I made two LED controllers using an ESP. On the PCB I'm using three 2N2222 transistors + resistor (1k Ohm) at the base to control the 12V circuit powering the LED strips by applying 3.3V from the ESP.
Schematic (Q1, Q2 and Q3 have been replaced by the transistors):
Now I've got a problem: On one of the two controllers the Q2 transistor keeps blowing (Q2 is RED, not GREEN, as I accidentally mixed something up). It seems to be the LED strip, because I put it in place of the other controller and now it's working fine.
Could the problem be that the LED strip is too long? Or is there something faulty and I need to replace the whole strip?
If more info is needed, I'll gladly provide it.
Edit: I still have the original controller, which uses an IR remote. If there's anything I need to measure while the strip is on, I can do that too.
The resistor soldered to the base of the transistor works, I just checked that. The red LEDs start flickering, and at some point the transistor blows
Best Answer
Most 2n2222 transistors have a max Ic collector current of 800mA. If each LED (only one color) drew 20mA and you had 60 (usually what a 2m strip has) of them that would be 1.2A which means you'll burn the transistor out. If your using this with a controller, then it could source amps of current which will also kill the transistor.
The other problem with modifying the schematic is NPN's are lossy and generate loads of heat under high currents. It would be better if you stuck with the original irlb8721's as a low side switch. They must be used as a low side switch and not high side.