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Topic: LED won't shut off completely. (Read 1 time) previous topic - next topic

so i followed this LED strip tutorial: http://www.ladyada.net/products/digitalrgbledstrip/index.html

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?

Grumpy_Mike

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

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

Jassper

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

dc42

The link you posted doesn't mention a TIP122 transistor. Maybe you posted the wrong link?
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

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);

AWOL

is any of this relevant?

We haven't seen your code (hint) so we can't tell.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

dc42


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.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

MarkT


so i followed this LED strip tutorial: http://www.ladyada.net/products/digitalrgbledstrip/index.html

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?
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