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Old 09-08-10, 08:27 PM   #6
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3 pcs 1W Star LED, rated at max 3.3V, $3.20
Star LED

1pcs LM317T voltage regulator, TO-220 type, 1.5 amp design current, $0.65
LM317T LM317 - 1.5A Adjustable Positive Regulator
LM317 datasheet
Linear Series - Voltage Regulators

1pcs R220R12W 220ohm 1/2W 5% Carbon Film Resistor, $0.15 for 10
Resistors 1W

1 pcs TRIM5K 5K 1/4W Min. Horizontal Pot, $0.15

The voltage regulator circuit is shown on this pdf, on page 1.
LM317T Datasheet

Note that when looking at the LM317, the left pin is Adj, the middle is Vout, and the right is Vin.

To make the voltage regulator, connect the 220 ohm resistor between the Vout pin and the Adj pin. Connect the 5k variable resistor between the Adj pin and ground. Connect a 12V (nominal) battery power positive to the Vin pin, and negative to the ground.

The output voltage positive is at Vout, negative at ground. Adjust the variable resistor to get a voltage of just under 9.9V, which is three times the maximum voltage of the LED. The resistance is about 1400 ohms, but measure the voltage output.

Use 14 gauge solid insulated wire to connect the LEDs. This stiff wire allows the LEDs to be aimed as needed. There are positive + markings and negative - markings on the star LEDs. Connect the three LEDs in series, positive to negative. After making sure the voltage regulator output is not above 9.9V, connect the outer LEDs to the positive and negative output of the voltage regulator.

The light output of the three 1W LEDs is about equivalant to a 40W bulb, maybe a little less, and they use about 4W. Be aware that the LEDs and voltage regulator get hot.

Last edited by skyl4rk; 09-08-10 at 09:03 PM..
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