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Unread 22-02-2009, 19:03
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Re: Wiring Lightswitch and LED (Driver Station

Yes. But... maybe you should consider the LED you will use: Different colors need different voltages.

Calculate the resistor value by knowing Ohm's law (V=I*R), the voltage requirements of the LED and the current requirements of the LED (do NOT use the maximum LED current, use something quite a bit less. For example, 20 mA is a good value for almost all LEDs) and the voltage supply (from the driver station in this case). So, if your LED needs 2 volts, and you have a 5 volt source (the driver station), your resistor has to drop 3 volts. If your LED wants 20 mA, your resistor is (V/I = R, 3 / 0.02 = 150 Ohms, so anything from 150 to maybe 270 Ohms is OK (about a 2 to 1 ratio). So maybe my first answer, a 680 Ohm resistor, might be a little bit large (it is appropriate for a 12 volt source). It would be OK, but the LED might be dimmer than you prefer.

You can also check if a 1/2 watt resistor is enough by using Watt's Law: P=I*V, so (3*0.02 = 0.06) or 60 milliwatts, so 1/2 watt is way overkill but that's never a problem. (It's bad when you try to dissipate 1 watt with a 1/2 weatt resistor - it 'overheats'.)
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