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Topic: WS2812b led strip , should I connect 5V before than the digital pin? (Read 668 times) previous topic - next topic

Grumpy_Mike

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I connected a simple led on my ESP8266 d1 mini lite and it works so the output is ok.
No it is not. Are you actually paying attention?
We are trying to educate you not reinforce a slipshod approach to electronics.
I advise you read the last sentence of reply #12 again, or maybe for the first time.

sblantipodi

Never connect pins with power on.  Make ALL connections before applying power.
You can connect pins in any order while power is off, it makes no difference.
who is right?
mike says to give 5V before powering arduino, you say the opposite. a bit confused.

sblantipodi

but what controller should I use to safely control the LEDs?
I have the esp8266 d1 mini controller and it works awesome with wifi and mqtt,
what else can I use?

sblantipodi

No, testing a pin as an input is not going to tell you if it functions as an output. Just put an LED and resistor on the output.

By not fitting a resistor you are inviting problems, and just because you couldn't find one to drive a display is no excuse.

However now I know you are using a 3V3 processor the problem is more clear. The output signal is not enough to drive a strip reliably, yes it might work for a time as you found, but it is under the guaranteed to work voltage. You need a buffer to boost your signal then you can fit a 240 to 500R resistor for protection.
what is a buffer to boost signal? how can I create it?
will this buffer be fast? I need to use leds for monitor ambilight so they should be fast.

Grumpy_Mike

who is right?
mike says to give 5V before powering arduino, you say the opposite. a bit confused.
The two posts are not disagreeing with each other.

Read what boolrules says:-
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Never connect pins with power on.  Make ALL connections before applying power.
You can connect pins in any order while power is off, it makes no difference.
He is saying do not wire up the circuit with the power on, and I would 100% agree with that. You asked me what order should you apply the two power supplies, the Arduino and the 5V power for the LEDs. There is no disagreement that the 5V should be applied before powering up the Arduino. This is because if you power up the Arduino first the data signal will attempt to parasitically power the LED strip. Which the series resistor will protect against to a certain degree but it is best for this not to happen in the first place.

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what is a buffer to boost signal?
A circuit that converts the 3V3 volt signal to a 5V one.
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how can I create it?
Lots of ways, I use two buffers out of the six in a hex inverter like the 74HCT14 or similar. Like this one for the Raspberry, you can use exactly the same thing for your Arduino.



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I need to use leds for monitor ambilight so they should be fast.
No your application is irrelevant, the buffer needs to be fast enough to pass the data stream to the LEDs which is logic levels at 800KHz. This will not affect the speed of refresh of the LEDs, there is no way to affect this speed either faster or slower.

sblantipodi

mike is this something that can help me?

https://www.amazon.it/ihaospace-Channel-Converter-bi-directional-Arduino/dp/B06Y5KKMLL/ref=sr_1_2?ie=UTF8&qid=1547414692&sr=8-2&keywords=3.3V+to+5V+arduino

Grumpy_Mike

mike is this something that can help me?
No.
You do not need a bi-directional buffer.

sblantipodi

mike is this something that can help me?
No.
You do not need a bi-directional buffer.
can you help me buying a component that can help me?
why a bidirectional buffer will not help me?

a bidirectional buffer can be used in the direction I need, am I wrong?

from 3.3V to 5V? right? please help.

Grumpy_Mike

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a bidirectional buffer can be used in the direction I need, am I wrong?
Yes it can. However, what I don't know is if that buffer design is fast enough so I do not recommend it. It is designed for I2C signals which are a lot slower.

I recommend using a hex buffer chip like I showed you. I know that works, I have used it many times.

sblantipodi

Yes it can. However, what I don't know is if that buffer design is fast enough so I do not recommend it. It is designed for I2C signals which are a lot slower.

I recommend using a hex buffer chip like I showed you. I know that works, I have used it many times.
Thanks for the precious suggestion but I can't find it on Amazon or probably I'm not able to find it.
Can you give me some tips on name and what to find?
Thanks



sblantipodi


I bought both the logic level converter and the 74HCT14 but the logic level converter will arrive before than the
74HCT14  so I would like to try it first.

is this a good circuit example for my ESP8266?

Grumpy_Mike

Move the large capacitor as close to the LED strip as you can. Otherwise I can't see any issues.

sblantipodi

Move the large capacitor as close to the LED strip as you can. Otherwise I can't see any issues.
thanks my friend

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