I'm trying to use an RGB LED to make a dimmable lamp for myself, but I'm pretty confused. The LED I'm using is a Z-Power P1 (spec document here). I'm putting a pot in series with each LED and resistor, so there are 3 sets of pot--LED--resistor in parallel. I've read plenty of sites in an attempt to get my head around this, but I'm confused for several reasons.
First, this LED package shares a single anode between each LED element in the package. All of the sites I've read show that the resistor that goes in series with each LED should go on the anode side of each LED, which I obviously can't do here. If I put the resistor on the cathode, won't that drop the voltage to my LED? In order to get ~.35A to each LED branch of my circuit, I think I need about 13 Ohms of resistance, which would drop all of my voltage before the LED.
Second, I did a project to make a mood lamp (link), which is why I have one of these Z-Power LEDs lying around. I'm looking at the resistor values that guy chose in his project, and they don't make sense to me. With his 3 resistors, the total resistance of his circuit should be something like 1/((1/5)+(1/10)+(1/15)) = 2.7 ohms. With a 5 volt power supply, he should be drawing 1.85 amps, but he only calls for a 1 amp supply. Does his circuit only work because the power supply is hitting its limit? I understand circuit math better now than I did when I did the project, so I'm confused about why something that I know works doesn't seem to meet up with my understanding of the math.
Also, I have a general LED question. LEDs are current controlled devices, so what happens if there's not enough voltage at a given current? Does the device just get dimmer, or does the LED not get enough voltage to conduct, or what? I'm wondering this because it's not entirely clear to me how a potentiometer and an LED interact, since one controls resistance/voltage, and the other is controlled by current.
I've read over this post several times, and I keep halfway convincing myself that I know an answer to a given point, but I think I'd rather have some real advice instead of smoking a $20 LED. Any help would be appreciated!
First, this LED package shares a single anode between each LED element in the package. All of the sites I've read show that the resistor that goes in series with each LED should go on the anode side of each LED, which I obviously can't do here. If I put the resistor on the cathode, won't that drop the voltage to my LED? In order to get ~.35A to each LED branch of my circuit, I think I need about 13 Ohms of resistance, which would drop all of my voltage before the LED.
Second, I did a project to make a mood lamp (link), which is why I have one of these Z-Power LEDs lying around. I'm looking at the resistor values that guy chose in his project, and they don't make sense to me. With his 3 resistors, the total resistance of his circuit should be something like 1/((1/5)+(1/10)+(1/15)) = 2.7 ohms. With a 5 volt power supply, he should be drawing 1.85 amps, but he only calls for a 1 amp supply. Does his circuit only work because the power supply is hitting its limit? I understand circuit math better now than I did when I did the project, so I'm confused about why something that I know works doesn't seem to meet up with my understanding of the math.
Also, I have a general LED question. LEDs are current controlled devices, so what happens if there's not enough voltage at a given current? Does the device just get dimmer, or does the LED not get enough voltage to conduct, or what? I'm wondering this because it's not entirely clear to me how a potentiometer and an LED interact, since one controls resistance/voltage, and the other is controlled by current.
I've read over this post several times, and I keep halfway convincing myself that I know an answer to a given point, but I think I'd rather have some real advice instead of smoking a $20 LED. Any help would be appreciated!