Help Cant figure out why LEDs dont work

Hey Guys,

I have been tearing my hair out and cant figure out why LEDs stopped working. Maybe you can give me some ideas on how to solve/test the issue with either set up or WLED.

Below I am going to abbreviate Roof Dormer as - “RD”.

Background: I am using WS8212b. Everything worked really well prior to my attempt to connect RD 4 (*including RD 3!) on the schematic below. I may have crossed the wires red/black while testing downstream of RD3 and upstream of RD4. I could not get Roof Dormer 4 to light up.

Now RD 3 does not light up at all anymore. I am pretty sure that the wires are well connected at the inlet.

Question 1: Is it possible to burn out the entire chain of LEDs ~ 122 of them (RD3)? I tried connecting DigiUno and power supply just for RD3 and it’s not lighting up.

Question 2: Do WS8212b’s have some sort of stored memory where they were turned off before and are still turned off until another signal comes in telling it otherwise?

Everything up to RD3 works perfectly now.

When I connect a brand new reel of WS8212bs at the inlet of RD 3 and take RD 3 off I only see one pixel light up blinking different colors.

Is there a way to test “Signal Wire” to see if the signal is not getting through to the RD3 connection point? The voltage I am testing was at about 3V but when I included injection at that connection it went up to about 4 volts.

I do have an amp limiter set in WLED app and the power supply is making the noise of a fan running so its working hard.

I also need to understand why LEDs don’t work for RD 4 at all.

Can you give me some ideas on how I find a solution to my problem? One note which is important one. It is very hard for me to get to the LEDs at RD3 and RD4 they are about 40 foot up in the air.

Also can you look at the schematic and tell me if the second wire with 5V can be wired the way I have it shown?

Thank you!

Question 1: Is it possible to burn out the entire chain of LEDs ~ 122 of them (RD3)?

Not usually. The first few can die gumming up the rest.

Question 2: Do WS8212b’s have some sort of stored memory where they were turned off before and are still turned off until another signal comes in telling it otherwise?


Other items of note:

Power supply voltages -
3V is too low and 4V is pretty marginal, you need to look at more power injection in your setup.
Make sure your adding both V+ and ground at injection points.

Data distances -
The distance the data signal can go between strips and/or LED’s is limited.
My rule of thumb is no more than 2m between a data source and it’s “receiver”.
Lots of discussions on ways around that, my ultimate is use a TxRx differential pair.

Thank you @divsys ! I have about 5-7 meters between RD1 and RD2 and about 5-7 meters between Rd2 and RD3.

What would my solution be? saw this video and ordered two of these 3-wire data boosters. But i don’t know where to place them - right after the DigiUno or can I place one of these where I am having issues after about 800 LEDs downstream?

Just today, i took off plus and minus from the 3-wire cable (which includes data cable). I left just the data cable, and used a brand new power supply . I now can get the strip to light up but lights are all wrong colors. :frowning:

I don’t know what my solution may be besides using another DigiUno and a new power supply at that point.

One more question for you, is it possible that DigiUno went bad. Somehow DigiUno is confused and saying the LED strip to do these things?

Thanks again.

For me, I switch to TxRx differential data at those distances.
The 3 wire booster you liked, may work for you but IMHO it’s a kludge to try and get 5V data over distances it was never meant to travel.

When you took of the Power, Data, and Gnd then hooked up only the Data you’re missing a ground (0V) reference. Your LED strip doesn’t “know” where 0V is any more. You have to connect both Data and Gnd.

The DigiUno might be bad, or a bad flash version. Try testing a small section on the bench to prove it will control anything.

The TxRx pair I referenced to solve the data issue are devices like: Basic RS485 or : RS485 protection and flow control

The first is a basic device pre-configured as a Transmitter (Tx) that sends data over two wires A+, B- (plus Gnd) to a Receiver (Rx). You make a Tx into a Rx by tying the the DE & RE lines together and to GND.

The 2nd device is a little more sophisticated as it adds surge protection to the A+ B- lines. It also defaults to Rx and automagically detects when you try and transmit data to a module to turn it into a Tx so you don’t need to configure which module is TX and Rx. You may need to jumper the onboard termination resistors (typically 120 ohm) depending on the board.

Typically put the Tx near the data source (DigiUno or the end of a string) and the Rx near the start of the next string in the chain. Data from the source goes to DI (Data In) and drives the string from DO (Data Out). You need to power Tx & Rx from +5V, although they need very little current ( < 0.1A)

You don’t need level shifters at all as they can handle a 3.3V input properly and output 5V data.

There’s tons of these available on Aliexpress if you’re willing to wait.

@divsys Thank you again!, I want to make sure I understood what you said. Are you saying that Data Cable also needs negative (Ground) that comes out of LED strip to work correctly?

So do I need data cable, ground that comes out of the previous LED strip and a 5V from power supply which is a plus and a minus?

When I tested on a small strip with my DigiUno works fine for 150 LEDs I will try to connect more to see if that would create problems. Also thank you for mentioning TxRx. I’ll have to research it more. I have never heard about it before now.

Yes Data needs a ground reference. People often ignore that as the power supply ground (the minus in your plus minus from 5V) is usually common to both the MCU (Digi Uno in your case) and the strip. But it can make a difference if you have a long run with major current draw. The rule of thumb is “connect all the grounds together” which is generally correct, but not always sufficient.

Personally I prefer to think of these setups as a Power section and a Data section.
Power needs to worry about total amps, voltage drops, heating, wire gauge, etc.
Data needs to worry about clean signal, there’s really no current to speak of (a few milliamps at worst).

IMHO, TxRx is the simplest solution to many of the longer run flicker, “weird” display issues. It just takes a little different mindset to understand how/why it works so well.