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#Post#: 3737--------------------------------------------------
Buck Boost Idea
By: lynx wind Date: July 6, 2014, 12:16 pm
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I was playing with a simple circuit to Buck voltage from a wind
turbine. Here is a schematic. I'd love to hear comments.
I did try it with a single phase alt and a flat Nicad 12 volt
battery. Instead of the hard to turn thump thump, the alt was
very smooth up through the rpm. Battery voltage rose quickly to
14.89 with a hand turn. If the alternator isn't turned the
capacitor just sits with its voltage. The capacitor is charged
with full wave but only discharged on the half wave when the
power transistor is triggered. So in effect the rpm controls
duty cycle, and creates a square wave (lower volts/higher amps
to load).
Might need to add an RC delay on the base triggering to build
more voltage on the capacitor. That way duty cycle might be
less than rpm at low speeds and fully on each cycle at higher
rpms.
#Post#: 3770--------------------------------------------------
Re: Buck Boost Idea
By: nessprojects Date: July 7, 2014, 6:19 pm
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@lynx
I see your idea and your concept but I think the frequency will
be way too low and you would need a massive coil to get any kind
of gain. 30khz + is the normal for a buck/boost system.
Sorry to say butt......
Just run your circuit in my simulator and it just don't seem to
do anything except half the power to your battery and kept
blowing up the 2n3055 due to base/emitter voltages going beyond
7v.
Remember though this is only a simulator and not the real world
!.
#Post#: 3774--------------------------------------------------
Re: Buck Boost Idea
By: lynx wind Date: July 7, 2014, 7:11 pm
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Thanks guys. Yes, I agree the frequency has to be higher. You
may have noticed I like those power transistors. So why cant we
bias the transistor at a higher rate by feeding the base with a
capacitor through a variable resistor like CG showed? Just blip
a higher voltage at a high rate. In effect letting the turbine
run faster.
The only change to CG's drawing would be to feed the base from a
cap instead of just the rectified voltage off the alt.
I am really old school when it comes to electronics.
#Post#: 3787--------------------------------------------------
Re: Buck Boost Idea
By: lynx wind Date: July 8, 2014, 5:32 pm
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I scrapped the above diagram in favor of the Re-EMF charger by
Rene.
HTML http://youtu.be/lvKa4zneaRQ
HTML http://youtu.be/lvKa4zneaRQ
Basically it allows for a much higher voltage to charge a lower
voltage by chopping the voltage. It's an interesting circuit
because the flyback also charges the battery.
It does work. When I crank the alt the 4000ufcap charges
smoothly up to 20-35 volts and discharges through the 12 volt
battery. I am using a torroid with bifilar 18 awg 40 turns.
One or Two 2N3055 transistors in parallel. 4000uf 35 volt
capacitor.
I am not so great with electronics so this circuit may only be
good for 10 watts. I may be way off.
#Post#: 3791--------------------------------------------------
Re: Buck Boost Idea
By: lynx wind Date: July 9, 2014, 8:16 am
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I'm only using one bridge from a scrapped circuit from a 3 phase
experiment.
Cutin is just as it would be without this circuit. Amps build
as soon as voltage exceeds battery voltage. I was using an old
alternator from past experiments so I can't compare rpm to any
other alt..
Yes, I have tried it with an aircore and the ferrite helps. You
can use a rod, or a choke as well as a torroid.
The next thing I will try is a variable resistor and maybe a
diode in front of the base and make adjustments. The only
difference between this and just a rectifier, is there is a
smooth feeling turning the alt and rpm can go higher. The
capacitor can run at a much higher voltage than the battery
being charged.
I am pretty sure the electronics guys will tell me this is a
dead end, but it's fun to try.
#Post#: 3793--------------------------------------------------
Re: Buck Boost Idea
By: lynx wind Date: July 9, 2014, 9:06 am
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That's the idea. Yes this can be paralleled with the
NessProjects boost. But the boost will have to be a separate
circuit to the battery being charged.
I'm a broken record.....you can't get more power in a low wind
area than there is.
#Post#: 3796--------------------------------------------------
Re: Buck Boost Idea
By: lynx wind Date: July 9, 2014, 10:06 am
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After drawing the circuit I realized the boost has to be inline
and just for trickle charge. It needs to be bypassed at 5-10
watts.
Here is what I am thinking. The only issue I know is suspect is
the duty cycle control. This oscillator will probably ring
instead of making a nice controlled square wave. Ideas on
solving this?
#Post#: 3801--------------------------------------------------
Re: Buck Boost Idea
By: nessprojects Date: July 9, 2014, 4:40 pm
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The addition of rene`s circuit in the system would be a good
idea....It would act to de-sulphate the battery as well as
charge. As stated it still needs something to by-pass the bulk
power....Hmmm
#Post#: 3805--------------------------------------------------
Re: Buck Boost Idea
By: lynx wind Date: July 9, 2014, 7:06 pm
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I mounted everything. I added a red diode to the base and a 5k
ohm pot in line with a 200 ohm resistor. It allows for very low
oscillation up to very high. With high resistance it easy to
turn the alt up to 24 volts on the cap and rapidly charge the
load. The boost allows for very low rpm charging.
I'll make a video showing the input voltage and the load battery
voltage.
The red LED is a nice way to visually see the charge rate. This
is still very crude and probably not a great idea, but it kind
of does what I want, or where we should head.
#Post#: 3812--------------------------------------------------
Re: Buck Boost Idea
By: lynx wind Date: July 10, 2014, 9:29 am
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Ness,
Can I substitute a Mosfet in place of the power transistor?
Gate to my led/resistor - Source to battery negative - Drain to
torroid coil?
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