Button Interface Strategy

The elevator call button operates on a 24V control circuit.

Instead of modifying the control board, the relay was wired in parallel across the button terminals.

When activated, the relay momentarily shorts the terminals, simulating a button press.

This method ensures:

• No firmware-level integration with elevator controller
• Electrical isolation via relay
• Minimal intrusion into existing circuitry

Power Evolution

Iteration 1 & 2

• Powered via USB power bank
• External wiring visible
• Prototyping stage

Iteration 3

• Identified unused 24V rail in lift power supply
• Integrated DC-DC buck converter
• Removed dependency on external battery

This significantly improved deployment cleanliness and reliability.