GTEM ESP32 ATM90E26 – Connections

The GTEM, Grid Tie Energy Monitor board, has been designed to be flexible and whilst providing Energy Monitoring functionality, it also has other options for experimenting.

• AC Input
  • Power safely derived from a SELV / Wall AC/AC Power Supply
  • Provides AC waveform reference for accurate Real Power measurements
  • Connect ideally 12V AC (can be slightly lower), to the AC/DC In terminals. (It does not matter which way round the wires go).
  • DC will power the board but not provide ATM functionality such as AC Voltage or Mains Frequency
  • The AC will then flow into a half-wave rectifier and to a 3V3 SMPS.
• I2 Input
  • 120uV to 600mV RMS (When Gain is 1)
  • This is generally normally unused.
• CT Clamp
  • Typically a YHDC SCT-013 100A/50mA Current Transformer
    • These current transformers can measure current up to 100A
    • Can fit around cables that are 13mm in diameter
    • They have 3.5mm jacks which plug directly into the GTEM
    • A TVS diode is generally built in for safety, and to prevent open circuiting
    • These output 50mA when reading 100A RMS
  • Connection is a 3-Pole 3.5mm Socket
    • Centre ring not used.
• User GPIO
  • GPIO 12 – Input or Output
    • Note: Must be LOW at ESP Boot
  • GPIO 14 – Input or Output
• OPTO Input
  • GPIO33 – Input or Output
    • Example devices 3DU5C, TSL257 or GL5528
  • Could be used for monitoring Meter Pulses
• USB
  • Micro USB Connector
  • GTEM board is WeMos D1 Mini flashing compatible
    • Set the BOARD to ESP32, ‘WEMOS D1 MINI ESP32’ DEV Module (or similar).
  • You can also set the BAUD rate to 921600 to speed up flashing
• I2C/OLED
  • I2C Expansion
  • Standard OLED connections
    • Ground / 3V3 / SCL / SDA