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?
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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?
If it is worth doing, it is worth OVER doing. - Mythbusters
Debunking Pseudoscience is fun!
Arctic White Roadster 2.5 #1200, S Sig Performance Vin# 227
That was a bust.
I was talking about the, just for example, 10-30 end to the California connector. THESE.
If it is worth doing, it is worth OVER doing. - Mythbusters
Debunking Pseudoscience is fun!
Arctic White Roadster 2.5 #1200, S Sig Performance Vin# 227
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.
Last edited by S-2000 Roadster; 08-30-2011 at 08:29 PM.
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.
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!Originally Posted by TEG
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)
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.
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 StationOutput Voltage 208 / 240V – 15A, single phase
• Input / Output Power 3.3kW
Level 2 - 160 Home Charging Station Cat. Nos. EVB22, EVB26 - 16A @ 120/240VAC, 60Hz
Last edited by TEG; 08-31-2011 at 02:18 PM.
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.
Last edited by W.Petefish; 08-30-2011 at 09:55 PM.
If it is worth doing, it is worth OVER doing. - Mythbusters
Debunking Pseudoscience is fun!
Arctic White Roadster 2.5 #1200, S Sig Performance Vin# 227
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.
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