in the circuit.
The last link determines the characteristics of a dynamo with a simple model. It is apparent you can regulate the voltage a little by connecting back to back 7.5V zener diodes across it.

What type of current is made from a bicycle dynamo and explain how this current is made.? What happens is the soft iron core of the dynamo as the magnet rotates? I know AC is generated but I'm having trouble explaining how. When a conductor e.g. an electric wire moves through a magnetic field a electric current is induced in that conductor! This principle is used in the make-up of a dynamo in the form of a rotor (movement/motion) magnets (magnetic field) and lots of electric wire wound in loops (conductor).

do anyone know what project can I invent using only a simple bicycle dynamo? something that can be used globally. practical and easy to be used. something that is only built using the reused substances. plz help me... If you are referring to the old military hand-cranked generators, they could be used for many purposes. I think they put out a good bit of power for the old vacuum tube radios.
If you mean small ones for headlamp power, like was on my English Lion bicycle I had when I was a kid, those would be more limited. Any small semiconductor device, like the ones suggested, could be applied. The device would be the invention.
You might be able to electrolyze water producing small amounts of hydrogen and oxygen. Those were used for rocket engines and burning them together produces great force. You could run a small turbine at high speeds. Heat dissipation and robust materials must be carefully considered.
Be careful, though, hydrogen is explosive, particularly in a concentrated oxygen environment. The hydrogen should never be mixed with air or oxygen except within a combustion facility capable of accepting the resultant heat and pressure. If you aren't careful enough, you and people around could lose parts, or all, of their bodies.
None of it's very practical. Useful amounts of power still requires natural water pressure, fossil fuel combustion, or nuclear reactions for efficient production. The power realized needs to be significantly greater than what is inducted to produce it. Otherwise, the effort is wasteful or completely pointless.

looking for bicycle dynamo to charge 12v batteries? I need a bicycle dynamo capable of charging a 12v basic motorcycle battery i will carry with me on long trips. It need to be one that is simple to remove resistance when charging is no longer needed or when making climbs etc... Dream on. If you are riding along on a bike you simply don't have enough extra energy to recharge a 12 v motorcycle battery. Even top professional racers would be hard pressed to do this. I don't know what you need this battery for, but you need to do some basic research about electrical power and batteries. Bicycle dynamos can run a small light and not much more. The only ones that are moderately efficient are hub dynamos, and they run all the time

How do you build a simple bicycle dynamo? I was just wondering how to make a simple, easy to build dynamo to attach to my indoor bicycle machine, for a school project. The main goal is to connect the dynamo to the bike, and a small lamp that will light up as one pedals on the bicycle machine. Thanks Here's one set on instructions, but it looks rather complicated. I'll keep looking:
http://www.freelights.co.uk/howmake.html
Here's what you're looking for, I believe:
http://www.practicalphysics.org/go/Experiment_345.html;jsessionid=alZLdQlAHb1

How would one install a bicycle hub dynamo, with out buying a new set of spokes, and/or rim? Will the spokes we have curently fit the dynamo? If this is not so, where can we get the right sized spokes? We are highschool seniors and we have a budget of around 50 dollars, also only about 50 days left to finish our project. Any info or advise is greatly appreciated. Thanks! oh good grief
you are hosed
no they won;t fit if the dyno hub is differently sized than the original - which it probably is
also the dyno needs to have same number of spoke holes as the rim
1 thing only i will tell you - go to a bike shop - we can;t see what you are talking about
wle

What is the minimum rpm to develop 20 V from a normal bicycle dynamo ? Maximum emf rating on the dynamo is 20 V and normal bicycle dynamo in the sense the dynamo used for bicycle purposes. If you are anxious that the dynamo should not burn out, do not worry. At the maximum speed at which you can travel in bike (40kmph??), the voltage will be still not 10 times 20V etc. You need to load the dynamo generated voltage with a bulb. As voltage gets fed to this bulb, in a way, the bulb will act as a limiter for normal speeds of travel in bicycle. You can (- this will be simple-) estimate the rpm, as k*rpm of wheel, where k = ratio of wheel dia to the dia of the part that in dynamo that makes physical contact with the wheel rim.
Let me try an experiment....

How would I fix my bicycle's dynamo? I have a vintage dynamo for my bicycle that doesn't generate any power. Both lights work when connected to another power source, so it is the actual dynamo that won't generate power. What could be causing this, and how would I fix it? And please don't bother answering if you're just advising me to get a new one. I could get a new one, but I want to repair this one as it is surely a collectable by now. It's proberly the wire coil that's gone put a Volt/Amp meter on the + to - terminals (output to the dynamo body) and check the Ohms resistance if its 0 then the wire coil has a break tricky to fix, if thats giving a reading then the magnets surrounding the coil have lost there strength or corroded connections.

Bicycle Dynamo is from category: Flashlights.