Got 0.4 V - What Can I Use It For?

From a little water wheel I can get a fairly constant 0.4 V.

Can I use such a small amount of electricity for anything useful?

cheers all

Not much...you need at least 1V to do anything with it. Even the very lowest voltage boost converters need .5V or more to operate. About all you can do with voltage that low is turn it into heat, & probably not much of that. If you use a mechanical speed increaser, like a belt drive, won't it increase your generator output?

ps ... don't forget about current (besides that of/in the water) .
E X I = Watts (aka : work)

if you measure the current from that generator putting out .4 volts and it is (say) 100 mA ...
increasing the voltage to .8 volts will only give you 50 mA available .
at 1.6 volts this would be 25 mA ... and so on .

"no free lunches"

Another thing to think about is if you are measuring the 0.4 volts at no load.

As you start loading the generator, the generator will start resisting the force of water and start to slow down - further reducing the generated voltage.

Just to experiment, try connecting a 1.5 volt flashlight bulb (from a flashlight that runs on a single 1.5 volt cell) to the generator. You may get a mild orange/yellow glow from it.

25 mA at 1.6V would be enough to dimly run a red LED or something... if it wasn't for the converter issues mentioned by Tekwiz.

LEDs actually start emitting light (dimly) at pretty low currents.

Yeah but if you want to boost that, you need something active. Silicon doesn't start playing until you get to 0.6-0.8V. IMO the best way to boost the output is to get a larger input source: drive the water wheel with a higher velocity, higher pressure stream of water.

Alternatively, add coils to the generator.

-Adam O.

It might be possible to create a germanium-based voltage tripler or quadrupler by utilizing a mechanical switch on the water wheel, but it would require the .4V to remain steady under a bit of load.

Just a thought.

You could use a zero threshold MOSFET to build an amplifier or some other gadget. They will work with power supplies as low as 0.2 volt (and possibly even lower).

http://www.aldinc.com/ald_przerothreshold.htm

I must have been thinking about this or something, because last night, in a dream, I found the answer....

What can he do with 0.4v? Put ten of them in series.

Either that, or switch to an AC generator, so a transformer can be used.

Best idea yet IMO.

Use a "vibrator" (no, not that ) power supply, like those used in old cars to power the anode on tube radios. It consists of a relay, which has one side of the switch connected to the +, the other side connected to one side of the coil, and the other side of the coil connected to the primary of a transformer, and the other side of the primary connected to the -. The power trips the coil, which cuts off power to the coil, then the switch springs back, and the coil is tripped again, creating pulses that can drive the transformer. For 0.4 V, you'll need a sensitive optoisolator instead of a relay.

hmmm ...
what is the Vfwd of the IR led in an opto isolator ?

Oh, besides zero threshold MOSFETs, they also make depletion mode MOSFETs and JFETs. Less common, but they are "normally on". With a typical "joule thief" circuit and a lot of gain (more turns on the feedback winding than the primary), you should get something that oscillates at arbitrarily low voltages (0.1ish?).

Tim

Thanks guys,

Fascinating stuff.

Hmm, never thought of using depletion mode semiconductors. That opens up some interesting possibilities. Such a converter would be very limited power wise, though. At that low a voltage, you'd need enormous currents to produce any reasonable amount of power.