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Topic: WS2812b led strip and arduino, should I give up? (Read 1 time) previous topic - next topic

sblantipodi

Jan 17, 2019, 09:46 pm Last Edit: Jan 17, 2019, 10:00 pm by sblantipodi
Hi guys,
I used for two months a 95 LED strup (60 led per meter cutted) WS2812B 5V on my ESP8266

This was my setup.



after some months I wasn't able to control the led anymore. I tried everything, cutting the first led, the second one, the third one. The led strip was dead, only some leds lighted up and every others shutdown.

I tried everything and the strips seemed dead so I bought another strip and connected only 10 leds to it just to give it a try. same things, the strip was dead.

So I decided to try a different approach with this schema


basically I used a logic converter to up my 3.3V digital pin to 5V. I also added a resitance of 470omh.

nothing, I can't control the strip. strip light up but leds are out of control, some leds off and some others with some strange color.

power supply seems to be in a good state and connection seems to work well.



should I give up?
what can it be?

CraigMurphy

Replace parts with known good ones. Find the bad part.

sblantipodi

Replace parts with known good ones. Find the bad part.
I replaced the ESP, I replaced leds, I replaced the logic level converter, I replaced the capacitor, the resistor,
the only part I haven't replaced it the power supply.

can it be the power supply?

sblantipodi

I tried changing the power supply. Still I can't drive the led.
LEDs lit up but I can't drive them.

Can it be a software problem?
Is it possible that the same sketch doesn't work anymore after some libraries update I have done in the Arduino IDE?

I really don't know what to think

PaulRB

#4
Jan 18, 2019, 08:10 am Last Edit: Jan 18, 2019, 08:15 am by PaulRB
You should have a resistor connected to the data line. I can only see that in your first picture. You should also have a large cap, e.g. 1000uF, across the power supply lines, close to the start of the strip.

Instead of your logic convertor module, you can try a 74hc14 chip. Power the chip with 5V. Each chip contains 6 inverter gates. You will need to use two gates, connected in series. As with any chip, put a 0.1uF cap across the 5V & ground pins, close to the chip.

sblantipodi

You should have a resistor connected to the data line. I can only see that in your first picture. You should also have a large cap, e.g. 1000uF, across the power supply lines, close to the start of the strip.

Instead of your logic convertor module, you can try a 74hc14 chip. Power the chip with 5V. Each chip contains 6 inverter gates. You will need to use two gates, connected in series. As with any chip, put a 0.1uF cap across the 5V & ground pins, close to the chip.
I tried with the resistor and the capacitor.
the problem is that now it doesn't work even with the simple schema that it is always worked.

can it be a software problem?
sketch is not changed but I updated libraries. can it be a problem of software that it compile ok but than does not work for some new libraries I installed?

PaulRB

Your first pic shows a Nano. This is a 5V Arduino. The others show esp-based Arduino which are 3.3V. This could be the reason.

sblantipodi

Your first pic shows a Nano. This is a 5V Arduino. The others show esp-based Arduino which are 3.3V. This could be the reason.
pictures shows different devices but I always used the ESP8266 with wemos d1 mini.

I finally finded the problem. My power supply, I don't know why, started to give 13V instead of 5V.
he burned my strips as soon as I attached them.

finally, I finded the reason. thank for the support guys!

sblantipodi

#8
Jan 18, 2019, 08:48 pm Last Edit: Jan 18, 2019, 08:49 pm by sblantipodi
just the last question.

is 220ohm enough if using an ESP8266 with a logic level converter that bump the GPIO from 3.3V to 5V?
can you explain me the reason why use a resistence for the GPIO and a capacitor for the power ?

Grumpy_Mike

The resistor stops reflections and protects the input, especially if the signal is applied with no power to the strip.
The capacitor stabilise the voltage and prevents damage to the power supply.

PaulRB

The capacitor I can explain. Even with thick wires, there is some resistance. This limits the current flow. That limits the speed that voltage can return to normal when the current suddenly changes, like when a bunch of pwm controlled LEDs switch on or off. When the voltage cannot return to normal quickly, this affects the data signal, indirectly, because the voltage of the data signal is always compared, by the chips on the strip,  to the supply voltage. If the data voltage cannot quickly return to normal, the data gets, or appears to be, corrupted. The capacitor near the start of the strip acts as a local reservoir of charge, so charge does not have to be transferred over the long wires, there is a local supply available. So the power to the strip remains more steady, and the data signal is less likely to appear corrupted.

sblantipodi

Thanks for the answer guys. I really appreciate your help

Another questions if possible.
Why they say that a 220ohm / 470 ohm resistance is ok?

Should I choose 220 or 470?
I choosed 220ohm for esp8266 + logic level converter from 3.3 to 5v, was I wrong?

Another question. I have 95 LEDs ws2812b with smd5050.

Should I power the strip on two side or one side is enough?

Thanks

Grumpy_Mike

#12
Jan 19, 2019, 01:35 am Last Edit: Jan 19, 2019, 01:37 am by Grumpy_Mike
Quote
Why they say that a 220ohm / 470 ohm resistance is ok?
It offers a good balance between protection and not cutting the drive voltage down too much. Mainly from imperial experiments.

Powering from both sides is always preferable if possible.

Quote
I choosed 220ohm for esp8266 + logic level converter from 3.3 to 5v, was I wrong?
You should always have the resistor the 5V side of the of the converter.

I am not convinced that those I2C converters are fast enough for Neopixel driving.

Paul__B

Mainly from imperial experiments.
While poor old Phil may have been driving Land Rovers until yesterday (and I strongly suspect will not be driving them any more), I would be distinctly surprised if any of the family knew what an Arduino or WS2812 was.

empirical

I am not convinced that those I2C converters are fast enough for Neopixel driving.
Sounds dodgy.  A 74HCT14, or even a 74HC14 would be far more appropriate with two gates in series.

Grumpy_Mike

#14
Jan 19, 2019, 09:34 am Last Edit: Jan 19, 2019, 09:35 am by Grumpy_Mike
Quote
empirical
Dyslexia rules KO.  :)

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