3. Printer Port

4. 10 0 10 1 10 2 10 3 11000100 10 1000 * 0= 0 100 * 1= 100 10 * 6= 60 1 * 4 = 4 = 164 Decimal Binary We use Ten Symbols 0 1 2 3 4 5 6 7 8 9 2020 21212 2323 184 8 * 1 = 8 4 * 1= 4 2 * 0 = 0 1 * 1= 1 = 13 We use Two Symbols 0 1 or On Off or Hi Low or 0V 5V 2 1 6 4 1 1 0 1 2

5. Output Data 1 Data 0 Data 2 Data 4 Data 5 Data 3 Data 6 Data 7 ACK Busy Paper Empty Select StrobeInput 1 14 13 25 Initialize Printer Auto Feed Error Select Input Pins 18 – 25 Ground Output Input 8 Data Outputs (378 H) 4 Other Outputs (379 H) 5 Data Inputs (37a H)

6. 1 14 13 25 - + 5V VCC 470 ohm LED Printer Port

7. 1 14 13 25 LED 470 ohm 5 V D0 D1 D7 D2 Printer Port

8. IN+ IN- Comparator ¼ LM339 R4 3.3kohm 12V VCC R2 100kohm R3 10kohm From Printer Port R5 R1 10kohm 3.3kohm D400 1N4007 D1 X Y K2 RELAY 5 2 4 230 V AC L N 230V AC Motor V A = R5 / (R1 + R5) V A = 3.3 / 13.3 = 2.9 V A

10. 1 14 13 25 Printer Port Switch

11. 100 k Preset IN+ IN- Comparator 10kohm 12V To Printer Port Input 100kohm 5 2 4 5.6kohm ¼ LM339 LDR 1 M Preset