Hi,

I was trying to use a impeller connected to a 3 V DC motor to light a LED (red). The output voltage from the DC motor (due to wind) is intermittent and varies between 0,2 V to 1 V. The LED does not light up as it need minimum 1,5-1,8 V. Is there someway i can use 100 microfarad capacitors, NPN transistors and simple diodes to make a circuit where the voltage from the motor slowly charges up the capacitors and when the capacitors have sufficient voltage, they automatically discharge across the LED to light it up?

Regards,
Singh

 

A typical off the shelf, common red LED will require about 1.8 to 2.2 volts and typically about 20 mA of current. They will generally illuminate dim with a lower forward voltage and current. No combination of capacitor, transistor, or other parts will work. Your cap will only charge to the voltage you have, that is as good as it gets and I doubt a boost converter will get you anywhere. Using your DC motor as a generator how much current can you get?

Ron

 

Here's a video using a 5V motor and some serious gear ratio increasing the rotation of the permanent magnet motor. It's titled "Free Energy - NOT!" because there's no such thing as making energy out of nothing. In the video I use muscle power to spin the large gear which in turn spins smaller gears even faster. The result is the motor spins with sufficient energy to light a Super Bright LED (SB LED). The SB LED takes close to 3 volts (3Vf or 3 forward volts) to light up. Clearly I'm generating enough energy to light the LED's but if you want to do the same thing you're going to need a way to spin the motor sufficiently fast in order to do that. The amount of force needed to spin the motor (generator) is unmeasured but I can tell you it takes a bit of work. Having a wind turbine do the same thing will require a sufficiently sized turbine. Otherwise you might need gale force winds just to get a little light out of it.

 

I had one in my garden for some years. It was using a motor from a CD drive if I remember correctly.
The motor you have is not suitable.

I just found it again!

It has a 3D printed propeller around 20cm diam.
The motor is dead now, too many years in the rain. Maybe a new one would be a good idea and set it up again! And this time, a high intensity LED for more light?

 

It was using a motor from a CD drive if I remember correctly.

That's what I have in the video. It's the shuttle motor that moves the laser lens back and forth while the CD spins on a different motor.

 

I am guessing that the shuttle motor may be a stepper motor. Not the best generator for the task.
In addition, because the motor is a DC motor it would only charge capacitors up to it's voltage. You really need a higher voltage motor. LEDs will illuminate some at lower voltages and less current The 20 mA is the highest current allowed to still have te claimed LED lifetime. Always trying for the 20 mA is a bit like trying to drive your car getting the rated horsepower out of the engine all the time. Not a good plan.

 

I am guessing that the shuttle motor may be a stepper motor.

Nope. Just a DC Perm Mag Motor.

Not the best generator for the task.

I agree. Steppers don't make great generators.

You really need a higher voltage motor. LEDs will illuminate some at lower voltages and less current

Seems they light well enough. Those are SB LED's. I'm not 100% sure the motor is a 5V motor, it came out of a tape deck & CD player. The motor COULD be 12V. And I don't much feel like testing it right now. Either way, a 3.3V DC Perm Mag Motor won't fit the bill very well, if at all.

 

FYI, this is the propeller I used..
https://www.thingiverse.com/thing:4941

 

That website in the link of post #8 was moore aggressive than I want to deal with.

 

Use a "joule Thief" circuit to boost the voltage.
Google it.


You can light an LED from 1 volt with this circuit.

 

Put the capacitor across the motor to charge the cap to light the led. You'll need a fast wind or a better motor for the task.

 

i thought a dc/dc voltage booster circuit could work... with a inductor and a capacitor.... need to get a 10mH inductor and a 10mF capacitor though.... also was thinking for intermittent switch could use sort of a flapper... wind will make it vibrate and cause the switch to turn on/off....

 

I had one in my garden for some years. It was using a motor from a CD drive if I remember correctly.
The motor you have is not suitable.

I just found it again!
View attachment 348240
It has a 3D printed propeller around 20cm diam.
The motor is dead now, too many years in the rain. Maybe a new one would be a good idea and set it up again! And this time, a high intensity LED for more light?

3D printed! I have to get a 3D printer and drill press.