Report (4) 5/11/2016. Report by. First and Last Name. CETT 1321 Electronics Fabricatio '/' Spring Instructor, Khansaa Almansor

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1 Report (4) Fabrication of a Printed Circuit Board D_,i<ness Sensor Report by First and Last Name CETT 1321 Electronics Fabricatio '' Spring 2016 nstructor, Khansaa Almansor Houston Community College Houston, TX

2 First and Last Name Fabrication of a Printed Circuit Board Darkness Sensor ""' Objective: To simulate, design, etch, and solder a darkness sensor on a copper clad board. lntrod uction: PCBs physically support and hold together electronic components in a circuit as well as provide paths of conductive metal for electric charge to flow. PCBs are composed of an insulating substrate (often made from fiberglass and an epoxy resin) and a sheet of copper that is laminated on either or both sides of the board. 1 The copper is etched away from the board during manufacturing to create electrical connections between components..,, The darkness sensor circuit (Figure 1) is a simple circuit composed of a few resistors, two transistors, and a photoresistor (AKA a light dependent resistor or photocell). Photoresistors exhibit photoconductivity which means its resistance decreases with the intensity of the light it is exposed to. n the operation of this circuit once the light hitting the photoresistor decreases past a threshold the LED will begin to light up. Equipment, Tools, and Components: 1- lko resistor resistors 1-4.7KO resistor 1- CdS Photoresistor 1-9V battery 1- Light Emitting Diode 2- NTE123AP (NPN) Transistors N Multisim 14 Schematics: Microsoft Visio Bread board Copper clad PCB Permanent marker Ferric Chloride etching solution lsopropyl Alcohol Drill with 116" engraving cutter bit 40W Solder ron and soldering tools R1 1K Q1 BC547 R3 a 4.7k Figure 1. Schematic for darkness sensor. 1 ndex. php m aki ng-a-pcb-eductiona -movies Page 1 of 5

3 First and Last Name Fabrication of a Printed Circuit Board Darkness Sensor LOR 2ooka 0% Key=A R4 1ka '911' ll, U:h,1L PR5 R Vs N,J,_ Q2..=..gy BC547A, R2 4.7ka f> R eq -GR,1'1 Figure 2. The darkness sensor circuit simulated with Multisim. n this figure the variable resistor LOR simulates a photoresistor in a brightly lit environment. '""'... Vs..=..gv R4 1kQ LOR,200k0 100% Key=A..,,.., Q2 BC547A Se) R2 Cy) "'..... "".. 4.7k0 -o -.Raft Figure 3. The darkness sensor circuit simulated with Multisim. n this figure the variable resistor LOR simulates a photoresistor in a completely dark environment. Page 2 of 5

4 First and Last Name Fabrication of a Printed Circuit Board Darkness Sensor Figure 4. The darkness sensor setup on a bread board. The LED is off since the photoresistor is exposed to light. Figure 5. The darkness sensor circuit setup on a bread broad. The LED is on in this figure since the photoresistor is covered with opaque tape. Page 3 of 5

5 First and Last Name Fabrication of a Printed Circuit Board Darkness Sensor z Figure 6. Wiring diagram of the circuit made with Visio. Figure 7. The bottom of the board after etching and soldering. Page 4 of 5

6 First and Last Name Fabrication of a Printed Circuit Board Darkness Sensor Procedure: 1. Reconstruct the circuit shown in Figure 1 in Multisim. 2. Run the simulation to verify that the circuit is operationaj. (Figures 2 & 3) 3. Replicate the simulated circuit on a bread board to confirm that it is physically operational. 4. Draw out the wiring diagram to be etched on the copper board in Visio. (Figure 6) 5. Replicate the wiring diagram made in Visio on the bread board to ensure that the circuit still functions. (Figures 4 & 5) 6. Using a permanent marker copy the wiring diagram made in Visio on the copper side of the board. 7. Submerge the board in a container with ferric chloride until all the copper is removed from the board. This process can be expedited by applying heat to the solution as well as agitating it. 8. Rinse the board off and remove the permanent marker with isopropyl alcohol and a paper towel. 9. Using a drill make holes in the appropriate locations for the component leads. 10. Place and solder each component in their correct locations on the board. 11. Test the circuits operation by applying power. Conclusion: After etching and soldering the circuit on the board functioned correctly. While this particular circuit may not seem to have any practical application the same general concept could be scaled up and applied to a more powerful light source, for instance a porch light that only turns on after dusk. By following these same general steps outlined any circuit of your desire could be tested and fabricated. Page 5 of 5