Led Project
05-09-2010, 09:15 PM
#11
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check his links dude. you have to know the specs of the items he is using.
FV on the eight can be 1.7v - 2.2v. the one blinking led can take 10v directly, and is 70mA. the other blinking one is 3-5 forward voltage. forward voltage depends on the color of the led, and varies wildly
i f'ed up on the current stuff though, and this is why you want to use as many leds in series as possible. each series string will only draw 20mA regardless of the number of leds, so you want as many on them as possible and avoid just wiring a whole bunch of parallel leds with resistors.
so this is what i'd do.
two 4-led series wired as above, but with a ~50 ohm 1/4 watt resistor just to be sure you protect the leds if the battery goes above 9v which it probably will.
for the blinking led, use two of the red tinted ones in series, and without a resistor. it's not needed as the leds can take up to 5v a piece, and the 9v battery will never get to 10v. use these instead of the clear one because you can use 2 and the current draw will be much less(more than half as much as) than the single clear one.
so it will last quite long with this setup. assuming the two 4-led series strings draw max 30mA each, and the blinking one is 30mA max, that is at most 100mA being drawn from your battery. you need a minimum of 6v in the battery to keep these leds spitting out some kind of light. I would hazard a guess and say the 565mA on a 9v battery would last until around 6v, so you're looking at roughly 4.5-5 hours for this.
wire a switch in there, and parallel a couple more 9v batteries (not too much, battery internal resistance might start to mess with things i think) and you can make it last for days.
FV on the eight can be 1.7v - 2.2v. the one blinking led can take 10v directly, and is 70mA. the other blinking one is 3-5 forward voltage. forward voltage depends on the color of the led, and varies wildly
i f'ed up on the current stuff though, and this is why you want to use as many leds in series as possible. each series string will only draw 20mA regardless of the number of leds, so you want as many on them as possible and avoid just wiring a whole bunch of parallel leds with resistors.
so this is what i'd do.
two 4-led series wired as above, but with a ~50 ohm 1/4 watt resistor just to be sure you protect the leds if the battery goes above 9v which it probably will.
for the blinking led, use two of the red tinted ones in series, and without a resistor. it's not needed as the leds can take up to 5v a piece, and the 9v battery will never get to 10v. use these instead of the clear one because you can use 2 and the current draw will be much less(more than half as much as) than the single clear one.
so it will last quite long with this setup. assuming the two 4-led series strings draw max 30mA each, and the blinking one is 30mA max, that is at most 100mA being drawn from your battery. you need a minimum of 6v in the battery to keep these leds spitting out some kind of light. I would hazard a guess and say the 565mA on a 9v battery would last until around 6v, so you're looking at roughly 4.5-5 hours for this.
wire a switch in there, and parallel a couple more 9v batteries (not too much, battery internal resistance might start to mess with things i think) and you can make it last for days.
