i'd like to start by introducing myself,
my names nick and i like to tinker.
to the point, I'm looking to build a circuit that can capture low ac voltage (.1v-5v ac) from an induction generator and turn it into dc volatage (10v dc).
efficiency is veryyyyyy important.
I have very little electronics experience, although more than the average but I think something using mosfets would work or maybe a full wave rectifier diode...
any help is greatly appreciated.
-Nick
what i'm trying to do in short is harvest small amounts of energy until the stored capacity grows to a point that is useable for powering a device for a short amount of time.
Ronsimpson's references are good for turning low voltage DC into higher voltage DC. But before that there is the problem of efficiently converting the AC to DC. The obvious solution for that is to use an efficient transformer to raise the voltage to the point where Schottky diodes or MOSFETs used as rectifiers can be efficiently used.
What is the lowest frequency of the AC from the generator and what is its current?
I understand. at its lowest the voltage will be 20mv at its highest it will be 4 volts. when the generator is operating normally around 2-3 volts at .01 amps.
the idea I have is to capture the energy like coins in a coinbank. over time the charge will build to a point it is useable.
A joule thief circuit will convert 0.6v or so to a higher volatge, usually only 70% efficient, do a google for joule thief, if you want nore efficiency than this then you'll need some in depth electronics knowledge.
DC to Dc upconconverters I've seen in ic form start working at 1v, a blocking oscillator joule thief type circuit with a singlee transistor assuming silicon is used will start working around 0.6v, maybe a little less, germanium transistors (only good for low power) will start to work around 0.3v, maybe a little less.
Not sure what you mean by frequency. can you clarify? are you asking the hz? that is variable as its a bouncing magnet moving through insulated copper wire.
would it be easier to first up convert the ac to higher voltage ac before converting it to dc?
So it is like a "shake flashlight".
The LTC3109 in post #3 clams it will work to 30mV and auto sense polarity which might be like "AC". I have seen it work at 50mV.
If you could run form 0.5 to 5 volts then I know another way to do that.
This will probably not work for you but there might be an good idea in it.
I have a high voltage low current source. This does work. The diodes loose 0.4 volts.
In your case it will convert the AC to DC. Then store anything above 0.4 volts on a capacitor.
The DC to DC converter will make a regulated supply for running a micro computer or small radio.
If there is more energy than needed the power is stored for later use.