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Proximity Pilot

Overview~

The Proximity Pilot (PP) is the second signalling contact of a Type 2 connector. It tells the charger the current-carrying capacity of the attached cable, so the charger never advertises more current than the cable can safely carry. It is only relevant when the charger has a socket outlet (a detachable cable); a charger with a permanently attached cable knows its own cable and does not use PP.

A resistor built into the cable's plug, between PP and protective earth, codes the rating. The charger reads the resulting voltage on PP and maps it to a current.

Coded rating Typical use
13 A Low-power (granny) chargers
20 A Standard 16 A/20 A cables
32 A Common Type 2 cable

How it is used~

The PP contact is read through a divider into the ESP32 ADC. The measured voltage is compared against three thresholds to classify the cable as 13 A, 20 A or 32 A; anything below the 32 A threshold is taken as 63 A.

The reading is taken when the vehicle is plugged in, as the session begins (state B1). The resulting rating becomes an upper bound on the advertised Control Pilot current: the charger advertises the working charging current capped by the cable rating. So even if the maximum charging current is set higher, a 16 A cable limits the session to what that cable supports.

Socket-outlet mode requires a Proximity Pilot to be present on the board. With a fixed cable, PP is not needed and the maximum current is governed only by the configured maximum charging current.

Configuration~

PP is declared in board.yaml:

proximity:
  adcChannel: 2          # ADC1 channel sensing PP
  levels: [1650, 820, 430]   # thresholds for 13 A, 20 A, 32 A in mV

The three levels are the measured ADC voltages (in mV) at the 13 A, 20 A and 32 A boundaries; readings under the 32 A threshold are classified as 63 A. As with the control pilot, the exact figures depend on the board's divider and should be measured for your design.

If you're building an EVSE without a socket-outlet (having the cable directly attached) omit this configuration from board.yaml.

CAUTION

Working with high voltage is dangerous. Always follow local laws and regulations regarding high voltage work. If you are unsure about the rules in your country, consult a licensed electrician for more information.

See also~

  • Control Pilot – the line that advertises current to the vehicle.
  • Socket lock – mechanically retaining the plug in a socket outlet.
  • Charging control – how the cable rating caps the advertised current.