24V / 5V BRIDGE

PLC to Arduino & VEX Interfacing Workbench

MCU Pin D2: HIGH (Pull-up)
SAFE_OPERATIONAL
Galvanic Isolation Boundary & Current Flow Schematic 24VDC ↔ 5VDC ISOLATED
24V PLC DOMAIN 5V MCU DOMAIN PLC OUTPUT 24V (OFF) 1.5kΩ (1/2W) PC817 OPTOCOUPLER PLC COM (0VDC) 4.7k Pullup +5V MCU ARDUINO / VEX PIN D2: 5V (HIGH) Active-Low Logic MCU GND (Isolated)
Calculated Series Resistor
1520 Ω
(V_in - V_f) / I_target
Nearest E24 Standard
1500 Ω
Standard 5% Component
Actual Forward Current
15.2 mA
Diode I_f @ Standard R
Resistor Power Dissipation
346.56 mW
Exceeds 1/4W (250mW)!
Recommended Resistor Rating
1/2W (0.5W) minimum
Thermal safety headroom
Propagation Delay & Logic
18 μs
Active-Low Inverted
DUAL-CHANNEL LOGIC OSCILLOSCOPE (CH1: 24V PLC OUT [ORANGE] | CH2: 5V MCU PIN [TEAL]) 10 Hz Auto-Pulse
Rockwell Studio 5000 / CCW Ladder Rung
XIC(Run_PB) OTE(Opto_Out_0);
Arduino / VEX V5 Embedded C++ Firmware
const int OPTO_PIN = 2;
void setup() { pinMode(OPTO_PIN, INPUT_PULLUP); }
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