When talking about long data lines, is it the length from the ESP32 data pin to the first LED in the run or the LAST LED in the run?
I’m using RS485 from one side of the house to the other but, to simplify installation, the distant end RS485 transceiver may be up to 10 feet from the LED strip. Will this distance be an issue with 18-3 wire (12v plus data) from the RS485 box to the LED strip?
The strips themselves are ~15 feet.
Thanks
It is the distance to the first LED. Each one after that only sees a line equal to the length from it to the previous LED, usually a couple centimeters.
10ft isn’t far so probably it will just work. I do recommend using twisted pair wiring from the receiver to the LED and a separate (thicker) copper wire pair to your 12v power supply to further reduce the odds you run into problems.
Why twisted pair when only one is used? Would you ground the other to act as a pseudo shield?
For that matter, I could run 18-2 for power and 20-1 shielded for data.
You ground the 2nd line to ensure that the data connection references the same level as the ESP32 that transmit it. In general, a 10’ data line shouldn’t be an issue.
Sending data requires two wires, one for the outgoing current of the signal, the other for the returning current so you are using two wires. Putting the two wires together gives best signal integrity and reduces the odds of problems if wires cannot be kept short.
in my case, I have rs845 between the ESP32 and distant end.
Distant end RS485 is powered by a 12volt buck. 12v +/- are also sent along to power the LED which is giving the LED strip the same ground reference as the RS485rx chip.
So far, it’s working without a common ground reference between the two RS485 chips which I think is correct but I’m testing with short distances.
POE->ESP32 → RS485tx → 100ft run → RS485rx → 10ft run → LED Strip
Definitely little chance of error there, the RS485 Rx (probably a MAX485) chip is a good TTL driver.
The ground reference in this case is between the Rx board and the LED strip it’s driving. If you have a 12V->5v buck converter at the Rx end, you can effectively remove the 100’ ground wire if you wish. The ground from the BC to the Rx board becomes the common ground.
Once you’ve powered each Tx and Rx board with 5V, your “distant” data is handled by the requirements of the TxRx boards: a single pair of wires and proper termination on the boards.
Data transfer over the A/B wires is not the same as for typical ESP GPIO->LED setups (and that’s why it’s more reliable). In this kind of setup, I would definitely suggest RS485 boards with A/B line protection builtin (TVS diodes/serial fuses) to deal with possible ooops moments while wiring.