Cat5 was installed for signal. What now?

Hardware
#1

My kitchen remodel includes new above and below cabinet LEDs. Following the advice of my friend who is a rocket scientist, and who happens to be an highly acclaimed EE, I installed cat5e cable for data signal and 18/2 for power. I’m now reading that cat5 is bad practice, even though my tests seem to be working, independently. I have questions :slight_smile:

Layout

4 cabinets, each with an upper and lower set of LED strips.

The “control center” is located approximately in the center, above the cabinet.

Setup

Power: 150W/30A power supply with 1 set of terminals going to controller and 63” set of LEDs, and the other terminal to three cabinets (3 runs, each with a pigtail to the lower LED bar); in-wall 18ga LED wire.

Signal: Eight (8) home-run cat5e lines - one to each LED strip.

CPU: ESP32 with a 8-channel logic level shifter

LEDs:

  • SK6812
  • 440 total LED’s on 8 strips, using ESP32 with 8 data signals
  • 7.32meters @ 18W/m = 132W + 20% = 158W

Status

I’ve tested the farthest runs, on both sides, and had 3 of the runs hooked up simultaneously to a ESP3266 (I’m switching to ESP32 to drive the whole setup).

One or two strips had a 330ohm resistor, the other did not. Two used GPIO output at ~3.3v over a single thread of Cat5 and I boosted the other with a logic level shifter to slightly over 5v.

With that, all three strips performed well.

Questions:

  1. Given that the cat5 is already installed, I can use it (preferred), or if not, place a small controller at each location and run 8 WLED instances. Is the concern about cat5 regarding signal quality or safety? If I continue with cat5, is it better to use a twisted pair (or more) instead of a single wire?
  2. Should an ESP32 drive this setup?
  3. Should I shift all signal to 5v, or just the ones that seem to need it?
  4. Is 330ohm resistors the right size? Can I add at the cpu side of the line, after the logic level shifter? does it matter where it goes? Why 330ohm?
  5. Should I place fuses on each line leaving the power supply? Can I use inline auto type fuses with lower gauge wiring (14ga)?

Thank you!!

#2
  1. CAT5 cable is not the best choice for addressable LEDs. Gauge of CAT5 strand is 23AWG for a good power delivery you need at least 18AWG, plus for signal better to have parallel wires. Eventually you can use existing cable with little loss of quality.
  2. ESP32 is preferred.
  3. Better use shifter for all outputs with data signal.
  4. Resistor should be in range of 33-62Ohm or no resistor at all
  5. Yes all power carrying wires better be fused. Auto type fuse is ok.
1 Like
#3

Thank you!

How is the 33-62Ohm size determined? Is it based on the type or amount of LED? CPU? wire?

#4

The resistor value is a little “black magic” value from experience.
The smaller value you can use reliably (preferably 0 ohm=> no resistor).
What kind of distance are you talking between the ESP32 and the strips?

For 5m and up I’d suggest adding a differential TxRx pair.
That will work perfectly with Cat5 cabling and replace the shifter.

#5

my long run is about 5m. How would I add a differential TxRx pair?

#6

For each strip you get a pair of RS485 modules one set to transmit (Tx) the other to recieve (Rx).
They power off 5V and take the GPIO data directly from the ESP32.
The Tx module sends the data across 2 wires (a Cat5 twisted pair is perfect for this) and the Rx module converts that back to a single data line at the strip location.

Here’s an example of the devices: RS485 modules
They’re designed specifically to deal with high speed data over long distances and can be used to transmit WLED data reliably over 100m.

1 Like
#7

Thanks for the explanation. I’m glad to know about this!

Is there any significant delay in the conversions or transmission? Ie, if I only need this on one or two of the 8 lines, will it be noticeable out of sync?

#8

There should be no delay, those devices are rated for at least 10Mbps, well beyond what the LED’s require.
You should be able to mix and match as you desire.

1 Like
#9

excellent.

Do the signals need to be upshifted to 5v to match the 5v working voltage of the module?

#10

No, they use a 5V supply but the Tx is compatible with 3.3V inputs and the Rx outputs 5V.

1 Like
#11

Which side of the signal wire should the resistor be installed:

Between the controller and the signal wire, or the signal wire and the LED strip?

And, does the direction matter?

#12

Typically goes at the controller end, but you can try at the strip.
Resistors have no direction (no polarity).

#13

Well, two of the 8 strips have a light flicker. They are oddly not the farthest out. I made a resistor wire harness and tested 10,33,47,100,330 ohm resistors on each side (one at a time). No change

I’ve got a set of RS-485 converters on the way.

#14

Amazon US recommended these and they looked slimmer. I have these now:. Robojax TTL to RS485 Module 485 to Serial UART Level Converter Communication Module https://a.co/d/fUzmfYc

Can I use these? Are the rx/tx pins for the “bridge”? Do they get crossed? Is A+ or B- for signal in/out?

#15

I have a prototype working. Super simple.

The bridge is connected over the long run with one of these on each side.
A+ connects to A+
B- connects to B-
Both boards get 5v/ground

The signal goes IN to the TX pin
The signal comes OUT of the RX pin on the other side.

I didn’t use the 2nd ground

Next step - install.

#16

And….

It works, installed. No more flash.

Sweeeeeeet!