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Didn't see this post come up before now. Was there a delay somewhere? Anyway, to answer your question - do NOT connect an LED directly to a power source unless it is the type that has a built in resistor, and most LEDs do not. It will burst forth in a blaze of glory and then shine no more - ever. Do not run it from AC (the accessory terminals on your power pack) unless you put a standard silicon diode in series with the LED and a resistor to block the AC half cycle that works against (and can damage) the LED. Also note that when doing this, the cathode of the LED must connect to the anode of the silicon diode so that the current flows through both on every half AC cycle. Always place a resistor in series with the LED. The resistor should be chosen so that its ohms value is (source voltage minus 2 volts) divided by desired current in amps; and it's wattage rating equal or greater than the desired current in amps times desired current in amps (again) times ohms value. Or figure the wattage by (source voltage minus 2 volts) times (source voltage minus 2 volts) again divided by resistor ohms value, same thing. Or a third way for wattage which wil give the same answer - (source voltage minus 2 volts) times desired current in amps. This desired current is generally 5 to 20 milliamps (which is the same as 5 to 20 thousandths of an amp), also expressed as .005 to .02 amps. Example - we have a 12 volt DC power source. It can be the DC output from your power pack if you want the throttle knob to control the LED brightness (you probably don't want this, but that's what will happen). Take 2 volts off the 12 to give 10 volts. Do this since the LED itself takes from 1.5 to 2.2 volts to operate, this voltage is not across the resistor itself so doesn't come into the resistor calculation. We average the possible 1.5 to 2.2 volts into a nice easy to handle 2 volt average. We want 10 milliamps or .01 amp to flow through the LED and the series resistor. 10 volts divided by .01 amp is 1000 ohms. Now the wattage rating so the resistor doesn't burn up. From the first method, .01amp times .01amp times 1000 ohms is .1 watt. Second method - 10V x 10V / 1000 = .1W Third method - 10V x .01 amp = .1W Hope this helps.
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