Servos, LCD displays, and relays are output devices that convert signals from a digital system into controlled movement, visual information, or switching of another electrical circuit. Selection depends on the required output and operating conditions.
In an input-process-output system, a processor such as a microcontroller receives input data, follows programmed instructions, and sends control signals to an output device. The device then produces an observable or useful response.
| Output device | Function | Selection considerations |
|---|---|---|
| Servo | Produces controlled rotational movement. Pulse-width modulation moves and holds the shaft at a specified angular position. | Angle, torque, speed, positional accuracy, operating voltage, load, and power consumption. |
| LCD display | Converts processed data into visual output, including text, numbers, symbols, or graphics. It can use a parallel or serial interface. | Size, resolution, viewing angle, readability, colour, refresh rate, interface compatibility, and energy consumption. |
| Relay | Uses a low-power signal to open or close contacts in a separate circuit, allowing a controller to switch motors, lamps, or heaters. | Coil voltage, contact rating, switching speed, electrical isolation, lifetime, size, and driver requirements. |
A microcontroller may be unable to power a relay coil or high-torque servo directly. A driver circuit, separate power supply, and protective components may therefore be required. For example, a flyback diode protects control electronics from the voltage generated when a relay coil is switched off.
A common misconception is that every digital output device has only two states: on and off. Relays commonly operate this way, but digital signals can encode complex instructions. Servos receive position commands, while LCDs receive data representing changing text or graphics.
For , identify the device's function and justify its selection. Connect its capabilities to the design specification, electrical load, operating environment, power requirements, and user needs rather than merely naming the component.
