TapHome

Optical Bus Isolation

Galvanic separation of RS-485 and Modbus buses with a bidirectional optical isolator. Basic ESD protection on the SLAVE side; the SLAVE side needs its own power supply.

Optical Bus Isolation

The bus can also be separated with a bidirectional optical isolator. This provides full galvanic isolation between two power systems, provided that the SLAVE side has its own power supply (see below). On the SLAVE side, the isolator is also equipped with basic ESD protection (pulse up to 600 W), intended for RS-485 or Modbus bus data transmissions. It is not a surge protector for lightning currents.

When to Use Optical Isolation

We recommend this type of isolation whenever the cabling is located in places where it could be mechanically damaged. Such places are also more exposed to voltages induced directly into the systems.

It’s useful to use the bus isolator:

  • To amplify the signal – as a signal shaper on long buses
  • In case of mechanical damage – when the cabling is in high-risk locations
  • In case of induction problems – where there is a risk of direct voltage induction
  • In case of communication problems – where reverse voltage waveforms, interference, or reflections occur on the bus data cables for unknown reasons

Important Notice

The bus isolator does not fully provide overvoltage protection.

The bus isolator isolates the master and slave from each other, but does not divert the induced voltage to the PE terminal. Where the bus leaves the protective zone of the lightning protection system, surge protection is also required.

Power Supply of the SLAVE Side

The isolation works only if the device on the SLAVE side is powered from a different power supply than the MASTER side (TapHome Core and modules). If both sides share one 24 V power supply, the power supply wiring bypasses the isolation.

The isolator is installed on the MASTER side, typically next to the TapHome Core, as close to it as possible.

Connection Diagram

Separate line with two power sources

The diagram shows a separate line with two power sources and an optical isolator.

Technical Specifications

  • Type of isolation: Galvanic optical isolation
  • Overvoltage protection: basic ESD protection on the SLAVE side (pulse up to 600 W)
  • Power supply of the SLAVE side: its own power supply, separate from the MASTER side
  • Supported protocols: RS-485, Modbus RTU
  • Type of communication: Bidirectional
  • Function: Power system isolation, signal shaping