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Card Reader Current Draw

Access Control PSU Sizing · OSDP / Wiegand

When to use: Size the access-control power supply by summing the DC current of every connected device — readers (OSDP/Wiegand), request-to-exit (REX) sensors, door contacts, electric strikes or mag-locks, and the controller board. Add a margin for inrush and simultaneous unlock, then pick the next standard PSU amperage above the total.

Supply

System Voltage

Inrush Margin

Connected Devices

Device

Qty

440 mA

Device

Qty

120 mA

Device

Qty

1000 mA

Device

Qty

350 mA

Total Current (with margin)

2.39 A

Recommend ≥ 2.5 A PSU at 12 VDC

Results

Raw Total Current1.91 A (1910 mA)

With 25% Margin2.39 A

Total Power28.6 W

Recommended PSU2.5 A

System Voltage12 VDC

Notes

Currents are typical; verify against device datasheets

Locks draw peak inrush at energize — margin covers this

Account for voltage drop on long lock runs (18/16 AWG)

Add battery backup load to PSU sizing (see UPS calculator)