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Topic: TLC5940 HELP! (Read 480 times) previous topic - next topic

ammygo

#15
Jan 23, 2019, 07:26 pm Last Edit: Jan 23, 2019, 07:31 pm by ammygo
sorry I use IRF540 not IRF640, my mistake. And it fully turn off, I dont know about fully turn on because I cant see small difference of bright led.

I use schematic like GeronimoDK made, but dont use any resistor between 12V + and LED strip +.

When I switch IRF540 to IRF610 LED strip led dont fully turn off.

I can film it if you want.

And then I programming TLC to turn on LED strip I have to write:
Code: [Select]
Tlc.set(7, 0);
so if I understand wright then I power on TLC output it close IRF540, if I do nothing with TLC output IRF540 is open, wright?

Grumpy_Mike

Quote
And it fully turn off,
No are you not reading what I say?

The transistor fully turning off is not the problem. The transistor not turning on "fast enough" is masking the problem you have due to faulty design of the circuit.


ammygo

#17
Jan 23, 2019, 07:44 pm Last Edit: Jan 23, 2019, 07:46 pm by ammygo
No are you not reading what I say?

The transistor fully turning off is not the problem. The transistor not turning on "fast enough" is masking the problem you have due to faulty design of the circuit.

so how should I build everything to do it right? can you draw I scheme?
I run fade up and down code and it looks "fast enough" for me, no lag or blinking. But if circuit is bad I want to know how to do it right.

wvmarle

What is "very slow" for a MOSFET or an LED is still orders of magnitude faster than your eyes can see.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

ammygo

fix me if I'm wrong:
TLC is faster then transistor can work. right?

Grumpy_Mike

Quote
I run fade up and down code and it looks "fast enough" for me, no lag or blinking. But if circuit is bad I want to know how to do it right.
It is the signal that is slow not anything you do with it. What you might see is that the numbers you put in do not change the brightness as you would expect. You will also notice that the FETs get hotter than they should do.

The way to do it correctly is to invert the signal feeding into the FET, or to have the circuit you have but use a P-channel FET in the +12 line with the + of the strip connected to the FET's source and the -ve of the strip to the ground.

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