So I'm powering a few LED strips and using the Arduino to control them. I have followed the instructions on Usage | RGB LED Strips | Adafruit Learning System and am wiring them up with TIP120 transistors.
The problem is that no matter what I do, the blue LED is always on! Even when I turn off the arduino, the blue stays lit. Its not the strip (I tested that by switching it out), and it's not the Arduino, and I just replaced the TIP120 and that didn't do anything either. Any ideas? I've quadruple checked my wiring and it looks like red, green, and blue are all wired the exact same but for some reason that pesky blue led wont turn off.
If you swap (for example) the connections to the red and green LEDs, is it the green LEDs which now stay on permanently? If so, the problem is in your circuit / wiring, it would seem.
Please post a schematic diagram of your circuit (you can hand draw it and post a photo). And post some photos of your breadboard / circuit.
Ok so here is my circuit. Things to note: I am doing this on strip board. I am wiring two separate LED strip circuits running off of the Arduino onto the stripboard, so the red X's are where I broke the tracks. The emitters of all the transistors is the common ground, so I didn't break that strip. Sorry if this is kinda confusing with wires being everywhere. Every other color and everything works except the blue which I have notated. And yes if i swap the blue led for the red led, the red one stays lit permanently . I have replaced the transistor twice and the resistor once... its gotta be a wiring issue, but I have gone over this circuit so many times now and I see nothing wrong...
thank you so muchh for any helpp. i can take more pictures too, and explain what is going on if it is confusing.
I am going directly off of this diagram from the adafruit RGB strip tutorial:
You have shown two red Xs for each colour: one on the base and the other on the collector. But you have not shown a red X on the track above the base, on the other side of the base resistor. Could this be connecting to something that turns on the transistor?
Also, have you checked the back of the board for a solder bridge between collector and ground? or maybe a little piece of the copper where you have cut the tracks?
yah oops i forgot to add the other red x for the cut track for the data signal coming in, buut it turns out there was some kind of solder bridge between points on the back of the stripboard. just a lil exacto cleaning on the parts between the strips and it works!