How to Quickly Set the Time: Measure the voltage (Uc) across the resistor. For example, on a 5V 15min module, if Uc=2V, then time = 2V/5V * 15min = 6min. This relay module is commonly used in timer-controlled equipment, machine repetitive test circuits, aquarium intermittent pumps, etc. This 12v timer switch is a high-precision timing relay module with stable and reliable performance. The settable time interval is very wide, with adjustable on-time and off-time. The 12v relay timer is highly suitable for controlling reciprocating stroke lengths or repeated on/off cycling of equipment and product aging tests. Supports 2 modes: mon-mode (one-time) and cycle mode, easily switchable via jumper adjustment. Quantity: (1-pack) Timer Switch Relay Module. Other products are not included. Size: 70*20mm (for reference only). Color as shown.