Segment Pin Function a 7 Segment A b 6 Segment B c 4 Segment C d 2 Segment D e 1 Segment E f 9 Segment F g 10 Segment G DP 5 Decimal Point Common Cathode 3, 8 Both go to GND (0 V) �� Both pins 3 and 8 are internally the same – you can tie one or both to GND. Wiring to Arduino Example // Pin mapping int a = 7; int b = 6; int c = 4; int d = 2; int e = 1; int f = 9; int g = 10; int dp = 5; int common1 = 3; int common2 = 8; void setup() { pinMode(a, OUTPUT); pinMode(b, OUTPUT); pinMode(c, OUTPUT); pinMode(d, OUTPUT); pinMode(e, OUTPUT); pinMode(f, OUTPUT); pinMode(g, OUTPUT); pinMode(dp, OUTPUT); pinMode(common1, OUTPUT); pinMode(common2, OUTPUT); digitalWrite(common1, LOW); // Common Cathode → GND digitalWrite(common2, LOW); } void loop() { // Display “8” – all segments ON digitalWrite(a, HIGH); digitalWrite(b, HIGH); digitalWrite(c, HIGH); digitalWrite(d, HIGH); digitalWrite(e, HIGH); digitalWrite(f, HIGH); digitalWrite(g, HIGH); digitalWrite(dp, LOW); // decimal point OFF } �� Add a 220 Ω – 470 Ω resistor in series with each segment line to limit current.
