Low power switching

[tomc]

I am a beginner at electronics and am trying to create a circuit to use small frequently-polarity-switching induced currents to generate a constant current flow for power generation reasons.
I understand that if I use a conventional rectifier circuit the supply voltage must be larger than the 0.7 volt drop caused by the diode. I think I will also have this problem if I use a microcontroller and BJT. Also if I use a "precision Rectifier Circuit" which utilises an Op Amp I will have to power the op amp, thus reducing the power generated.
Does anyone know of another solution or have any ideas for this problem?
Thanks
Tom

[audioguru]

Hi Tom,
Welcome to our forum. ;D
Do you have a low voltage generator and want to rectify it into DC with low loss?
Then step-up its voltage with a transformer like electrical utility companies do, then the 0.7V drop of each rectifier diode is negligible.

[tomc]

Thanks very much for your prompt reply.
Forgive my ignorance but I'm not 100% confident in my understanding of voltage/current relationships.
The  power is generated by sliding a coil of wire in and out of a magnetic field. I understand this generates a current in the wire but I'm not sure about the voltage behavior.
Could you recommend something for efficient utlisation of the small amounts of power generated in ths manner.
thanks again
Tom

[audioguru]

Hi Tom,
It sounds like you are making a dynamic microphone that is like a speaker with a moving coil in a magnetic field. Its power output is extremely low.

Maybe you are making a "shaker" flashlight where you shake its magnet up and down inside a big coil and if you shake it long enough then it charges a rechargable battery or huge capacitor to light its dim LED for a few minutes.

Perhaps you should look at the many wind-generator websites for efficient power generation ideas. A good generator is a lot more sophisticated than sliding a coil in and out of a magnetic field. ;D