RGB Potentiometer help!

Hey guys and girls, I've got a question! I've got 3 voltage regulators set up in parallel, wired to output 3.27V @ an amperage that I don't know (for some reason I can't get a reading on my e-meter) Anyway, The outputs from those 3 regulators are going to 3 pots, which in turn go to a set of 3 LEDs, 9 in total (3R 3G and 3B). My problem is that those pots have a max resistance of 2k ohms, and that the LEDs aren't shutting off when the resistance is maxed out. Can you guys find a way to make the LEDs shut off, yet still go on at full blast when the Pots are open? Thanks, -Josh

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Dan's Schem.jpg
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lacrimax8 years ago
For a dimming a led you need work with PWM pulse width modulation, non for voltage variation, in a few days a i gonna make an instructable and get you a pcb for a dimming control using an le555, now i need to find a mosfet that works fine, other thing that you need yo think if you gonna make you one is you gona need a npn transistor for sitching the mosfet that work about 190 mhz for fast and good switching dimming. the led is not a inductance light , the led works with ions . don´t waste your money, varing the voltage you can the led in 10 percent 30 percent and 100 percent , read about pwm. or wait my pcb is very cheap.
NachoMahma9 years ago
. Not sure I understand, but try using a "larger" pot. I'll guess that 47K would be easy to find and work well enough to tell if that's the problem. If 47K is too sensitive, try something a little smaller until it feels right.
T3h_Muffinator (author)  NachoMahma9 years ago
The thing is, I want the ratio between the resistance and the power output of the LED to be almost direct, not exponential. I'm going to draw up a schematic, but even with the 2k pot, the LED just suddenly clamps within the last 10 degrees of the pot's rotation. This isn't what I want. I think I might have the wrong set-up. I think my pots are in the wrong place, according to Dan's schematics for his RGB high-powered lamp, that is.
. If you are using a linear taper pot, get a log (audio) taper. And vice versa.
T3h_Muffinator (author)  NachoMahma9 years ago
What are those?
. Maybe this will explain a little better. Assume a 100 ohm pot with a dial calibrated 0-100. . With a linear pot, 25% on the dial will give 25 ohms, 50/50, 75/75, etc. . . Don't have a real good explanation for logrithmic. If the pot gives 10 ohms at 10% on the dial, it will give 100 ohms at 20% and 1000 ohms at 30%. That may not be exactly right, but it gives you the idea. . Ever notice how on a audio frequency response chart the low frequencies are spread out and the high frequencies are jammed together? Same thing.
T3h_Muffinator (author)  NachoMahma9 years ago
ahhh, got it now. The linear pots have a direct relationship, they follow a "linear curve", whereas the taper pots follow a logarithmic curve.
. Doh! I misjudged your level of knowledge/experience. That's it exactly.
T3h_Muffinator (author)  NachoMahma9 years ago
That's alright! Thanks for all the help!
LasVegas9 years ago
I have a circuit that will allow adjusting the brightness of LEDs by adjusting the current rather than the voltage. While it's quite a bit more complex, it allows driving many more LEDs and a more linear brightness change. If you'd like, I'll share the circuit with you in private.
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