Today, a novice engineer approached me with a question: he wants to develop an alarm panel and is looking to use PoE to enable a single Ethernet cable to provide both power and data transmission. He hasn’t been able to find a PoE module and would like to know if this is feasible.
His key requirement is for the alarm panel to operate using just a single Ethernet cable, which is, of course, entirely possible; this is a standard application of PoE technology.
Returning to his question, this solution can be integrated onto the PCB using a PoE module, though I would recommend using an integrated RJ45 connector (a version with PoE functionality) in conjunction with an external PD chip, as this reduces PCB layout work and, once soldered, allows power and signals to be routed to the main control chip via the connector's pins.
The PoE Power Supply Process
- The PSE first transmits direct current via the network cable.
- The PD device (alarm panel) feeds the power into the PoE power transformer at the rear via an integrated RJ45 connector.
- The PoE power transformer, in conjunction with the controller, converts the 48V high voltage into the low voltage (5V/12V) required by the alarm panel, thereby supplying power to the main controller and sensors.
Given that the alarm panel does not have high speed requirements, I have compiled a list of a few components as examples for your reference, based on the requirements.
- 100 Mbps integrated RJ45: SYT111B032DB1A1DPQ
- Depending on the device's voltage and power requirements, two PoE power transformers are recommended: (1) 5V/12W: ST-0880WHB (2) 12V/13W: WH13P-12L If your aim is to learn how to design a PoE circuit, VOOHU's reference design is an excellent starting point. If your aim is to quickly build a functional alarm panel, a PoE-enabled development board or a ready-made PoE splitter remains the more straightforward option.
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