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Eight-channel Darlington driver

ULN2803A Basic Circuit

Build a basic ULN2803A circuit with labeled pins, component values and connection guidance.

Package view

ULN2803A in a circuit

A physical 18-pin array switches the low side of a 12 V coil.

Controller D8 connects to I1 pin 1. A 12 V 240 ohm coil connects to O1 pin 18. COM pin 10 connects to plus 12 V; GND pin 9 joins the controller and supply returns. Inputs 2 through 8 are grounded and unused outputs are open.
All ground symbols share one return. The drawing shows the coil driver; relay contacts are not included.

Connect it, step by step

Follow the component values and pin connections

Wire the load

Connect the coil from +12 V to O1 pin 18 and join pin 9 to the common return.

Return flyback current

Connect COM pin 10 to +12 V at the load supply.

Control channel one

Drive I1 pin 1 HIGH to energize the coil and LOW to release it. Hold unused inputs LOW.

Component view