Search results

  1. HellasTechn

    RS422/485 and ground wire.

    Maybe they use the metal housing of the usb for that purpose.
  2. HellasTechn

    How can I bypass a switch on a humidifier?

    Hello. You provide with very little information. You could start with brand, model, the sensor you are using... mains power ? Obviously it was not ment to be used that way. I suspect that you may need to interface with the units microcontroller to be able to operate it the way you wish. You...
  3. HellasTechn

    RS422/485 and ground wire.

    I keep on reading on the net about this issue and it seems like i keep stumbling on different opinions. Others say that a return line has to be used or ground can act as return line. Interesting is what the following youtube video says at 03.00 about ground loops that can corrupt data. How can...
  4. HellasTechn

    RS422/485 and ground wire.

    i did. Bottom line is that the system may work with only one twisted pair of wires but it is strongly recommended (given that all grounds are okay) that a common ground is used. And from what i understand if this common ground is connected to the shielding of the wire, even better.
  5. HellasTechn

    RS422/485 and ground wire.

    Is that correct ?
  6. HellasTechn

    RS422/485 and ground wire.

    If my thinking is correct then in the below circuit we should be fine since in theory no ground loop would exist if say both transformers where fed from the same mains socket. Only when the two circuits where to be powered from other power sources that may give the same potential difference but...
  7. HellasTechn

    RS422/485 and ground wire.

    Yes, forgive me im confused over this. So indeed some people say it has to exist while other say that there is no need for it to be there since the devices have their own ground. Not using a common ground does make sense to me when we only measure the potential difference between 2 lines and we...
  8. HellasTechn

    RS422/485 and ground wire.

    As if i was to put my dmm with its negative lead to A line (always used as ref point) and its positive to B line and get reading ranging from -5V to + 5V ?
  9. HellasTechn

    RS422/485 and ground wire.

    True. So there may be some tiny ammount of current flowing due to non ideal conditions ? Is that why they say that the A and B lines do not serve as return lines ? It says: A two wire system then requires two twisted pairs and a four wire system requires three twisted pairs. Meaning that is 2...
  10. HellasTechn

    RS422/485 and ground wire.

    I really dont want to cause you a headache. I really try to understand. How is it possible ? there is no potential difference between the + of battery A and the + of battery B. Note that only the - sides of each batterys are tied to GND. and the resistor in that picture is not connected to it...
  11. HellasTechn

    RS422/485 and ground wire.

    Please excuse my confusion. I either have things mixed up in my mind badly or i am missing alot. I read that in the rs422 standard the 2 conductors are one way only conductors. In my mind i picture it like the diagram i attach below. How can current return to the power source if some short of...
  12. HellasTechn

    RS422/485 and ground wire.

    I think I understand but I can not imagine how signal can pass from one point to another without completing circuit some how
  13. HellasTechn

    RS422/485 and ground wire.

    I beleve they take it for granted that there will be common ground. Just like they take it for granted that there is VCC thus they just not show it on their diagrams. I found this pdf on www.robustdc.com On page 4 it says : Data communication systems involve connecting multiple "systems"...
  14. HellasTechn

    RS422/485 and ground wire.

    Here is the thing, though they do not show any common line, they dont show any VCC either. That doesnt mean that there is not any. Maybe in these diagrams they assume that VCC and GND is common for all.
  15. HellasTechn

    RS422/485 and ground wire.

    about a year ago i was testing an rs422 to uart converter chip powered from my bench psu (not earthed) with an rs422 gps receiver powerd from an smps wall wart (also not earthed). i remember clearly that it would work with either the A and B line connected or with only B line and both grounds...
  16. HellasTechn

    RS422/485 and ground wire.

    Say i have a battery powered rs422 devise and want to talk to an other battery powered rs422. No ground between them. This will never happen if i do not use the A and B lines plus a 3rd line as common ground. Yes
  17. HellasTechn

    RS422/485 and ground wire.

    Yes that’s exactly what ground plane does but in this case i believe the text is referring to the A and B lines. In other words that at a given time one acts as tx and the other as return.
  18. HellasTechn

    RS422/485 and ground wire.

    Interesting what Wikipedia writes about this. https://en.wikipedia.org/wiki/RS-422 RS-422 specifies differential signaling, with every data line paired with a dedicated return line. It is the voltage difference between these two lines that define the mark and space, rather than, as in RS-232...
  19. HellasTechn

    RS422/485 and ground wire.

    Greetings dear friends. Today I was reading about RS422/485 protocols. I do know that these are differential line but that raise a question. Do they really need an extra signal ground wire or not ? Ive seen it many times used without a ground wire, just the data + and data- lines. How does the...
  20. HellasTechn

    Creating a user interface for arduino.

    Thanks. For the time being i have put this project into the freezer. I will read carefully about debouncing and how to properly implement it after i get back to it :)
Top