Last week I through together an RGB fader for 12 volts, using 3 LEDs in series per color channel. Anyway, had a few problems, and had to cut a couple traces, solder some jumpers...
A ATtiny13 does the fading work, and used the same set up many times for single LEDs. But trying to step it up to a bigger and brighter is turning out a little more complicated then expected. I'm using a 7805 regulator, already smoked the 100 mA version, so bumped it to the 1 amp, which still got uncomfortably hot, so put a heatsink on it.
I origionally used a 2n3904s with a 10k base resistors for each color, but it would only light 2 out of 3 of the blue and green LEDs. After messing around with the LEDs to make sure the LEDs were fine (smoked a green in the process), thought the 10k was too high, so shorted the one for blue. Got all three to light, and bright like I wanted. Knowing its abusing the transistor, I replaced the 10k's with 1 ohm (have a bunch).
It works, but it's not right, and probably not safe, or likely to live like this for long. The 7805 still is getting hot, the AVR is getting warm (never happened before). Before dumping this PCB and starting over, what would be the proper base resistor between the AVR and 2n3904? Guessing this is where the heat problem is coming from. If not, then it's a bad board, and better to just start from scratch.
A ATtiny13 does the fading work, and used the same set up many times for single LEDs. But trying to step it up to a bigger and brighter is turning out a little more complicated then expected. I'm using a 7805 regulator, already smoked the 100 mA version, so bumped it to the 1 amp, which still got uncomfortably hot, so put a heatsink on it.
I origionally used a 2n3904s with a 10k base resistors for each color, but it would only light 2 out of 3 of the blue and green LEDs. After messing around with the LEDs to make sure the LEDs were fine (smoked a green in the process), thought the 10k was too high, so shorted the one for blue. Got all three to light, and bright like I wanted. Knowing its abusing the transistor, I replaced the 10k's with 1 ohm (have a bunch).
It works, but it's not right, and probably not safe, or likely to live like this for long. The 7805 still is getting hot, the AVR is getting warm (never happened before). Before dumping this PCB and starting over, what would be the proper base resistor between the AVR and 2n3904? Guessing this is where the heat problem is coming from. If not, then it's a bad board, and better to just start from scratch.