hi all! i need some help/advice with a project that i am doing. essentially, i am building a simple wind generator using a PC DC motor. Using a multi meter, i was able to measure the current generated.
lets say i want to charge a 5v battery pack, can i just plug the two wires from the generator into the battery terminals? i know i need a charge protection circuit, thats why i am using a battery pack, as i know there are protection circuit built into it.
i have uploaded a picture, i am sure there are errors, but thats the rough schematic that i can think of. how can i regulate the output output of the generator so that i can charge the battery?
Also, is it possible to charge the battery pack without a constant voltage/current ? any suggestions in modification is greatly accepted =) basically i just want to charge a battery pack using the PC fan as a generator thanks =_)
each type of battery needs to be charged in a different way. some need constant current, some use voltage,
you will need to make or get a charger for your battery. there are lots and lots of charging circuits.
if you only want to charge a nicad, you can buy a solar lawn light for a dollar with integral charger and solar panel.
swap out the solar panel and connect your 'generator'
If you just connect the generator and battery together as you have drawn it, what you have is essentially an electric fan.
I don't know what sort of battery you're looking at that has internal protection, but the fact that it needs it is enough to suggest that this is not a battery that you should be taking liberties with. You will certainly need a charger between the generator and the battery - what sort of charger you need would depend on the battery type.
The voltage output by your generator will vary hugely depending on the wind speed. In order to avoid wasting energy when the voltage is not what the battery requires to be charged, you could use a boost/buck converter.
How much power do you expect to get out of a PC fan? Do you normally have high winds?
I've see where someone used a YAWT to turn a direct-drive (not geared) stepper from an old 5 1/4 floppy drive but he measured the 16+ volts with no load as he turned the YAWT by hand.
hi, well, i dont expect much, probably 2.5 W hahaha i just want to try (for now), to obtain a steady 5V 500mA to charge a battery pack. i need to know how to design the circuit for that.
That looks like an adequate LiPo charger but as far as I can see it assumes a regulated 5V supply. You would need an external buck/boost converter to convert the variable output from your generator to 5V.
A lot depends on how much you aim to do with this.
Suppose that you have four NiMH AA rechargeables.
That particular battery pack is <4.9V empty, >5.3V full.
You want to find out similar for your own battery.
Suppose that the wind gen is <30mA (you never said??)
If it might make more than that then look up "constant current source with one npn bipolar transistor" for how to make a 30mA limited current supply.
an "overflow" of two blue LED series connected and next to the battery will
do nothing while the battery is charging from 5 to 5.2V
light up blue when 5.2V is exceeded
get brighter to prevent overcharging above about 5.6V
You probably want to look up
"maximum power point trackers"
"constant voltage linear regulators" or preferably "buck pwm voltage regulators"
Which PC component did you raid?
If it was the cooling fan, you might find that better suited to making a volt or two to go through the circuit board in a solar garden lamp into a single AA.
I'd suggest using a mosfet between the windmill and battery (control current to the battery) and some type of sensor to detect the rotation speed of the windmill. When you sense that the windmill is spinning at a good pace just switch the mosfet on to start charging the battery. Eventually you'll want to tune it so you're switching the mosfet on and off frequently to keep the windmill turning at a stable speed.
...speaking of fans, be careful using a fan to create the wind to test your windmill. A fan creates a very turbulent airflow and makes it look like your mill isn't working properly.
hi all, thanks for the reply, i remeasured the output by blowing into the blades, and produced roughly 2v and 30 mA at max speed. can a buck converter boost that voltage? if i can use a 5v voltage regulator, would it work?
If it was the cooling fan, you might find that better suited to making a volt or two to go through the circuit board in a solar garden lamp into a single AA.
yeap, it is a cooling fan. so i should use a solar garden board? is there a possibility of bumping it up to 5v?
hi all, thanks for the reply, i remeasured the output by blowing into the blades, and produced roughly 2v and 30 mA at max speed. can a buck converter boost that voltage? if i can use a 5v voltage regulator, would it work?
If it was the cooling fan, you might find that better suited to making a volt or two to go through the circuit board in a solar garden lamp into a single AA.
yeap, it is a cooling fan. so i should use a solar garden board? is there a possibility of bumping it up to 5v?
A useful wind turbine needs to be 4 to 10 times that size - even then they are probably not worth the money.
i agree haha, but this stage is just a prototype, i want to make sure i know that the circuit works before is start investing in something bigger. i came across the schematic for the garden solar board, and apparently, all i need is a shotcky diode if i replace the solar cell with a generator
Have you tried connecting that fan to a 4.5v, 5v or 6v battery and (assuming the battery causes it to rotate) then see can you make it reverse direction by blowing through it. And if you can make it reverse direction then measure the current flowing into the battery.
And don't try this unless you have the approval of your family doctor - I am not taking responsibility for a heart attack.
You need an efficient boost/buck converter with a low quiescent current.
A cheap one from e-bay this one is about 18mA which is a good percentage of what you'll be generating.
I made a turbine using 4 x PC fans, in a decent wind it would generate enough power to run 1 x PC fan at a little more than half speed. Not very efficient but it worked. Much better at charging 2 x AA batteries, then using a joule thief to power a 1W LED.
Used a 5 gallon bucket for the head, rope tied to top hole and a tree branch, another rope tied to bottom hole and a concrete block on the ground.
DMond:
yeap, it is a cooling fan. so i should use a solar garden board? is there a possibility of bumping it up to 5v?
If you can find a friend or relative with one more solar garden lamp than they really want, those are great to take apart because they usually contain
one cheap AA NiMH battery
one battery holder for it
a circuit board of about 1x2 cm to convert "a few" mA from "any" low voltage at the solar panel (0 to 10mA 0 to 2 Volts is typical) to what the battery recharge management controller wants and a nocturnal "any to 3V" converter to run a white LED at about 10mA 3V off a lower battery voltage. And its too small to kill you.
A buck converter can never get 5V from less than 5V input.
Did you mean a boost converter? Beware, as those only work as intended if your supply can deliver at least as much power IV as demanded. The micro oscillator in the garden lamp circuit might be more reasonably sized to what you are doing.
Puzzle:
given how small the capacitors and inductors must be to fit under the epoxy bump, what sort of internal frequency would the garden lamp circuit need to process 5mA 3V?. What sort of current might get an audible (0.3 to 3 kHz)? What R should draw that current at 3V?
DMond:
hahaha doesnt sound very safe....what is the reason for this may i ask?
To give you a real-world impression of how hard it is to generate useful energy with such a small fan.
Maybe blowing into it is not realistic. Try holding it up as high as you can outdoors in a breeze. My guess is it won't generate enough to overcome the charge in the battery.
