Hi Experts,

Like to know, I got 12V 4500rpm DC motor, which I'm using as Generator by manually rotating it's shafts, & connected it's output to full-wave bridge rectifier & 1000microF capacitor at output, but I'm getting fluctuating output of 1V, kindly let me know what all other components (with values) are required to make output stable,

Thanks in advance
Ashish Bhatia

 

First a question: Is this a permanent magnet DC motor, or is it a series field type of DC motor? Also, what speed are you rotating it at? Turning a motor by hand, even with a crank, provides a rather uneven speed. And a generator output is very dependent on speed.
At the speed that most folks can rotate a motor by hand, one volt is a very reasonable output. So the major components to make the output voltage more stable will be an arrangement to make the rotation speed higher and more constant.

 

First a question: Is this a permanent magnet DC motor, or is it a series field type of DC motor? Also, what speed are you rotating it at? Turning a motor by hand, even with a crank, provides a rather uneven speed. And a generator output is very dependent on speed.
At the speed that most folks can rotate a motor by hand, one volt is a very reasonable output. So the major components to make the output voltage more stable will be an arrangement to make the rotation speed higher and more constant.

Thanks for suggestions, it's a permanent magnetic dc motor, also I'm making a project in which it needs to rotated via hands, kindly let me know, what other components can be added to make it give stable output,

Due to slow speed only, I'm asking question in this forum, else with RC circuit, it's output can be stabilize, but it's not working,

Kindly support

 

The output voltage will depend on the speed you are driving the motor. To get about 12V you will need a mechanical gearbox to increase the speed of your hand crank up to about 4000 rpm to drive the motor.
The losses in the gearbox at that ratio may make the crank very hard to turn!

 

IT is difficult to stablize a voltage not generated. At the very least you will need a good crank arrangement. You will need at least 100 RPM to get anything useful out. And that won't be a whole lot.

 

Like to know, I got 12V 4500rpm DC motor, which I'm using as Generator by manually rotating it's shafts, & connected it's output to full-wave bridge rectifier

"connected it's output to full-wave bridge rectifier"
Why ??

 

What are you hoping to use the stabilised voltage for? How much current does it need?

 

Hi Experts,

Like to know, I got 12V 4500rpm DC motor, which I'm using as Generator by manually rotating it's shafts, & connected it's output to full-wave bridge rectifier & 1000microF capacitor at output, but I'm getting fluctuating output of 1V, kindly let me know what all other components (with values) are required to make output stable,

Thanks in advance
Ashish Bhatia

A massive flywheel

 

It is a DC motor and so the voltage when you turn it will be DC. Polarity will depend on which way you spin it. What is the application, how much voltage and current does the application require??? The answers are rather important.

 

A massive flywheel

There are many treadmill FW's where the motor user has discarded it.
It will however present a very heavy load for a small motor, so any use would require a VERY slow accel.

 

There are many treadmill FW's where the motor user has discarded it.
It will however present a very heavy load for a small motor, so any use would require a VERY slow accel.

He's using it as a generator.

 

The hand driven generators that I have seen all use a gear set to increase the speed. So that is the first requirement, mechanical, not electrical. The a simple diode to charge a capacitor. BUT, once again, what is the desired application and how much POWER does it require?? The crank powered radios require about 6 RPM cranking which is geared up to a few hundred RPM. generating.

 

"connected it's output to full-wave bridge rectifier"
Why ??

My project requirements is to rotate motor in both directions manually, so getting + & - Voltage at output, that's why connected it to Bridge rectifier

 

It is a DC motor and so the voltage when you turn it will be DC. Polarity will depend on which way you spin it. What is the application, how much voltage and current does the application require??? The answers are rather important.

Voltage required 5V, current required 1A

 

So all you are maintaining is the same polarity output regardles of rotation dir ??
IOW, steering diodes.

 

Rotating a motor back and forth is not likely to provide enough speed to deliver much voltage, and certainly not much power. How about explaining the operation and the goal?

 

Yes

So all you are maintaining is the same polarity output regardles of rotation dir ??
IOW, steering diodes.

Yes

 

Rotating a motor back and forth is not likely to provide enough speed to deliver much voltage, and certainly not much power. How about explaining the operation and the goal?

As mentioned earlier, output voltage required is 5V & current 1A, goal is to charge device like mobile phone

 

As mentioned earlier, output voltage required is 5V & current 1A, goal is to charge device like mobile phone

OK, I recall that!
The brutal reality of basic physics is that the electrical power out of any generating system can not exceed the mechanical power input. So for five watts of electrical power supplied there must be at least five watts worth of mechanical power provided. And with the efficiency being quite a bit less than 100%, the actual input must be greater than that.

 

My project requirements is to rotate motor in both directions manually, so getting + & - Voltage at output, that's why connected it to Bridge rectifier

At what speed? (RPM)

How often does the direction reverse?

Why can you not rotate it constantly in one direction?

Why won’t you explain the mechanical design?

If you want help, you need to tell us exactly what you are trying to do.