Power projects/Howard Community College/Spring2012/p2550TK
Electronic Sections Expected 
Problem Statement 
1. Repairing a ATX power supply, which is already converted to a LAB one
2. Converting more ATX power supplies to LAB ones
3. Converting other electrical boards and power supplies to LAB power supplies
Team Members 
We've got an ATX power supply which is already converted to a LAB power supply, but it does not work. We are going to figure out what is wrong with it, and repair it. After opening up the power and tracing voltage, we realized that repairing this stuff is so complicated and is beyond of our knowledge and abilities, so we gave it up. We converted two more ATX power supplies to LAB ones. Also, we made two more LAB power supplies with useless electrical boards which was a more challenging experience. We also converted a rectangular power supply to a LAB power supply.
We've got an ATX power supply which is already converted to a LAB power supply, but it does not work. We are going to figure out what is wrong with it, and repair it. We opened it up, plugged it in and measured the output voltage from the points that the wires were connected to the board. we got same results. we checked to connection of the green and a black wire. It was okay. We started tracing input voltage from the power cable to switch and to a part of the power which we guess it was transformer. There was no problem. We figured out the issue is more complicated than we thought before. It needs more knowledge and skills for solving this issue, so we gave it up. We converted two more ATX power supplies to LAB ones. In more detailed, we took power supplies from junk computers. we opened them up and cut of their sockets and extra length of wires. we got one switch, so we used it in one of the power supplies. we connected the green wire and a black wire to the switch and soldered the connections, then we covered the connections and stripped wires by electrical tape. For the other power supply we just shorted the green and a black wires. Then, we connected a 5 ohm power resistor to a red and a black wires in order to discharge capacitors. After that, we connected all remaining same-color wires to each other; blacks, oranges, reds, whites and yellows, and the blue. Next, we drilled 5 holes and attached 5 binding posts to them. Then, we connected black wires to the black binding post; oranges to the next post; reds next to oranges; yellow and white next to reds; and blue to the last binding post. Next, we soldered the connections and covered by electrical tape. Then, we closed the power and labeled the binding posts. Finally, we tested the output voltages by a multimeter. Then, we made a circuit with the power supply, a 1.5 ohm power resistor, and a multimeter that was put on the current feature. We connected the 3.3 volt binding post to the resistor and the resistor to the red lead of the multimeter and its black lead to black binding post. We measured the current. we did same for other binding posts and made a test protocol for the power supply. we got the maximum 10 amps from the power supply.
In addition, we tested a manufactured LAB power supply which was recently purchased for our class. It has two knob that allows to change the output voltage and current. This is one of the best LAB power supplies in the market because It is able to produce maximum 15 volts and 40 Amps! However, most LAB power supplies can produce maximum 1.5 Amps. we used the same circuit as above and measured its producing current. We got about 9.2 Amps from the power supply with 1.5 ohm power resistor.
Moreover, we made a LAB power supply with a useless electrical board. First, we measured its output voltages. It can produce 1.2 and 5 volt. we made a cardboard box for it. we fixed it into the box, attached 3 binding posts, and connected ground wires to the black post, 1.2 volt wires to the next post, and 5 volt wires to the last post. The board has a switch, so we made a a hole for switch and power cable in front side of the box. we taped that side tightly. Finally, we wrapped the box by Aluminum foil to make it look nicer. Then we wrapped on the Aluminum foil by clear tape because Aluminum foil can easily be damaged. Then, we tested and labeled the binding posts. Next, we made the same circuit with 1.5 ohm power resistor, a multimeter and the power supply. we measured its current. It can produce maximum 3.9 Amps. Finally, we put a label on top side of the power supply, which indicates that it works perfectly, and how much current it is able to produce.
Also, we converted a rectangular power supply to a LAB one. First, we opened it up and made its wires shorter. Then, We drilled holes for binding posts on its case. We cut off the gray and the purple wires because they were useless. Then, we shorted the green wire to a black wire to make the power run. Then, we gathered all remaining same color wires and connected them to each other.
Decision List 
- 1. Work with a square power supply
- 2. Work with a rectangle power supply
- 3. Designing a box for a board to become a power supply.
Material List 
- 1. ATX power supplies (can be taken from junk computers or purchased online)
- 2. Multimeter
- 3. Drill
- 4. Wire stripper
- 5. Binding posts (quantity depends on how many power supplies are planed to be converted),(each power supply needs at most 5)
- 6. Drill
- 7. Screwdrivers( Philips screwdrivers in different sizes)
- 8. Electrical Tape
- 9. Soldering Iron and Solder
- 10. 5 ohms Power resistors( or any combinations of two power resistors which produce the same resistance)
- 11. Computer Power Cable
- 12. Switches (optional)
- 13. 1.5 ohm(or if available 1 ohm) power resistor for measuring the maximum current produce by power supplies
- 14. Useless electrical boards, which producing DC voltages, for converting to LAB power supplies
- 15. A small carton or plastic box that fits to the electrical board
- 16. Aluminum foil
- 17. wide-clear tape
Software List 
Not any specific software
- Testing is the power supply works
- Testing if the power supply does not work
- Tutorial to drill holes on the power supply shield
- Tutorial on charging the drill's battery
- Tutorial on removing the power supply from the computer
- Tutorial on measuring the voltage with the multimeter
- Tutorial on how to convert ATX Power Supply to lab power supply
- Tutorial on how to solder
- Tutorial on how to put the cables together
- Tutorial on how to turn the power supply
- Tutorial on reducing the size of the the purple wire safety
- Tutorial on reducing the size of the gray wire in a safe way
- Tutorial on preparing the multimeter for start measuring the voltage
Next Steps 
Tips for doing this project:
1. Solder all connections carefully. w/o soldering, wires will be easily disconnected, so the power supply will stop working.
2. Use 2-3 different size of drills from thin to thick. First, make holes with the thin one and then make them bigger by the thicker one. Also, each 2 or 3 seconds, cool down the drill by oil or water. If you do not cool them down, the drills get too hot and start melting, so they lose their sharpness.
3. Use heating gun and shrink tube for covering all stripped wires and connections.
4. Be careful not to touch Capacitors or other interior parts of the power supply's board, otherwise, the possibility of electrical shock threaten you.
5. When using multimeter to determine the current of a circuit, make sure that you change the red lead's jack, otherwise, the multimeter will be damaged.
6. Also, when you measure the current of a circuit, a 1 ohm power resistor would be better. In addition, make sure that resistors when getting hot, their resistance increase, so it will affect your current calculations.
7. When working with electrical boards, make sure that you do not touch any capacitors or wires w/o gloves even when it is unplugged because capacitors can keep some power which can harm you.
8. When working on electrical boards, make sure that you immediately unplug the circuit when a part makes abnormal noise or smoke. Then, look for the possible issue(s).