Ohms law

 invaluable when dealing with electricity and power.



Ohm's Law is often remembered as a triangle. Simply cover up the letter representing what you want to find and use the equation it shows.

I remember the above triangles representation as WIVVIR or 'with her', works for me.

W = Wattage     I = Current   V = Voltage   R = Resistance


I need to know what current my 11 watt bulb is drawing from the battery?

Therefore 11 watts divided by 12volts = 0.9 A (or 900 mA)


How much power is my dc motor using?

3 amps multiplied by 12 volts = 36Watts




Most of the wind generator projects on this site produce alternating current (AC), fine for lighting small bulbs, but for powering LED's, electronics or

charging batteries a more useful direct current (DC) is required. The most basic form of rectification is the use of a silicon bridge rectifier.



There are several ways of connecting diodes to make a rectifier to convert AC to DC. The bridge rectifier is one of them and it is available containing the four diodes required.

Bridge rectifiers are rated by their maximum current and maximum reverse voltage. A 1 Amp 50V (Code W005 from Maplin) is suggested. Cost 18 pence!

Be sure to insulate all connections with insulation tape or even better mount on a small piece of veroboard.

Alternatively four 1N4001 diodes wired as in diagram below has the same effect.



Wiring up your Solar /Wind battery system



Inline Fuse for safety




A Fuse connected on the positive line is advised when connecting any charging system either solar or wind powered. You can use either the inline type

or blade type as found in vehicles, I use a 1 amp fuse with the dynohub and my 5w solar panel, higher values required for the 100w generator (10A)


Blocking diode



Diodes prevent electrical currents from discharging back into your wind generator and prevent 'motoring' on windless days. It will prevent your solar battery's

electrical currents from discharging back into your photovoltaic power system at night or on very cloudy days. The stud type 40 amp blocking diode above was mounted

onto a heat sink from an old amplifier, such diodes can be found on eBay for a couple of pounds.

Note: a blocking diode is not required for the dynohub wind generator.


Charge control



Personally I don't use any charge control systems, they are available but beware - solar power regulators, only disconnect the generators load at about 14 volts, fine for solar panels, but for wind generators this would cause the generator to become 'unloaded' and cause the blades to spin to a dangerous speed. charge controller's are available, but expensive, see my charge controller for solar panels only. here.

 I simply measure the battery's voltage regularly with my digital multimeter and when it hit's 14 volts, I 'tap' some power off the battery e.g a 12v compact fluorescent lamp.



The amazing 'Watts up' power Meter


This Watt Meter is a high quality all in one instrument, it replaces an ammeter, voltmeter, wattmeter, Amp-hour and Watt-hour meter.

Simply Connect it between a power source and a load and you can measure all the important electrical parameters.

It is not cheap, approx 48 but a very useful monitoring device for both wind and solar power. more here




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