As the title suggests i have somewhat of a noob question. I require the use of a series of LED's to fade out as they turn off. I do not want to use any PWM because all available PWM channels of my Uc are in use doing something else. So my alternative is to just use a transistor or mosfet to turn the circuit on and then have the current drain through a capacitor and resistor in series with one another to ground.
The question is how would i calculate the wattage of the resistor that is in series with the capacitor. The reason i can't wrap my head around this is because not all of the current is actually going through the capacitor / resistor combo. Some of that current is still going to be going through the series of LED's other wise it wouldn't fade. Is there a way to know how much current is going through each?
I have attached an image for the sake of clarity. The cap would be 68uf the resistor in line with that would be 1.5kΩ, the current limiting resistor for the LED's would be 2.5Ω the LED's draw about 750ma each. The supply voltage is 12V. This causes the current limiting resistor to be a very high wattage. Lets say about 10W. Just wondering if there is a formula to calculate the wattage of the resistor in series with the cap then. Thanks for any help you can give.
The question is how would i calculate the wattage of the resistor that is in series with the capacitor. The reason i can't wrap my head around this is because not all of the current is actually going through the capacitor / resistor combo. Some of that current is still going to be going through the series of LED's other wise it wouldn't fade. Is there a way to know how much current is going through each?
I have attached an image for the sake of clarity. The cap would be 68uf the resistor in line with that would be 1.5kΩ, the current limiting resistor for the LED's would be 2.5Ω the LED's draw about 750ma each. The supply voltage is 12V. This causes the current limiting resistor to be a very high wattage. Lets say about 10W. Just wondering if there is a formula to calculate the wattage of the resistor in series with the cap then. Thanks for any help you can give.