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?
I suspect that it has to do with a resistor, but what else?
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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!"Keying" by shape of the metal ring seems far fetched to me.
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.
Output 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
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.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?
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.
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.
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.
Thanks for the report, Sam. Even if the UMC is totally different, this is still very interesting for RFMC repairs or upgrades.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.
here 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).
Yep... But does the UMC work in the same/similar way to the RFMC?
I can't tell from the pictures how the UMC knows which plug is attached.I opened up my 14-50 adaptor end.