# How do you reduce voltage and make a current last longer?

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Ok so I have another question: What if I have a situation where the rotor can rotate in either direction? I'll still get an AC current, but won't the polarization reverse every time the rotation goes from being clockwise to counterclockwise?

AC means Alternating Current and the polarity is constantly reversing. Why would you want to change the direction of the rotor? Whatever is driving the rotor you can use gears or pulleys so as to keep the rotor turning only one way.

How would I rectify that to make a single DC current through the whole thing? Would I need a diode on both sides of the circuit, both going into and coming out of the alternator, and, would both diodes have the same orientation?

This doesn't make much sense in light of what AC is as I just noted.

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But having a system of gears and pulleys is inefficient and out takes away a lot of energy from friction and costs more money and is a lot more complicated, surely there must be a way to use diodes to cerrect it. If I have wind, well, the wind can rotate in all sorts of directions at different angles at different times and make eddies and negative pressure and ect. If something's blowing every which-way in the wind but I want a constant current in one direction, how would I do that without a bunch of pulleys and gears? Do I only need one diode?

Oh wait a minute, so it requires work for electricity to pass through the magnetic field when the generator isn't rotating from an external source?

Edited by MWresearch
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But having a system of gears and pulleys is inefficient and out takes away a lot of energy from friction and costs more money and is a lot more complicated, surely there must be a way to use diodes to cerrect it. If I have wind, well, the wind can rotate in all sorts of directions at different angles at different times and make eddies and negative pressure and ect. If something's blowing every which-way in the wind but I want a constant current in one direction, how would I do that without a bunch of pulleys and gears? Do I only need one diode?

Wind mills rotate in only one direction because of the pitch of the blades. Using a vane, they also orient themselves to point always into the wind. They also need gears in order to spin the alternator at a high enough speed and the friction is and always has been just part of the bargain.

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Ok, but, what about all the other stuff I said about when the alternator randomly reverses direction? Clearly it matters or so many alternators wouldn't be designed to work in only one direction as you pointed out with the windmills.

Edited by MWresearch
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Actually there are wind mill design that rotate no matter the wind direction. Here is an illustration:

Ok, but, what about all the other stuff I said about when the alternator randomly reverses direction? Clearly it matters or so many alternators wouldn't be designed to work in only one direction as you pointed out with the windmills.

The alternator is not going to randomly reverse direction. This is ensured by the mechanical design of the driver.

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Since an alternator generates AC it doesn't matter much which way you rotate it.

And it isn't just modern windmills that always rotate in the same direction. Here's an image pinched from the web where you can see th esmall wheel at the back. Its job is to keep the main set of sails pointing into the wind.

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Since an alternator generates AC it doesn't matter much which way you rotate it.

And it isn't just modern windmills that always rotate in the same direction. Here's an image pinched from the web where you can see th esmall wheel at the back. Its job is to keep the main set of sails pointing into the wind.

While the alternator will produce electricity in either direction, the nut holding the pulley on can be unscrewed when running the alternator 'backwards'. If for some reason it is necessary to run backwards the nut needs to be secured with some locktite®, peening, or other method.

Nice pic. That back wheel is a rather more complex version of what I meant by 'vane'. Perhaps it is so built in order to have enough power to turn the large structure. What I had in mind was the old wind mills used to pump water in America back in the day. (Well, they are still used though they have been around more than a century.)

Illustrations of American wind pumps here, as well as an exploded diagram of the whole mechanism including the gearbox.

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Ok so I have another question:

I will give you +1 for seeking for knowledge..

What if I have a situation where the rotor can rotate in either direction?

I'll still get an AC current, but won't the polarization reverse every time the rotation goes from being clockwise to counterclockwise?

All this is easy to see if you have oscilloscope and toy electric motor. Do you have?

Connect electric motor directly to oscilloscope (because it shows past values on graph), or multimeter (it'll be harder).

And start spinning it manually. You should see voltage is f.e. +some value on graph or display of multimeter.

Then start spinning it opposite. You should see voltage is -some value.

How large is this value depends on how fast you're spinning it by hand.

How would I rectify that to make a single DC current through the whole thing?

source of energy is in this case spinning rotor of electric motor,

so treat is as any other source of power.

Attach it to rectifying bridge, and on output from bridge there will be pulsing DC.

Would I need a diode on both sides of the circuit, both going into and coming out of the alternator, and, would both diodes have the same orientation?

You would need four diodes, or one rectifying bridge.

And then, if I have one wire running through the whole alternator, is there any sort of phase differential caused by different parts of the wire being exposed to different parts of the magnetic field? Or, do phase differentials only occur when all the wires are separate for each magnet in the stator?

I am confused by your questions here.

In showed by me design of electric motor, magnets are is stationary stator, and wires are around iron cores (electromagnet) in rotating rotor.

It's not just one design of electric motor.

It can be swapped (magnets in rotor, electromagnets in stator).

It can have different quantity of magnets/electromagnets.

It can be plain wire, without iron core.

And that smoothing capacitor...If I'm not mistaken, a charge regulator converts a lower DC current to a higher DC current by absorbing a bit of current at a time and then re-releasing it in the form of higher-voltage pulses.

So the smoothing capacitor takes those pulses and then turns them into a regular DC current? Why wouldn't charge regulators automatically be built with that?

Why are you starting talking about charge regulators? When we're talking about electric motors. Not sure.

Charge regulator

https://en.wikipedia.org/wiki/Charge_controller

"Simple charge controllers stop charging a battery when they exceed a set high voltage level, and re-enable charging when battery voltage drops back below that level."

Also if the pulses are occurring at like 1000000 times a second, why would it matter if I have a continuous current vs a pulsating current?

Such large quantity of pulses per second are almost only in electronic oscillators

https://en.wikipedia.org/wiki/Electronic_oscillator

Smoothing is needed to not constantly switch on/off whatever is using our generator.

f.e. typical lightbulb is pulsing 100 per second, as it runs entirely on AC 50 Hz (50 Hz AC = 100 Hz pulses).

This can be seen after recording at high rate camera (even 120 FPS recording is sufficient).

Devices requiring steady DC current (electronics) wouldn't like it.

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All this is easy to see if you have oscilloscope and toy electric motor. Do you have?
Connect electric motor directly to oscilloscope (because it shows past values on graph), or multimeter (it'll be harder).
And start spinning it manually. You should see voltage is f.e. +some value on graph or display of multimeter.
Then start spinning it opposite. You should see voltage is -some value.
How large is this value depends on how fast you're spinning it by hand.

But that's the problem. In an AC current, it's not + the whole time and - the whole time for any given orientation of rotation. If I spin it ONLY clockwise, it will generate both + and - and create a sinusoidal pattern of electrical waves which switch from drawing charges from one direction to drawing charges from the other direction 100 times a second.

THEN, if I switch the rotation to COUNTERclockwise, the same type of pattern would occur except the voltage should be + when the clockwise wave would be - and be - when the clockwise wave would be +, so I'd have a double alternating current basically if it continuously switched from clockwise to counterclockwise, and it's not just windmills that try to avoid this, it's cars and iphones and all sorts of stuff. Basically, it would switch from +sin(x) to -sin(x).

source of energy is in this case spinning rotor of electric motor,
so treat is as any other source of power.
Attach it to rectifying bridge, and on output from bridge there will be pulsing DC.
s sufficient).

Wait, I need 4 diodes just to rectify one orientation of rotation? How many would I need to correct two? 24 diodes? Why wouldn't I need one bridge to rectify all input regardless of rotation? And furthermore, a rectifying bridge makes the output DC current pulsate?

Edited by MWresearch
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...

THEN, if I switch the rotation to COUNTERclockwise, the same type of pattern would occur except the voltage should be + when the clockwise wave would be - and be - when the clockwise wave would be +, so I'd have a double alternating current basically if it continuously switched from clockwise to counterclockwise, and it's not just windmills that try to avoid this, it's cars and iphones and all sorts of stuff....

Again, there is no actual situation using an alternator or generator where the direction of rotation changes. Not in wind mills, not in dams, not in autos. You are creating a problem where none actually exists.

...

Wait, I need 4 diodes just to rectify one orientation of rotation? How many would I need to correct two? 24 diodes? Why wouldn't I need one bridge to rectify all input regardless of rotation? And furthermore, a rectifying bridge makes the output DC current pulsate?

One bridge is all that is needed, regardless of the direction of rotation. Other than for sensitive electronic circuits -such as computers- it doesn't matter if the DC is pulsed.
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Do you know OpenOffice?

I attached project for calculator/excel.

You can load and see difference between AC, DC pulses (output from rectifying bridge, or four diodes), DC rectified by 1 diode.

If I spin it ONLY clockwise, it will generate both + and - and create a sinusoidal pattern of electrical waves which switch from drawing charges from one direction to drawing charges from the other direction 100 times a second.

Did you checked it in the real world experiment?

Normally electric motors create DC while spinning one direction. Especially toy electric motors.

Wait, I need 4 diodes just to rectify one orientation of rotation?

You need 1 diode to do max(sin(t),0) (cut negative part of wave)
and you need 4 diodes to do abs(sin(t)).
That's how I draw graph in OpenOffice project.

How many would I need to correct two? 24 diodes?

For normal single phase AC, 1 or 4 diodes are needed, no more, no less.

Why wouldn't I need one bridge to rectify all input regardless of rotation? And furthermore, a rectifying bridge makes the output DC current pulsate?

No. If source of movement is changing direction of spinning motor, it'll be pulsating AC.
If source of movement (whatever it is) just one direction, it'll be pulsing DC. And amount of pulse will depend on speed of spinning.

AC DC DC pulses.zip

Edited by Sensei
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Did you checked it in the real world experiment?

Normally electric motors create DC while spinning one direction. Especially toy electric motors.

I'm not at all talking about motors, just alternators and occasionally generators.

No. If source of movement is changing direction of spinning motor, it'll be pulsating AC.

That sentence is too choppy for me to interpret anything useful from it. So, do you mean, after putting in a rectifying bridge, the output current will be an alternating, pulsating current? Or, do you mean, prior to a bridge rectifier, the change of rotation from clockwise to counterclockwise will generate an AC current in the form of pulses that have both a crest and trough? Or pulses that have two troughs at a time and two crests at a time?

Do you know OpenOffice?

I attached project for calculator/excel.

You can load and see difference between AC, DC pulses (output from rectifying bridge, or four diodes), DC rectified by 1 diode.

Ok now all of a sudden you're not making any sense to me. I'm not trying to rectify a DC current, a DC current is already good to go, I'm trying to rectify an AC current from an alternator that can rotate both clockwise and counterclockwise and turn it into a continuous DC current.

Edited by MWresearch
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Ok now all of a sudden you're not making any sense to me. I'm not trying to rectify an DC current, a DC current is already good to go, I'm trying to rectify an AC current from an alternator that can rotate both clockwise and counterclockwise and turn it into a continuous DC current.

See screen-shot,

blue curve is initial input:

blue = sin(time)

So it's like AC.

red curve is:

red = abs( blue )

So it's like AC rectified to DC by 4 diodes/rectifying bridge.

yellow curve is:

yellow = max( blue, 0 )

So it's like AC rectified to DC by 1 diode.

Source of AC, is pretty meaningless.

Whether it's mains, or alternator, or electric motor spinning once in one direction, then other, theory works the same.

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See screen-shot,

blue curve is initial input:

blue = sin(time)

So it's like AC.

red curve is:

red = abs( blue )

So it's like AC rectified to DC by 4 diodes/rectifying bridge.

yellow curve is:

yellow = max( blue, 0 )

So it's like AC rectified to DC by 1 diode.

Source of AC, is pretty meaningless.

Whether it's mains, or alternator, or electric motor spinning once in one direction, then other, theory works the same.

Ok, so are you trying to say that, no mater what direction the alternator rotates in a single circuit throughout one period of time, like it rotates clockwise for one second then all of a sudden it starts rotating counterclockwise for half a second then starts rotating clockwise again, one rectifying bridge will make all output almost continuous in the form of closely spaced DC pulses?

What if there is sensitive circuitry? Is that what those smoothing capacitors are for?

Edited by MWresearch
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Ok, so are you trying to say that, no mater what direction the alternator rotates in a single circuit throughout one period of time, like it rotates clockwise for one second then all of a sudden it starts rotating counterclockwise for half a second then starts rotating clockwise again, one rectifying bridge will make all output almost continuous in the form of closely spaced DC pulses?

Yes. But again where in actual practice would the alternator change direction do you think? Because, again, I know of no application in practice where that happens. And again, there is no application where you can't avoid it mechanically. Please answer this so I don't keep asking.
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What if there is sensitive circuitry?

I am not too much experienced with alternators, but in normal electric motors, the faster spinning, the higher voltage.

So if it's exactly the same with alternators, which is what I suppose so.

Spinning too fast (if there is nothing like regulator), could cause damage of electronics connected directly to it, in certain extreme situations.

(Google shows plentiful of pages after searching for "alternator producing too much voltage", so it's real issue).

In such situations, voltage threshold triggered branch with zener diodes could be used, f.e.

Place fuse in horizontal branch instead of resistor.

Zener diodes f.e. 15 V.

If voltage is exceeding 15 V, current will flow through zener branch, instead of normal branch, and fuse will blow up, disconnecting entire circuit.

Such (or other) security elements should be used in circuits, regardless whether current/voltage regulators are present.

They might fail, and you need to be prepared for it in advance.

Single zener diode costs here $0.05. ##### Link to comment ##### Share on other sites • 2 weeks later... Gosh, I'm probably missing something obvious here but, capacitance is defined as Charge over Voltage, and of-course we can say that V=IR. So if C equals Q over IR, it seems like the easiest thing to do is to increase the resistance. Lengthen the wire, use a material of lower conductivity, play with varying scales of resistors etc. .... Alright, after some calculation, I have you at a resistance of roughly 24.3 KOhms Does that work? I'm sure I've messed something up in a glorious fashion here, as this seemed far too simple. What did I miss? Edited by Casey Wood ##### Link to comment ##### Share on other sites Gosh, I'm probably missing something obvious here but, capacitance is defined as Charge over Voltage, and of-course we can say that V=IR. So if C equals V over IR, it seems like the easiest thing to do is to increase the resistance. Lengthen the wire, use a material of lower conductivity, play with varying scales of resistors etc. .... Alright, after some calculation, I have you at a resistance of 72.9 KOhms Does that work? I'm sure I've messed something up in a glorious fashion here, as this seemed far too simple. What did I miss? Units mixed with symbols? Capacitance is in Farads F. Charge Q is in Coulombs C. Voltage U is in Volts V. Current I is in Amperes A. 1 F = 1 C / 1 V 1 V = 1 A * 1 ohm Substitute: 1 F = 1 C / ( 1 A * 1 ohm ) But we know that I=Q/t, or Q=I*t. In units it'll be 1 C = 1 A * 1s. so 1 F = 1 A * 1s / ( 1 A * 1 ohm ) = s/ohm ##### Link to comment ##### Share on other sites My unit analysis gave (Amps ^ 2 * s ^ 4)/( kg*m ^2 ). This is indeed capacitance. The unit for resistance will be almost identical to the reciprocal, but with s ^ 3. Thanks for checking sensei, I need to adjust my number. ##### Link to comment ##### Share on other sites Yes. But again where in actual practice would the alternator change direction do you think? Because, again, I know of no application in practice where that happens. And again, there is no application where you can't avoid it mechanically. Please answer this so I don't keep asking. You seem pretty intent on your erroneous assumptions, so why would I bother explaining it? You already think you know the answer, obviously nothing I say to you is going to make the discussion go in a positive direction. If you want to know the answer just use your imagination, there's infinite possibilities for physical circumstance, there's all sorts of actions that aren't perfectly unidirectional or that one does not want to restrict to one direction. You're basically just saying "I could be wrong, but I assume I can't possibly be wrong," no point arguing with someone like that. I am not too much experienced with alternators, but in normal electric motors, the faster spinning, the higher voltage. So if it's exactly the same with alternators, which is what I suppose so. Spinning too fast (if there is nothing like regulator), could cause damage of electronics connected directly to it, in certain extreme situations. (Google shows plentiful of pages after searching for "alternator producing too much voltage", so it's real issue). In such situations, voltage threshold triggered branch with zener diodes could be used, f.e. Place fuse in horizontal branch instead of resistor. Zener diodes f.e. 15 V. If voltage is exceeding 15 V, current will flow through zener branch, instead of normal branch, and fuse will blow up, disconnecting entire circuit. Such (or other) security elements should be used in circuits, regardless whether current/voltage regulators are present. They might fail, and you need to be prepared for it in advance. Single zener diode costs here$0.05.

Well, I am dealing somewhat with lower power, but on the other hand there is a chance the rotation could spike up in frequency and maintain that frequency in a certain sense, even when alternating in different directions. Why is it better to use a fuse that could blow up instead of a charge regulator? Just more cost effective?

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Well, I am dealing somewhat with lower power,

What power?

I said voltage..

If you want 5 V, then take Zener 6 V, that's no problem at all.

I used 15 V as an example for protecting 12 V nominal voltage circuit.

Why is it better to use a fuse that could blow up instead of a charge regulator? Just more cost effective?

I was describing general way of protecting vulnerable circuit, used in any case.

Voltage regulators are using Zener diodes to not allow too high voltage reach circuit.

and this

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Why is it better to use a fuse that could blow up instead of a charge regulator?

A fuse will blow and simply stop the circuit working if the current exceeds some limit.

A charge regulator will ensure that the battery is charged with constant voltage or constant current as required by the battery (or whatever charging curve it requires). It will also stop the charging process when the battery is fully charged to prevent damage. A fuse can't do any of those things.

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