| Author | Message | ||
     ABCinventor Unregistered guest |
Hi Simon, its been a long time since i came to scitoys. i have been planning to build an electric generator by using a DC motor. the problem is how do i find a dc motor that is sensitive enough to generate power even if it is ran at low RPM. Also, i have trouble choosing different sizes of motors from high speed to solar motors and high torque. Some are large(little larger than a D size D-cell) to small ones(about the size of N size D-cell).From 3V to 12V. Please help me in this project especially on the sensitivity part. Thanks Simon | ||
| Alessandro Carcione (alessandro) New member Username: alessandro Post Number: 15 Registered: 2-2005 |
Dc motors just can't generate enought current at low speeeds you will need to build an alternator, check out http://www.otherpower.com/otherpower_experiments.html The powered alternator or the wood 103 you be best stuited to you, also there is a guide for choosing the correct alernator. Also, although they do tell you how to use a DC motor for a generator I would advise it. Also an other thing, you could open up the motor and rewire it so that it does need to go as fast to generate current, but from personal experience it isn't worth it, you bet bet is to make an alernator from NIB magents | ||
| Anonymous |
Or you could just use gears to increase the speed. | ||
| Alessandro Carcione (alessandro) New member Username: alessandro Post Number: 16 Registered: 2-2005 |
That would mean friction losses, the last thing you want and dc motors are horribly inificant as generators | ||
| Alessandro Carcione (alessandro) New member Username: alessandro Post Number: 17 Registered: 2-2005 |
That would mean friction losses, the last thing you want and dc motors are horribly inificant as generators | ||
| ABCinventor Unregistered guest |
i just bought the DC motor yesterday and they can produce well over 25V with just a light spin by hand. i am going to mount it on some gearing systems as it is difficult to mount it on my bike. the motor is a high torque while low RPM motor and it is very hard to stop when supplied with a 12 V power supply. Now i am trying to make it a hand cranked system as the bike mounting is too unstable and fell out just now. well now i am having trouble searching for correct gear box and so on.please tell me how i can find those items. Thanks! | ||
| ABCinventor Unregistered guest |
Another thing, how do i become a member??... | ||
| ABCinventor Unregistered guest |
Hey how about using a belting system? will it be efficient?? a little wastage of energy may be fine and also it is inevitable...  | ||
| Alessandro Carcione (alessandro) New member Username: alessandro Post Number: 18 Registered: 2-2005 |
Any type of conversion system losses engery as friction I would either go for a belt or gear system. By the way how many amps is your motor outputting? | ||
| ABCinventor Unregistered guest |
eh not sure , i haven't measure as i didn't have the instruments. i will go to my school to measure when school reopens. By the way, i had made a fine generator by doing several modifications to a video casette rewinder. with some glueing and some additional acrylic pices, it is quite secure and stable. the gear ratio is 1:8. 1 being the hand crank and 8 being the output. | ||
| Alessandro Carcione (alessandro) New member Username: alessandro Post Number: 21 Registered: 2-2005 |
Get a cheap $8 dollar muiltimeter so you can meausure votlage, current and resistance, It doesn't cost much and it is worth it. | ||
| Alessandro Carcione (alessandro) New member Username: alessandro Post Number: 22 Registered: 2-2005 |
To become member just e-mail simon with your desired username and password. | ||
| Simon Quellen Field (sfield) Senior Member Username: sfield Post Number: 279 Registered: 12-2004 |
To make a generator for lower speeds, just use a DC motor that is designed for higher voltages (such as 12 volts or 24 volts). These have more windings. | ||
| Janika Unregistered guest |
How do I make an electric generator, nerdy-mc'nerds? | ||
| Simon Quellen Field (sfield) Senior Member Username: sfield Post Number: 320 Registered: 12-2004 |
Well, you could read the messages above this one. Or you could move a magnet past a coil of wire. | ||
| GlobalFusion Unregistered guest |
Say I have 14 Coils, each with only 10 windings @ approx 20mm in diameter, evenly spaced and connected in series. (I had a small bit of copper wire left, thought id try something) How would i best reach minimal effeciency? Below is a diagram to help explain:  | ||
| Simon Quellen Field (sfield) Senior Member Username: sfield Post Number: 346 Registered: 12-2004 |
To get minimal efficiency, short each coil. To maximize output, use more windings on each coil, and spin the magnet as fast as you can, and get it as close as you can to the coils. Adding a ferrite (or even steel) core to the coils will probably also help a good deal. | ||
| John P Becich (johnpeter) Junior Member Username: johnpeter Post Number: 6 Registered: 4-2005 |
May I attempt to explain the basic differences between alternators (so commonly found in modern automobiles) and generators (commonly found in automobiles, before, say, 1960)? Alternators have "electromagnets," in their rotating cores ("armatures"). Generators use permanent magnets in their rotating cores. Alternators have solid state DIODES, which weren't even invented until the 1950s...so there was no such thing as an alternator before that. Why would alternators be more EFFICIENT than generators? I suspect that alternators are easy to regulate, because that electromagnet in the rotating core (also called the "field winding") can be manipulated by the car's overall voltage. The permanent magnets in a generator are fixed, in their magnetic strength. Though there are field windings in the armature of a generator, the strength of the magnetic field there is not adjustable externally. Generators, therefore, will generate their greatest power when they are spinning fastest. This is not what an automobile needs. A car needs to recharge its battery immediately after the engine has been started, and that generally occurs at low speeds. Conversely, the excess power generated by a generator, while a car drives long distances at high speeds, must simply be wasted into heat. Here an alternator shows its value, by pumping lots of power when it is needed. A voltage regulator will tell the alternator to do that. Then, when cruising on the freeway, with a fully charged battery, the field windings of the alternator will be relaxed, and the load on the engine will be thereby lessened. Unneeded charge will simply not be created in the first place. Generators, which are really DC motors used "backwards", use copper COMMUTATORS and carbon BRUSHES, just like motors do. That is, as a generator core rotates, its electrical output current continues to flow in one direction, thanks to its commutator. Furthermore, the bulk of the current that a generator creates must flow though the brushes, a notable bottleneck. Brushes wear out, too. Now let's get back to those DIODES, which rectify alternating current (turn alternating current into direct current). Alternators don't commutate. They have slip rings and brushes, and a relatively small current flows through them...only the field winding current. The big current produced by an alternator is produced in the outer part of the alternator, which is physically fixed and doesn't rotate. This allows for bigger wiring and no brush contacts for massive electrical currents to travel through. This "stator" winding, therefore, is rigidly hard-wired into the car's wiring. The catch is that the current generated this was is alternating current, which is useless to the direct current system that cars use. Useless, that is, until it is rectified...by those diodes that are pressed into the backside of the alternator. The massive automobile battery helps "filter" the bumps in the resulting rectified current, so that the voltage is smooth. Batteries are like gigantic capacitors. Can anyone add, or correct, my suggestions here? | ||
| MadScientist (madscientist) Intermediate Member Username: madscientist Post Number: 41 Registered: 4-2005 |
Theres one part about magnetism that has always confused me somewhat, and that is (as mentioned above by Simon), the addition of a ferrous or steel core to a coil increases its output. Its pretty obvious that this is actually the case, the confusing part is how? Since the current is produced by the magnetic field cutting the turns of the coil, how is it possible that an increase in output actually takes place considering that the lines of force will concentrate *inside* the core, effectively diverting them away from the coil(?)... This process is easily visualized by taking a strong magnet, placing it on a piece of steel so that the polarity of the poles are parallel to the steel (as in a magnet 'keeper' configuration), and then trying to get something magnetic to stick to the other side of the plate. There may be some magnetism there, but it is definitely much weaker than if the object were being brought the same distance from the magnets without the plate present. | ||
| Simon Quellen Field (sfield) Senior Member Username: sfield Post Number: 363 Registered: 12-2004 |
The permeability of iron is much higher than air. Thus the magnetic flux will flow in the iron instead of the air, by an amount equal to the ratio of the permeabilities. | ||
| MadScientist (madscientist) Intermediate Member Username: madscientist Post Number: 42 Registered: 4-2005 |
So if it flows through the iron, its not cutting the coil, which is for all practical purposes and intents, in the 'air'... if its not cutting the coil, how does the power output increase? | ||
| Simon Quellen Field (sfield) Senior Member Username: sfield Post Number: 367 Registered: 12-2004 |
You're forgetting what Michael Faraday taught us. What is important is not how much flux is near the coil. What matters is how much the flux changes. When you hold a magnet in your hand, the flux extends well past your hand -- that is why a nearby compass will point to your magnet. If you bring a piece of steel near the magnet, the flux will concentrate in the steel, and the compass will not see as much flux in its vicinity. The flux has moved, from the air into the steel. If there is a coil in the flux, moving the steel will cause the flux to move, generating a current. Now, if you have a coil with no steel inside, and you pass a magnet nearby, only some of the flux will pass through the coil, so the coil will not generate a lot of current. But if you have some steel in the coil, the flux from the passing magnet will have to move through the coil to concentrate in the steel. More current is generated, because more flux has moved past the coil. When you remove the magnet, the flux leaves the steel, passing through the coil again, and generating current again. | ||
| MadScientist (madscientist) Intermediate Member Username: madscientist Post Number: 43 Registered: 4-2005 |
Ahhh.. so now tell me this.. If you replaced the steel with another magnet aligned with the same polarity, could this increase it that much more by adding to the overall flux, or would it just waste input energy by trying to trap the passing magnet? | ||
| Simon Quellen Field (sfield) Senior Member Username: sfield Post Number: 371 Registered: 12-2004 |
The magnet would be closer to saturation than the steel. If it became saturated, it would not be able to hold any more flux, and would thus not participate in any further flux movement. No energy would be wasted. Think of the magnetic field as a dip in the road. You accelerate as you enter, and decelerate as you leave. | ||
| Russian Wolf Unregistered guest Posted From: 207.162.152.129 |
hey, i think it would b great 2 make an electric generator powered by a bike(imobile) but i dont no how. do u? | ||
| justine aquino (Mnado) New member Username: Mnado Post Number: 3 Registered: 12-2005 |
just strip a dc motor and see what it looks like,now if you know what does parts are for just make a copy or make the bike's wheel the armature,..of course with the magnets and coil thing? | ||
| Twors (Twors) Member Username: Twors Post Number: 13 Registered: 7-2006 |
well a mobile one u could just get a 3rd gear onto the chain and gear down until spinning hobby dc motor at the correct speed to light 2 super bright LEDs and u could bike at night would making such a system be cheaper than buying one for ur bike, or buying cheaper? | ||
| Twors (Twors) Member Username: Twors Post Number: 14 Registered: 7-2006 |
Hey I have a problem. Let's say two situations with a stator that looks just like GlobalFusions, except with steel inside each coil. 1) My two ceramic magnets' diameter are just a little smaller than the inner diameter of the stator. I have them on the axle one above one below, both outer faces of the magnets are the same polarity. I spin it by hand, and it is fast enough to light up 2 LEDs very brightly. 2) I found out at the rpm I will actually have it is slower than spinning by hand. So I go for rare earths. Now I have 7 magnets, 1 magnet "trying" to align with every 2 steel laminates, alternating. Of course I say "trying" because precision is none existent. Now I have no voltage whatsoever and current very very discouraging. What is the problem? Lack of precision lining up the magnets to the steel? The rare earths are so close to the steel that it is very tough to rotate so distance is not factor. Not only is the alignment completely off, but the axle is not even in the center of the stator. Plz help. Thank you. (Message edited by TwoRs on October 23, 2006) (Message edited by TwoRs on October 23, 2006) |
