BIGD53
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Wind Turbine: possible power supply

Sun Jan 20, 2019 9:13 pm

Hello Raspberry pi community,

I am trying to make a wind turbine that could possible power my raspberry pi and even charge a battery for later use. I have the fan blade, but I'm stuck on witch motor I should use to get the best power.

Thank you,
Big:D

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Imperf3kt
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Re: Wind Turbine: possible power supply

Mon Jan 21, 2019 12:17 am

You'll need a lot more than just a fan blade turning a motor.

As I understand it, you should check if you need a transmission system (one large pulley on the blade, one small pulley on the motor, a belt between)

From there, the motor acts as a generator, producing unstable voltage depending on the wind. The current is probably very low unless the turbine is large. (ever seen a wind farm and how massive they actually are?)

To be able to use this voltage, you need to regulate it. Connect the motor up to a DC regulator module that can take a wide input voltage range - you'll have to measure extremes before deciding.
That should output a stable voltage at x amps. X being unknown, dependant on the wind and your turbine.

Use that stable voltage to recharge or trickle charge a battery, which in turn powers another regulator that powers the Pi.

You also need to ensure the battery doesn't overcharge nor over discharge.

So you need:
Turbine blade
DC motor, possibly geared or w/ pulley setup
Heavy gauge wiring
Solder (plus tools)
Wide input range DC voltage regulator
Battery (lead acid is probably your best choice)
Overcharge protection circuit
Over discharge protection circuit
Second regulator to convert the battery power, to the correct voltage and amperage for the Pi
A way to monitor battery state and cleanly shut down the Pi before over discharging the battery (it will not run 24/7)
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BIGD53
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Re: Wind Turbine: possible power supply

Mon Jan 21, 2019 12:34 am

Thank you so much. If I could simplify the set up to something like this(https://youtu.be/AckRAYQ8N48) would it still work? I would still have to program the pi to shut off at a drop off of voltage.

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Imperf3kt
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Re: Wind Turbine: possible power supply

Mon Jan 21, 2019 1:26 am

If you watch the video to the end, you'll see they used everything I mentioned except a battery and it's related protection.
They did add an AC to DC rectifying diode, possibly because the specific motor they were using generates 3 phase AC, not DC, but you will also see the voltage swings wildly between 5v and 18v.

A Pi wants 5v and 5v only, so a regulator is added, which they have done in the video.
However, they only charged a mobile phone with it. Presumably because such a setup is unlikely to deliver the several amps something like a Raspberry Pi requires.

I suggested a battery because what do you do if the wind stops blowing?
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Gavinmc42
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Re: Wind Turbine: possible power supply

Mon Jan 21, 2019 7:50 am

Try with a stepper motor instead of a brush DC motor, works better at lower RPM.
Rectified and capacitor smoothed and charge a battery then 5V SW regulated.
Powering it directly is asking for trouble, wind power is not very reliable unless you live in a location that is windy all the time.
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Imperf3kt
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Re: Wind Turbine: possible power supply

Tue Jan 22, 2019 4:38 am

Gavinmc42 wrote:
Mon Jan 21, 2019 7:50 am
Try with a stepper motor instead of a brush DC motor, works better at lower RPM.
Rectified and capacitor smoothed and charge a battery then 5V SW regulated.
Powering it directly is asking for trouble, wind power is not very reliable unless you live in a location that is windy all the time.
My google-fu tells me the opposite, stepper motors produce no useful current at low RPM.

What you want for maximum simplicity, is the cheapest motor you can buy - a brushed DC motor.
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maurice1
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Re: Wind Turbine: possible power supply

Tue Jan 22, 2019 7:51 am

Would an old alternator from a small car with a 12v battery and buck converter be an idea?

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Imperf3kt
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Re: Wind Turbine: possible power supply

Tue Jan 22, 2019 8:25 am

Provided the regulator inside the alternator works, maybe. Alternators are 3 phase AC - something I was unaware of until a recent disagreement with another forum member.

But I imagine the alternator will need more force than wind can put on it.
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BIGD53
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Re: Wind Turbine: possible power supply

Wed Jan 23, 2019 10:30 pm

I have heard that PMA motors work the best for small wind turbines. Since it spins around a magnet it produces more power with less RPMs.

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Gavinmc42
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Re: Wind Turbine: possible power supply

Thu Jan 24, 2019 10:22 am

The multipole motors in Fischer Paykel are popular.
Smaller are the multipole ceiling fan motors.
A google will find designs using these and suggested coil configurations and rewinds

The more poles the better as wind generator are low speed devices.
Step up gearboxes cause noise and mechanical issues, but magnetic gearboxes are looking promising.
I'm dancing on Rainbows.
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mahjongg
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Re: Wind Turbine: possible power supply

Sat Jan 26, 2019 3:48 pm

Note that no RPI has a rechargeable battery, like the smartphone in the youtube-video has. It requires a *constant* 5V @ (say) 2A. no interruptions allowed.
The Conclusion must be that the energy (wherever it comes from) must first be stored (in a battery) before it can be used to power a PI.
also realise that every conversion step (wind-turbine->battery-charger->battery->voltage-converter->RPI) introduces some energy losses, so at the end most of the energy the turbine (or whatever the energy source you use is) won't make it to the RPI.

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mahjongg
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Re: Wind Turbine: possible power supply

Wed Jan 30, 2019 11:18 am

Note that instead of a battery, with finite charge discharge cycle life, you could also use a large supercap (several farads at least) with protection electronics, to prevent overcharging, and chargebalancing, if you use several supercaps in series for a higher voltage (than the standard maximum of 2.7V or so).

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