AC Mains Voltage Sense Input - DitroniX/IPEM-IoT-Power-Energy-Monitor GitHub Wiki

The IPEM IoT Power Energy Monitor boards, have been designed to be flexible and whilst providing Energy Monitoring functionality, it also has other options for experimenting.

The boards have a four input terminal block, which allows you to provide a low voltage AC 'signal' which is used by the ATM90E36 to synchronise the mains electricity sinewave and determine the flow of energy, i.e. import and export.

A low voltage AC signal (8 to 12V AC RMS), is typically provided, for safety reasons, via SELV mains transformer.

Most users use a Bell Transformer, such as a GreenBrook DAT01A. or TLC TC TR7. You could use a 'wall wart' type power supply but this MUST be an AC _transformer _type and NOT a switched mode.

Inputs

These low voltage AC signal connections go to the ATM90E36 ATM_V1P, ATM_V2P and ATM_V3P inputs.

The AC inputs are used for sensing the mains 50Hz to 60Hz sinewave and from this, the ATM90E36 can detect, along with monitoring the current AC sinewave, the direction of current flow. For example, importing energy or exporting energy.

Connections are:

  • 1 - Phase 1
  • 2 - Phase 2
  • 3 - Phase 3
  • COM - Common

AC Voltage

The AC input voltage needs to be roughly 8V to 12V, with a maximum of around 20V RMS.

  • If the input is too low, the AC waveform can get noisy and not get detected correctly leading to erratic voltage readings.
  • If the input is too high, the AC waveform can get noisy or distorted and not get detected correctly leading to erratic voltage readings.

Transformer Connections

Transformer Connections PDF

Single Phase

This is the typical house or office, where you have a single phase supply.

In this 'mode' the board is able to monitor three separate circuits, all on the same phase. An example is the house, inverter and garage.

Connections

When using single phase mode, you MUST connect/ short, inputs 1, 2, and 3 together. This then allows the same AC main Sinewave across all inputs.

A solder pad is provided on the bottom of the board which does the same thing. Simply solder 123 together and use any AC input.

The other side of the low voltage transformer will go to the COM (common), connection.

Split (or Dual) Phase

This is a typical house or office in the USA, where two 110-115V AC supplies are brought into the premises.

For split phase to be correctly measured, you will need to use the DIP Switches to configure to SPLIT PHASE.

Connections

Two, low voltage transformers will be required for split phase, one on each input.

In this instance, ONLY inputs 1 and 3 are used. This applies to both low voltage AC signal connections and current transformer inputs.

Three Phase

This is typically for commercial or industrial use, where a full three phase supply is used.

Three phase can be:

  • Three-phase three-wire (3P3W, Y or Δ)
  • Three-phase four-wire (3P4W, Y0)

In this instance, three low voltage transformers will be required, once for each phase.

Connections

When using either three-phase mode, you MUST connect a separate AC input from each phase. This means a separate transformer, one on each phase. With the common of all three transformers going to common.

This then allows an individual 120 degree AC main Sinewave on each input, which corresponds with the separate CT clamps on each input.

Three-phase four-wire (3P4W, Y0) When measuring three-phase four-wire (3P4W, Y0) circuits, you will need to use four CT Clamps. One on each phase and one on neutral.

Reading Errors

Should you notice errors in your reading readings, it is worth double checking the connections.

Import Export Wrong Way

This is cause through through the CT Clamp and AC input being 180 degrees out.

Simple reverse either the AC input(s) polarity, or turn the CT Clamp direction 180 degrees.

Wrong Voltage

This can be caused by:

  • AC Low Voltage Input too low (or too high.