light bulbs according to available voltage

[doronb]

hello you gurus....
i am definitely not an elctronics person, as i have studied just the basics of it but i wish to buils a basic project that will work like this :
i will have voltage source (alternator) that will me different voltage according to the rotating speed.
i wish to light bulbs (3v ones) according to the rotating speed, thus, according to the available voltage.
i have two questions :
1. does a primitive alternator supply voltage according to its rotating speed indeed ?
2. i have been thinking of a circuit that uses transistors to control the amount of bulbs that will be lit according to the available voltage.
if T1 opens in 3v, and T2 opens in 6v and T3 opens at 9v etc....
will it work ?
(i must admit that i do not understand anything about transistors so it might be that i have BIG missconception...)

and extra question : will it be possible to produce something like this but not in line, but in parallels so if a bulb gets burned it does not influence the rest ?
thanks a lot,
doronb

 

[rezer]

hello you gurus....
i am definitely not an elctronics person, as i have studied just the basics of it but i wish to buils a basic project that will work like this :
i will have voltage source (alternator) that will me different voltage according to the rotating speed.
i wish to light bulbs (3v ones) according to the rotating speed, thus, according to the available voltage.
i have two questions :
1. does a primitive alternator supply voltage according to its rotating speed indeed ?
2. i have been thinking of a circuit that uses transistors to control the amount of bulbs that will be lit according to the available voltage.
if T1 opens in 3v, and T2 opens in 6v and T3 opens at 9v etc....
will it work ?
(i must admit that i do not understand anything about transistors so it might be that i have BIG missconception...)

and extra question : will it be possible to produce something like this but not in line, but in parallels so if a bulb gets burned it does not influence the rest ?
thanks a lot,
doronb

The alternator voltage will swing a bit depending on the speed of the alternator. This is due to the output frequency which is based on the rotor speed, but I don't know if you will get down to 3V. At lower speed, you can expect less ripple but more of a ramping effect on your output.
I would use the lamps in parallel with a resistor in series for each bulb. Use ohms law to calculate the resistance that you need based on a 15V supply (Vbulb/Rbulb = Ibulb. Vr / Ibulb = R). It would be better to use a comparator to control the lighting of the bulbs based on the output voltage of the alternator. If this is not enough I can expound further.