OK, folks, this is really on topic because I’m using my lathe to make the thing that needs this. But when it comes to electronics, I’m totally helpless. Cams, gears, levers; I can see those. Electrons are invisible and just not part of my brain’s capabilities.
So here’s the situation: I need an indicator light made from a blue LED and run off batteries. I need the light to last for about 40 hours on a battery or set of batteries. Because of the size of the project, battery size is limited to two AA or one 9V, (or smaller-- button cells would work if I can get the hours out of them). The blue LEDs seem to require about 3.5 to 4 volts.
Question 1: Intensity of the light is not a big issue; this is for dusk and night use so the light does not need to be bright enough to be seen in bright daylight. Can I just run a blue LED off two AA alkaline batteries without a resistor? (I know I’d need one with a 9v. battery.)
Question 2: When I look up AA and 9v. batteries on Wikipedia, I get 3000 mAh for a single AA alkaline, yet only 565 for a 9v. Is this right?
Question 3: If the 3000 mAh for an alkaline AA is correct, am I right in thinking that two of them gives me 6000 mAh? And if the LED draws 20 mAh, I’d have 300 hours worth of light?
Question 4: And if those numbers are wrong, how many hours would a 20 mAh LED run on two AA batteries (first choice) vs. a 9V battery (second choice)?
Bonus question: I have a little keychain LED light powered by four LR 41 batteries that could be used for the project. At 20 mAh for each battery, does this give me 80 mAh and therefore four hours of light?
THANKS for the help, guys!
So here’s the situation: I need an indicator light made from a blue LED and run off batteries. I need the light to last for about 40 hours on a battery or set of batteries. Because of the size of the project, battery size is limited to two AA or one 9V, (or smaller-- button cells would work if I can get the hours out of them). The blue LEDs seem to require about 3.5 to 4 volts.
Question 1: Intensity of the light is not a big issue; this is for dusk and night use so the light does not need to be bright enough to be seen in bright daylight. Can I just run a blue LED off two AA alkaline batteries without a resistor? (I know I’d need one with a 9v. battery.)
Question 2: When I look up AA and 9v. batteries on Wikipedia, I get 3000 mAh for a single AA alkaline, yet only 565 for a 9v. Is this right?
Question 3: If the 3000 mAh for an alkaline AA is correct, am I right in thinking that two of them gives me 6000 mAh? And if the LED draws 20 mAh, I’d have 300 hours worth of light?
Question 4: And if those numbers are wrong, how many hours would a 20 mAh LED run on two AA batteries (first choice) vs. a 9V battery (second choice)?
Bonus question: I have a little keychain LED light powered by four LR 41 batteries that could be used for the project. At 20 mAh for each battery, does this give me 80 mAh and therefore four hours of light?
THANKS for the help, guys!
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