1. CMPE 118 MECHATRONICS Noise Isolation Keeping the Gremlins Out

2. CMPE 118 MECHATRONICS How noise gets into your circuits

3. CMPE 118 MECHATRONICS Key Characteristics of the noise source Voltage Current Frequency Distance from the victim ‘High’ voltageStrong electric fieldCapacitive coupling ‘High dV/dtCapacitive coupling ‘High’ currentStrong magnetic fieldInductive coupling ‘High’ frequency Radiation Radiative coupling Distance = 0Direct contact Conductive coupling Distance > wavelengthProbably Radiative 0 < Distance < WavelengthCapacitive or Inductive Not For Us

4. CMPE 118 MECHATRONICS Key Characteristics of the noise source Voltage Current Frequency Distance from the victim

5. CMPE 118 MECHATRONICS What is the most likely coupling mechanism for Fluorescent light noise Arc welding noise Digital clock noise Capacitive Inductive High Voltage High Current High dv/dt

6. CMPE 118 MECHATRONICS What is the most likely coupling mechanism for Fluorescent light noise Arc welding noise Digital clock noise

7. CMPE 118 MECHATRONICS Conductive coupling Motor Sensor

8. CMPE 118 MECHATRONICS More conductive coupling +12V+5V

9. CMPE 118 MECHATRONICS How should I wire these up? 12V7.5V Motor HC11 +G GG G G+ ++ + Sensor

10. CMPE 118 MECHATRONICS Which waveform must be conductively coupled? Why?

11. CMPE 118 MECHATRONICS Identifying characteristics of conductive coupling Metallic contact required Unaffected by people or cable movement Non-zero average value for the waveform Techniques to reduce conductive coupling Break the conductive contact Use filtering

12. CMPE 118 MECHATRONICS Identifying characteristics of conductive coupling Metallic contact required Unaffected by people or cable movement Techniques to reduce conductive coupling Break the conductive contact Use filtering

13. CMPE 118 MECHATRONICS Capacitively coupled noise Simplified circuit Coupling capacitance

14. CMPE 118 MECHATRONICS Physical Representation of capacitively coupled noise

15. CMPE 118 MECHATRONICS Equivalent circuit for capacitively coupled noise If

16. CMPE 118 MECHATRONICS Reducing Capacitively coupled noise

17. CMPE 118 MECHATRONICS Reducing Capacitively coupled noise Shield Connect the shield to return the noise current to the source How many connections to the shield are required? Position the shield to intercept the noise current

18. CMPE 118 MECHATRONICS Summary of capacitive noise reduction techniques Reduce capacitive noise coupling by 1. Reducing coupling capacitance 2. Reducing circuit impedance 3. Using shielding Capacitive shielding requires 1. Proper shield location 2. Correct shield connection

19. CMPE 118 MECHATRONICS Summary of capacitive noise reduction techniques Reduce capacitive noise coupling by Capacitive shielding requires

20. CMPE 118 MECHATRONICS Isolation Why do you need it? How do you get it? Conductive noise Large voltage differential Provide fault isolation (Safety) Minimize leakage currents Magnetic coupling Optical coupling

21. CMPE 118 MECHATRONICS Isolation Why do you need it? How do you get it?

22. CMPE 118 MECHATRONICS Isolation via magnetic coupling

23. CMPE 118 MECHATRONICS PCB mount miniature relays

24. CMPE 118 MECHATRONICS Reed Relay construction

25. CMPE 118 MECHATRONICS Optical Isolation

26. CMPE 118 MECHATRONICS

35. 68HC11 PS2501 Opto-Isolator L-298 H-Bridge Create a design to connect