Hello, I recently bought and wired up a few segments of 2812 leds (60 pixels/m) using one NodeMCU per section as undercabinet lights. The pixel segments counts were 64, 16 and 48. Based on the count, I attempted to only use a 2A phone charger style usb to power the Nodemcu and the lights. I’ve never done anything with any Arduinos before and figured I’d jump in with both feet. It took some time for me to understand how to flash the boards but I got all the sections up and running smoothly.
Now for my questions:
Should I be using a level shifter for runs this short? I see that I can do it, but is this going to cause issues later? I have one more section to do and don’t want to install everything again is I don’t have to.
My section of 64 pixels has quit responding about a week ago. I can’t access the NodeMCU through the app and no open AP is being broadcast. Usually, the first pixel is green but it’s sometimes orange. Nothing else is lit up. Does this mean something? I’ve found a few posts talking about similar issues but my interpretation was that the other issues were on startup not after running well for a few weeks.
Thanks for any help that can be provided.
If more info is needed, please let me know.
Edit: I forgot to add, I’m driving all three segments off the 3v3 pin. I had some flickering on the 5v pin and this dimmed the output slightly on full white but removed the flicker.
Hi and welcome to the forum ,
Did you see the diagram in the link before ?
I did see, and had to read the wiki several times during my initial setups. I originally had the power tied to the 5v pin on the NodeMCU, but one strip had a minor flicker so I attempted to run it off the 3v3 and everything appeared to work well.
I had read in several places that the level shifter was an optional part. I understand their use for long runs, I think. Everything I have from the outlet to the first pixel is within 12 inches.
LED strips need a sufficient power supply to work properly, a 5V supply is essential - things may work at 3.3V but you’re not guaranteed anything. Not to mention the 3.3V converter on the NodeMCU is not designed to supply a large number of off board devices.
As an initial guess, I would say your flickering issues at 5V had to do with trying to get enough power through a USB port. USB’s fine for driving the MCU, but not for the led strips. You need to supply the strips directly with proper power. Either splice a separate power cable for them or add a second supply driving their power pins directly. I would power from the middle of your strip to minimize voltage drop issues.
If the MCU to 1st pixel run is only 12 inches, you may get by without a shifter or worse case, you could use a sacrificial pixel.
You didn’t mention what version of WLED you’re running?
I’m currently running 0.13.0 beta 6 on all sections. It’s been great before the one section failed. I’m 99.9999% sure it’s not the software that’s causing my issue.
I figured my issue was something I did. Even though I got it to work it shouldn’t be done like I set it up. Thanks for all the help.
I’ll look into a level shifter and power supply.
Anyone have a suggestion for a small and reliable power supply? Id like to mount/ hide everything in the trim below the cabinets if possible.
Start with what your maximum worst case power requirements will be.
I’d guess at ~130 LED’s your max power is around 30W or 6A.
If you’re trying to hide the PSU(s) you may be better off with two smaller 3A units feeding each side.
Lot’s of options at those power levels. If you go for one larger supply, you could put it farther away and run an injection point to the center of your strip(s).
I may have used the wrong words when describing my setup. I have three seperate sections with 68, 18 and 44 pixels respectively. My cabinets are in an odd configuration, but they do have 110v outlets in each area.
That is the main reason I tested out using smaller 2A phone chargers as the power supplies.
If you have 3 x 2A chargers with good wiring connections capable of delivering 2A each, that should work fine.
Thank you for the help. I think I’m just going to start over and not be lazy this time. I just need to model and print some new enclosures. I can reuse everything I already bought.
I had a question, but read the level shifter info wrong. I had it confused with something else.
Good luck (you won’t need it)
Let us know how it works out.
After recieving level shifters and 3A power supplies, i realized i forgot he wiring diagrams recommend a cap and resistor. Are these sizes still the best? I’ve read some changes in what people are liking through experience. I’ve always been bad at building circuits so I need a suggestion / confirmation.
For the cap: 25v 1000uF. I think I understand the sizing on caps, is this good?
For the resistor: 62 Ohm, but what wattage? I never understand resistors.
Thanks for the help!
The strip capacitors (if needed) are to supply “surge” power during maximum brightness effects. 1000uF or bigger and voltage at least 20% more than the strip voltage, so 1000uf @ 25V is fine. The other place a capacitor is often needed is to bypass the switching noise on the level shifter. This will be placed right near the shifter across its power pins. It’s a small ceramic capacitor, the value is typically 100nF and 10V.
Resistors (if needed) are not about carrying power in this application. They are used as “impedance matching” components so any power value (1/4W) will be fine.
If you are using the chip-form of the AHCT level shifter, you need a 0.1uF capacitor across Vcc and GND of the chip, right at the chip.
I’m not really sure the style of level shifter I ordered. I’ve had success with this company on other projects and used their shifters.
HiLetgo 10pcs 4 Channels IIC I2C Logic Level Converter Bi-Directional 3.3V-5V Shifter Module for Arduino https://www.amazon.com/dp/B07F7W91LC/ref=cm_sw_r_apan_glt_i_FYS5ZTRP9ZRNTZMD5YZZ?_encoding=UTF8&psc=1
I2C is too slow. See knowledge base for suggestions.
Well, nuts. I’ve already soldered up a few of them.
I don’t doubt what you’re saying, but what is the issue with it being slower than recommended? I would guess that these will 95% of the time be solid white and only something else for special holidays.
I looked at the reccomended shifters and they all appeared to be more for printed boards than a prototype board setup. Maybe I read it wrong. They just looked overkill for what I thought I needed.
The issue with a slow shifter is that it can corrupt the data stream by changing the (critical) timing of the pulses. The problem is you won’t know you have an issue until it suddenly (or worse, sporadically) appears Depending on the distance(s) you have to send data, you might get away without out one at all or sub in a sacrificial pixel.
I often get away with nothing at all attached directly to an ESP32 board. I have soldered a SOIC style 74AHCTxx chip onto a SOIC->DIP adapter board so you end up with a small flat PCB that’s no larger than a 14 pin DIP. A little soldering and it will fit very nicely in most setups.