Basic Operation

This figure shows the basic storage unit locking and unlocking behaviour.

This SW1 is a switch ,and can be replaced by a microcontroller IO pin, as it's the one that controls the state a of the lock (represented by the Lamp L1).

The button represents the door's condition, and is a sensor for the storage unit door.

The OJ-SH-105HM is a 5VDC coil relay able to switch voltages ranging from 277VAC, 30VDC - Max.

The ULN2002A is a Darlington pair (load buffer or driver interface) for the relay; is a basic pair of transistors where the second transistor amplifiers the output current of the first transistor. This gives you a high current gain than a single transistor and allows the low voltage, low current output of a microcontroller to drive the high current relay; by either energize or collapse the magnetic field of the relays' coil when switch is in a high to, low state; causing the relay; to switch on or off.

Note

It's recommended that you view the IC's (Integrated Circuit) manufactures' datasheet, on all the components used in this design; before attempting to construct the circuit.

Note by: here we are switching a high voltage load(s), please be careful, and try to factor in the back EMF generated by the relay.

• Please remember to interface the diode between the ULN20002A and your relay(s); without it the back the EMF of the relay will blowout your IC components...