LED won't shut off completely.

Using Arduino Programming Questions
1

so i followed this LED strip tutorial: Digital RGB LED Strip tutorial

basically I've followed the circuit with the TIP 122 transistor, and I'm trying to fade between 3 led strips. they all work, except one of the strips will not completely turn off. I'm not sure if anyone has some quick suggestions/tips why this might be happening.

the code has been tested and works fine with lower voltage LED's. I've adjusted the circuit to take into an account an external power supply instead of the Arduino power due to low amperage and not enough voltage.

help?

2

We need to know what you have done. That tutorial is about an addressable LED strip. You can't dim those with PWM.

3

I've been dimming them with PWM. and have tested a digital write to it. same results.

4

You can dim them, simply give it a lower voltage - but that doesn't mean it is correct.

5

The link you posted doesn't mention a TIP122 transistor. Maybe you posted the wrong link?

6

the circuit just asks for power transistors. tip122 would work just as fine. i am setting the voltage to 0, using an analog write function, i.e.

analogWrite(led, 0);

7

is any of this relevant?

We haven't seen your code (hint) so we can't tell.

8

danieljay:
the circuit just asks for power transistors. tip122 would work just as fine. i am setting the voltage to 0, using an analog write function, i.e.

analogWrite(led, 0);

I still think you have linked to the wrong page, I can find no reference to power transistors on that one.

9

danieljay:
so i followed this LED strip tutorial: Digital RGB LED Strip tutorial

basically I've followed the circuit with the TIP 122 transistor, and I'm trying to fade between 3 led strips. they all work, except one of the strips will not completely turn off. I'm not sure if anyone has some quick suggestions/tips why this might be happening.

the code has been tested and works fine with lower voltage LED's. I've adjusted the circuit to take into an account an external power supply instead of the Arduino power due to low amperage and not enough voltage.

help?

Might be leakage current in the transistor - does that strip still glow a bit if the TIP122 base is connected to ground?