Introduction

Most electronic circuit today can be tested using steady DC (direct) current with only low 1.5V to 30V voltage requirement but the most common voltage source supplies an oscillating AC (alternating) current with a very high 220V to 240V output. A power supply is any means of providing electrical power to a circuit e.g. from a battery, a generator, a solar cell, etc. In electronics it is a piece of equipment that converts AC to DC current. Using a power supply, one can use a regular household receptacle outlet to provide electricity to an electronic circuit to test it.

Objective

To create a safe, reliable and effective 0V-30V DC power supply using the Schematic Diagram below.

Schematic Diagram

Parts List

QuantityCodeDescriptionRemarks

1pcTransformer30V

kgMagnetic wire#22

kgMagnetic wire#18

1pcBobbin1in

1rollFish paper

1kgE and I core

1pcRocker switch w/ indicator light

2pcBinding postRed and Black

1pcPower cord

1pcKnob

2pcFuse holder

2pcHeat sinkLarge and small

1pcMini fuse1A

1pcMini fuse3A

6pc1N5400Diode

1pc1N4001Diode

1pcTIP2955PNP Transistor

1pcLM317TVoltage Regulator

1pcResistor0.22Ohm, 5W

1pcResistor240Ohm, 1W

1pcResistor1Ohm, 5W

1pcPotentiometer5kOhms

1pc1N5363Zener Diode30V, 5W

1pcCapacitor4700F, 50V

1pcCapacitor1, 50V

1pcPanel Voltmeter0V-30V

Assembly Procedures

The assembly procedures are as follows:

1. Create a 30-volts step down transformer using the #22 magnetic wire as primary coil and #18 as secondary coil.2. Wind the primary wire with 700 turns on the 1 bobbin. Make sure the ends are long enough.3. Cover the bobbin along the wire with fish paper; make sure that the primary wire is completely covered.4. Wind the secondary wire with about 96 turns on the same bobbin. Make sure the ends are long enough5. Cover again the bobbin along the wire with fish paper. Then insert the E and I core alternating. 6. Apply metal varnish on the E and I core if desired.7. Remove the cover on the ends of the magnetic wire.8. Test the transformer and measure the output voltage.9. Design a 3 x 4 PCB diagram for the power supply from the schematic diagram.10. Etch the PCB diagram into the copper clad with Ferric chloride.11. After the PCB diagram has been etched into the copper clad, test it for any unwanted short and open connections.12. Solder into place the components except the components attached to the panel. Note: Test each component before soldering them into the copper clad.13. Fit the panel meter, black and red binding post and the potentiometer on the front panel of the chassis; the 2 fuse holder, switch and power cord on the back panel; and the PCB, transformer and heat sink inside the chassis. Outline the panel parts on the back and front panel.14. Put holes on the front and back panel, and chassis where the parts will be placed, fastened or screwed.15. Test each panel parts, then fasten them in the front and back panel.16. Test the transformer before screwing it on the chassis. Connect in series the 2 ends of the primary coil to one fuse holder, switch and power cord. Then test the connection using VOM, then test again by plugging the power cord to an outlet.17. Connect the panel parts and the transformer into the PCB. Test whether the power supply is working.18. Close the Chassis.

PCB Diagram

Figure 1 PCB DiagramParts Placement

1N40011F50V4700F50V1 5W.22 5W321ECB1N54001N54001N54001N54003A FuseLM317TIP29551N54001N54005K Pot 240 1WPOSITIVENEGATIVE1N5363Figure 2 Parts Placement

Figure 3 Top ViewFigure 4 Isometric View

Figure 5 Side ViewFigure 6 Front View

Actual Appearance (without cover)

Figure 7 Top View

Figure 8 Isometric View

Figure 9 Front View

Figure 10 Side View

Conclusion

The power supply that has been created is safe, effective and reliable. The power supply covers a small area and is very simple in design. The power supply provides a voltage output of 0.2V to 32V. The power supply is tested to work on a 12-V 5-W light bulb and can tolerate it up to 10 minutes. The power supply has 2 safety fuses to protect the circuit and the load from excessive current. The power supply has good heat sinking.

Recommendations

For best performance of the LM317, the 240-ohm resistor must be placed as close as possible to the LM317 to minimize line drops. Provide a large copper area for the ground to improve load regulation. The heat sink attached to TIP2955 and LM317 must be large enough for them not to heat up too much.

TECHNOLOGICAL UNIVERSITY OF THE PHILIPPINESTaguig CampusKm 14 East Service Road, Western Bicutan, Taguig City 1630

Electronics Engineering Department

A Final ReportSubmitted In Partial Fulfillment of the Requirements in ELE 3PA

EntitledPower Supply Unit

Submitted by:Carlon, Angelo Agustin M.BSEcE-2SE

Submitted to:Engr. Alvin ManongsongInstructor

January 6, 2014Date