What is the best way to get regulated 12V DC output from my bike generator?
There three ways to get regulated voltage output from a human powered generator:
Keep in mind that to use the GM 1-wire 63 Amp Alternator you need to hook it up to a protective resistor so that it doesn't get damaged when some one gets on and pedals without a load. See instructions how to do this HERE.
Almost anything you hook up in the cigarette lighter of your car is able to run at 14.8 Volts DC. For instance in AC inverter typically has an operating range up to 15 Volts DC. So you could use a car alternator to provide power to an AC inverter which could power a play station video game or X-box video game, or laptop computer, or TV set.
If you absolutely have to have 12 Volts instead of 14.8 DC volts then you can hook up 4 diodes to the output of your alternator / generator. Each diode would drop the voltage down about 0.7 Volts. So the final output voltage of the bike generator car alternator would be
14.8V DC - ( 4 x 0.7 )V DC = 12.0 Volts DC
The important thing to know about picking out the diodes is that you have to get the biggest ones you can because if you have 10 Amps going through them then each diode would be dissipating about 7 Watts. You get this rating from using the formula for power:
Power dissipated in a diode through heat = 0.7 X current
You may not think that 7 Watts is much, but believe me, after 5 minutes of heating up at this wattage, you will get a burn by touching a diode that is not rated for that kind of wattage. If you were to get a T-42 diode with a heat sink then you would be OK.
If you want to look at the data sheet for this part hen click HERE
For example the LT1083CP-12 is a monster sized 12V regulator that you could use. It's less than an inch wide, but it is huge when you consider that it is about the biggest 12V linear regulator sold commercially. Typically a 12V regulator can handle only 1 Amp of current. This one can handle 7.5 Amps. It's max input voltage is 25V DC. This is sold by Digikey for $13.25.
There are a few considerations to take into account when evaluating this option.
You can imagine how much bigger this heat sink would need to be if your pedal power bike generator is putting out a voltage of 20V. That would be (20V -12V) x 7 Amps = 49 Watts. So you would have to buy a heat sink that is 3 times bigger or put a small fan on one heat sink. This is why a linear voltage regulator is SO INEFFICIENT at input voltages much higher than the output voltages, you loose much of your precious energy as it literally disappears into the air - as HEAT!
DC / DC CONVERTER: The DC to DC converter more efficient than a linear regulator for situations when you your bike generator is running well over 12 volts., but is expensive if you want to generator in the 50Watt to 100Watt range. Prices range from $50 to $200.
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