Livolo, serial, no RF



  • The livolo switches I have are not rf, Im wondering if anyone has had success connecting an arduino (or other) to the pads for the rf module on the board? I tried to connect an ftdi to it and let all the magic smoke out of the livolo. Wiring mistake most likely. I did find a project where the pic was reprogrammed to give serial, but I was hoping to just feed the remote codes to the board via an arduino.

    I do see projects here that create a new board, but im finicky and would like to keep it mostly stock.

    It looks like tx pad connects to tx on the pic, and DER connects to rb6, I'm guessing I picked the wrong line for ground. Oddly my ftdi still works, even though there was a loud snap, and lots of soot on the board.



  • Man, you almost killed yourself. The ground in the livolo board is actually referenced to the LIVE wire. Check the continuity between L and any GND pin (ej. 2nd pin of the RF connector, next to the antenna one) to see it yourself.

    If you connect the livolo to a PC via a FTDI, you are electrifying your computer's case.

    Sorry to resuscitate the thread, but I think it was worth mentioning.


  • Hardware Contributor

    @wallyllama

    If you want to repeat (although I don't recommend) this experiment better use some optocouplers instead. This way live wire and ground on the other side is not connected physically.



  • I found that out, it has to do with how they pull power when the switch is off. I did get some optocouplers, i did get some results, but I havent make it work yet. I did find the difference of regular and 2way is a diode and resistor. (And the buzzer). Oh and like Tesla and edision, the rule is to work with one hand behind my back when AC is live.



  • I found that the optocouplers draw more current than the power supply can deliver and so the voltage drops and the PIC either hangs or reboots itself.

    I'm also trying to send commands to the livolo (and get status from it) while keeping it as stock as possible. I'm reprogramming the PIC with my own firmware, though. Here is what I've got so far:

    https://forum.mysensors.org/topic/7151/livolo-firmware-mod


  • Hardware Contributor

    @javizzz

    The Livolo power supply is a sensitive topic and it's special by its nature. Being a live wire only design it requires some special design and it cannot deliver high currents - at least not in standby mode when the light is off.

    I've struggled with it along with @tonnerre33 and still working on a solution but not without some hacks unfortunately.

    But getting back to this topic issue(s): aren't there some low current optocouplers available? The part that draws more current is the LED from it as far as I know. And for strong coupling/better transfer ratio the LED might require more current.

    I found this one for example: ACPL-M61L from Avago. They claim that it works at 1mA and even less.



  • I am mostly trying to push data to the livolo, so the power to drive the optocoupler was coming from my ftdi. Inassumed (wrongly?) that with a reisitor the data pin was vbing driven about the same as if a radio module was there.


  • Hardware Contributor

    @wallyllama

    For sending data then yes the led from optocoupler is powered by the ftdi. The output stage of the optocoupler which is usually a transistor draws power from Livolo but it doesn't need to be high in order to work. I think even 1mA should be enough so the collector resistor should be tuned for that value.

    Rc = (Vcc - Vcesat) / Ic => (3.3 - 0.6)V / 1mA = 2.7Kohm

    The above ecuation came in my mind for 3.3V logic... hope I didn't missed something - well excluding the current draw by the PIC mcu uart rx input pin which should be very small compared to 1mA.

    I think that on the Livolo board the mcu has a 3V supply actually so the resistor would be around 2.4Kohm - but it's not critical so 2.7Kohm should be ok too. Vcesat varies too as other transistor parameters in general.



  • @mtiutiu I also assumed that I can spell and proofread. Thank you for this info. It is more helpul than a month of reading google translated russian sites about livolo.


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