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Old 03-17-2009, 04:22 AM
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ZnsaneRyder ZnsaneRyder is offline
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Join Date: Nov 2008
Location: FLORIDA
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Default Re: 12 volt fog lamp as headlight

Originally Posted by Prasinos View Post
Obviously a graph would be ideal but I'm just looking for the maximum output, at or near redline, lets say.

Also, wouldn't it make sense that at higher rpms the engine would need to spark more often? And this higher voltage should cause a more powerful spark, which would basically "self regulate" the voltage supplied by the white wire. As long as the circuit using the white wire had enough resistance to prevent an overdraw of current.

Let me know if this is backwards thinking.
It makes sense, but let me explain......... The voltage changes with RPM, so the amount of voltage is not too important, as long as there's enough there. It doesn't self-regulate, it just has a limit on how much power.

Here's some help......

Use your diodes or rectifier to make DC first. You can also add the capacitor to smooth out the voltage.

LED's are current sensitive, NOT voltage sensitive! LED's have a set voltage drop. You MUST use a resistor with all LED's to limit max current over a desired voltage range. For example, just 3.8V will burn out some 3.6V LED's without resistors!

Typical single 3.6V White LED uses approx 20mA of current. If you use a 150ohm resistor in series, you get approx 20mA from 6V. You could also try 100ohm for 30mA if the LED can take it (more brightness). Even if your voltage goes over 7V, the resistors will keep the LED's safe and protect from overcurrent.

Since you have almost 3 watts of power to use, I'd recommend using 2W or less of total LED's to allow some headroom to keep a strong spark.
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Last edited by ZnsaneRyder; 03-17-2009 at 04:25 AM.
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