Can SwitchBlox Industrial convert a 12 V input to 24 V or 57 V passive PoE?

BotBlox Hardware
1

This topic was migrated from the BotBlox ticketing system after being summarized and anonymized.

Question

Can SwitchBlox Industrial accept power from a 12 V DC battery and provide passive PoE to a connected device?

Can the output voltage be configured independently—for example, supplying the board with 12 V and selecting either 24 V or 57 V passive PoE on one of the Ethernet ports?

Answer

SwitchBlox Industrial supports selectable passive PoE injection, but it does not convert the input voltage.

When passive PoE is enabled for a port, the board passes its supply voltage through to that port. The DIP switches control which ports receive power; they do not select or change the PoE voltage.

For example:

  • 12 V DC input provides approximately 12 V passive PoE.
  • 24 V DC input provides approximately 24 V passive PoE.
  • 57 V DC input provides approximately 57 V passive PoE.

Therefore, a 12 V input cannot directly produce 24 V or 57 V passive PoE. An external DC-DC boost converter would be required to raise the supply voltage before it reaches the switch.

Does the board support active PoE?

Most BotBlox active PoE solutions require a supply in the 48–60 V range. Active PoE and passive PoE operate differently:

  • Active PoE detects and negotiates with a compatible powered device before applying power.
  • Passive PoE applies the selected supply voltage directly to the Ethernet power conductors without negotiation.

SwitchBlox Industrial’s selectable feature is passive PoE injection. It should not be treated as an active PoE voltage converter or power supply.

Example configurations

Powering a 12 V passive PoE device

A 12 V battery can power SwitchBlox Industrial directly. When passive PoE is enabled on the required port, approximately 12 V is passed through to the connected device.

Powering a 24 V passive PoE device from a 12 V battery

A DC-DC converter must first raise the battery voltage from 12 V to 24 V. The converter’s 24 V output can then supply the switch, which passes 24 V through to the selected passive PoE port.

Powering a 48–57 V PoE device from a 12 V battery

A suitable DC-DC converter or PoE power stage is required. The correct implementation depends on whether the connected device expects passive PoE or standards-compliant active PoE.

Important checks before enabling passive PoE

Because passive PoE does not negotiate with the connected device, confirm the following before enabling it:

  • The device supports passive PoE.
  • The device accepts the supplied voltage.
  • The PoE conductor assignment and polarity are compatible.
  • The switch, cabling and power supply can support the required current.
  • The input voltage remains within the operating limits of SwitchBlox Industrial.

Applying the wrong passive PoE voltage or pinout can damage the connected equipment.

The main point is: SwitchBlox Industrial selects where passive PoE is applied, but the PoE voltage is determined by the board’s input supply.