void loop() digitalWrite(2, HIGH); // Relay1 ON delay(1000); digitalWrite(2, LOW); // Relay1 OFF digitalWrite(3, HIGH); // Relay2 ON delay(1000); digitalWrite(3, LOW); // ... similarly for channels 3 and 4
Most modules feature optoisolators (like the 817C) to electrically isolate the sensitive microcontroller side from the high-power relay side, preventing electrical noise and damage.
While Proteus includes basic relay components (e.g., RLY-SPST , RLY-DPDT ), these don’t represent the actual 4-channel relay modules used in real life—complete with optocouplers, transistor drivers, LED indicators, and a 3-pin control interface (VCC, GND, IN1–IN4).
Start the simulation to verify that the relay switches on/off in response to the input signal. Example Project: Arduino 4-Channel Relay Control
Proteus requires specific external files to recognize and simulate new components. Custom libraries consist of two primary file types.
"No transistors?" Sarah asked, leaning in. "Where are the drivers?"
: Typically located at C:\ProgramData\Labcenter Electronics\Proteus 8 Professional\Data\LIBRARY . Note: ProgramData is a hidden folder by default.
Adapted from source code for Arduino 4 channel relay control
Repeat COM2/NO2/NC2 for channels 2,3,4.
Optocouplers isolate low-voltage control circuits from high-voltage load lines to prevent electrical noise and damage.