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Potentiometer
cholin:
Okay thanks alot, now here comes the problem, its not displayed in Ohms. It says like 1k pot, 2k pot, etc. Look at this page as an example:
http://futurlec.com/PotRot.shtml
Which one of THOSE should I buy then? They are in 1/2 watts, although I know nothin about pots so I cannot say if thats sufficient.
tetsujin:
--- Quote from: cholin on February 24, 2005, 04:19:11 pm ---I will have a resistor, heres a picture of what I want, this way I just want to know which potentiometer can output 5v MAX, 0v MIN when 5v is supplied.
--- End quote ---
Well, the potentiometer doesn't really output voltage at all.. it's a variable resistor. The LED turns off when there's no longer enough current flowing through it to produce an appreciable amount of light.
Most likely your series resistor will be 1/4 watt, so 1/2 watt rating on the pot should be fine.
I'm not really sure how much resistance you need to put in-line before your LED will be unable to operate. That's the main thing you want to match to the value of the potentiometer. You might be able to get the minimum operating current for the LED from its datasheet, if you have that. Otherwise, you might just need to experiment.
I'd start with a pot with maybe 4 times the resistance of your series resistor. That'd probably cut it down low enough. A higher rating on the pot will make the LED able to go dimmer, but it'll also mean more of the turning space will be in the "dim" range, so you won't have as much fine control over the brightness. (In other words, all your "on" range will be too close together.)
cholin:
Come to think of it, the LED doesnt have to go off at all, it just needs to have a fine brightness control. It does not need to go super dim, but maybe half of what it could be, so if it operates at 4 volts now with a 50 ohm resistor, I should but maybe a 100ohm pot so that it just fine tunes. I still need to know though, because it doesnt say "100 OHM POTENTIOMETER", it says "1k POTENTIOMETER" so I don't know the conversion.
tetsujin:
--- Quote from: cholin on February 24, 2005, 06:16:00 pm ---Come to think of it, the LED doesnt have to go off at all, it just needs to have a fine brightness control. It does not need to go super dim, but maybe half of what it could be, so if it operates at 4 volts now with a 50 ohm resistor, I should but maybe a 100ohm pot so that it just fine tunes. I still need to know though, because it doesnt say "100 OHM POTENTIOMETER", it says "1k POTENTIOMETER" so I don't know the conversion.
--- End quote ---
1K = 1000 ohms.
cholin:
So thats WAY to much then, whoa! Are you sure about that though, because anything lower than 1k is measured in R, such as 10r, 600r, 999r, then it goes 1k, 100k, etc.
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