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UMC Wiring

Discussion in 'Roadster: Technical' started by W.Petefish, Aug 30, 2011.

  1. W.Petefish

    W.Petefish Active Member

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    Does anyone know how the current revision of the UMC detects the current available from the adaptor?

    I suspect that it has to do with a resistor, but what else?
     
  2. W.Petefish

    W.Petefish Active Member

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    That was a bust.

    I was talking about the, just for example, 10-30 end to the California connector. THESE.
     
  3. S-2000 Roadster

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    #4 S-2000 Roadster, Aug 30, 2011
    Last edited: Aug 30, 2011
    The 'manual' for the UMC shows that there are conductive metal rings on the changeable part of the adapter. The rings vary in size, and evidently make contact with an array of conductors. There appears to be a unique ring shape, size, and placement for each possible current rating. Since the various physical plugs on the ends of the adapters each have a standard maximum current rating, Tesla Motors simply builds the adapter cables to match the standard maximum current rating with the appropriate metal ring. I am not aware of anyone else doing this, so I doubt that you can buy those rings anywhere else.

    So, basically, it doesn't literally detect the available current (that would be impossible anyway), but rather it is 'keyed' with a conductive metal key that corresponds to the standard maximum current rating of the attached physical plug standard.

    The bigger, 'smart' end of the UMC has all the brains to detect the metal rings and 'know' which physical plug is attached. The brain then generates the correct electronic pilot signal for the Roadster. In effect, the bump in the cable converts between physical keying and electronic signaling.

    Note: There might not actually be any resistors in this part of the keying. There are certainly resistors in other subsystems of the charger, but they're not necessary for this part (unless they use resistors to reduce the number of input pins on the embedded processor).

    P.S. If a 'standard' receptacle is improperly wired to the wrong breaker, the UMC will still announce the assumed maximum current, not the actual maximum current.
     
  4. TEG

    TEG TMC Moderator

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    I know how the old RFMC does it (pre-dating the Tesla UMC), but I would assume the Tesla UMC does something similar with different resistors and/or diodes to let the "brains" know what kind of plug end you have attached, and it will then send an appropriate pilot signal to the Roadster. "Keying" by shape of the metal ring seems far fetched to me.
     
  5. S-2000 Roadster

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    This could be another one of those technical details of the Roadster explained to me by my salesman which turned out to be way off from the actual technology. It sure seemed ingenious (if not expensive) when it was described to me in detail!

    I only have one UMC adapter cable - the one that's included. Looking at the photos I can only see two variations (3 with a visible metal ring that matches and the other 5 with no visible metal ring). So now I have no way to confirm what I was told (and took on faith, coming from a Tesla employee).

    I was also told that the giant 400V supply under the front hood for the HVAC was instead responsible for running the 12V accessories. Much later I learned that the 12V supply is elsewhere and the 400V comes directly from the ESS and is delivered to the HVAC system without any significant 12V involvement.

    Does anyone have all of the UMC adapter cables? (actually, I seem to recall that a few members here got the full collection)
     
  6. Doug_G

    Doug_G Lead Moderator

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    I was thinking of taking my NEMA 14-30 UMC adapter and replacing the plug with a J1772. That would be less expensive, and actually available, compared to the Tesla adapter. It would be limited to 30A but that's what most of the chargers are anyway.
     
  7. TEG

    TEG TMC Moderator

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    #8 TEG, Aug 30, 2011
    Last edited: Aug 31, 2011
    Sounds like a good plan.
    But you would ignore the pilot signal from the J-plug.
    There are some 15A/16A J-plugs out there - so make sure to turn down the charge rate from the VDS first...

    https://www.homecharging.spx.com/volt/pdf/GM10-463.pdf
    Evr-Green Home Charging Station, Level 2, 3.8kW output, EVB22-3PM : Home Charging Station
     
  8. W.Petefish

    W.Petefish Active Member

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    #9 W.Petefish, Aug 30, 2011
    Last edited: Aug 30, 2011
    Doug_G, take apart the 14-30 end. Look for any resistors and/or diodes. Then take apart the california end and look for the same. Pictures would be nice.

    From what I saw on the 14-50 end, the purple/blue wire (I don't remember the color exactly) was connected to the green ground.
     
  9. scott451

    scott451 KWH-PWR#1349Sprt,S Sig#96

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    Martin's RFMC design used a diode and a 90C thermal switch. My guess is that the UMC works the same way. The other possiblity is that is uses a dallas one-wire eeprom on the unused neutral pin of the california connector.
     
  10. W.Petefish

    W.Petefish Active Member

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    The neutral pin you mention is used for the blue/purple wire. Which on the UMC's 14-50 is grounded through a fuse.
     
  11. Doug_G

    Doug_G Lead Moderator

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    I haven't taken it apart, but the California connector has four connections. The outer shell connects to the NEMA 14-30 ground pin, as expected. Two of the slots connect to the hot pins on the NEMA. The third slot is, as far as I can tell, open circuit. Presumably this pin is used for signalling. I'd have to open the California connector to find out.
     
  12. samcarney

    samcarney Sam C

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    I purchased an RFMC before the Tesla UMC was available. It arrived with a 5-15, 10-30, and 14-50 adapter. I immediately disassembled the 14-50 and 10-30 adapters to reverse engineer.
    I found that on the "California" side all 4 wires (black, red, white, green) are all connected to pins on the the California plug.
    On the opposite end the black and red wires are connected to the pins on the 14-50 and 10-30 plug that conduct the charging current.
    The green wire is connected to the ground pin on the plug.
    The white wire is not connected to a pin on the plug.
    There is a diode that is connected between the green and white wires. The orientation of the diode determines whether it is a 30 or 50 amp plug.
    If the RFMC does not detect a diode (open circuit) it defaults to 16 amps.
    There is also a thermal switch connected between the white and green wires. If the plug gets hot due to a bad connection etc. the switch closes and stops the charging.

    So it appears that a diode connected between green and white ( I don't have my notes with me and can't remember if the positive side of the diode goes to the white wire to indicate 50 amps or 30 amps or vice versa).
    An open circuit between green and white indicates 20 amps.
    A short circuit between green and white indicates trouble and stops charging.

    There was a posting by Martin Eberhard with a description of operation and schematics for the RFMC which helped immensely. (sorry don't have the link available either).

    With this information I was able to gather the parts to build and test adapters that will allow me to plug into most receptacles in North America.
    In addition to the 5-20, 10-30, and 14-50 that came with the RFMC I also have;
    L5-30, 6-15, 6-20, 6-30, 6-50, 10-50, and L14-30 adapters. I built a 22 foot long 4-conductor #6 guage wire extension cord for those out of the way receptacles. I also have a cable with a "California" end on 1 side and stripped wires on the other side(pigtail) that can be connected directly to a fuse or breaker panel.

    I am fairly confident I can find a compatible "plug" on road trips, I just can't take a lot of luggage
     
  13. TEG

    TEG TMC Moderator

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    Yep... But does the UMC work in the same/similar way to the RFMC?
     
  14. Doug_G

    Doug_G Lead Moderator

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    I used a DVM in "diode mode" and didn't see anything. It's possible that I simply didn't make contact, as it's hard to reach inside the slot, but I tried several times. I'll check again, but it's quite possible that the UMC works differently. As Scott said, they might use one of those "one wire" gadgets from Dallas.
     
  15. S-2000 Roadster

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    Thanks for the report, Sam. Even if the UMC is totally different, this is still very interesting for RFMC repairs or upgrades.
     
  16. W.Petefish

    W.Petefish Active Member

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    I opened up my 14-50 adaptor end. (gotta love the 8MP cellphone camera)

    IMAG0245.jpg
    IMAG0246.jpg
     
  17. suxxer

    suxxer ElektroVolt

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    Well, here's the document from Martin...

    RFMC_01_Page_13.jpg RFMC_01_Page_14.jpg RFMC_01_Page_15.jpg RFMC_01_Page_09.jpg RFMC_01_Page_10.jpg RFMC_01_Page_11.jpg RFMC_01_Page_12.jpg

    Or the PDF:
    View attachment MArtin_Eberhard_Mobile_Charger.pdf
     
  18. W.Petefish

    W.Petefish Active Member

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    From what I'm seeing, no.
     
  19. TEG

    TEG TMC Moderator

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    #20 TEG, Sep 2, 2011
    Last edited: Sep 2, 2011
    I can't tell from the pictures how the UMC knows which plug is attached.
    Anyone see somthing?
    (I wonder where the maroon/purple wires go.)
     

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