This project started when I bought (as-is) kit of a digital clock marked as (defective) for 2$ . I found that PCB is broken being hit by some sharp object in the middle causing cracks & connection cuts. I repaired the PCB and it worked. So I decided to give it a face lift.All remaining parts came free from recycle bin.
Step 1: The Parts
These parts were used to build the project
1- Damaged then repaired digital clock kit
2- AC to DC adapter harvested from a microwave oven control board. (see the photo here)
3- Holder arm harvested from a recycled table lamp which has on-ff switch died & reflector dome missing.
Step 2: Lets Start Assmble Clock Kit
Clock kit has 2 PCBs. One for control electronics which is made from a real time IC and a microcontroller. The second board is the display PCB. cracked in the middle, so I had to reconnect the cuts in the copper. Then I soldered 142 blue LEDs. After testing it, I found one LED was green so I have to replace it with blue. Sometimes bulk blue LEDs contain a few of different colors. No time to test them one by one before soldering. So it is easier to solder them first then replace dead or different color ones if any.
Step 3: Assemble and Test the Clock.
The Clock needed a 110 volt AC to 12 Volt DC..that can be found from the control board of a dead microwave oven. This nice adapter is ideal for 2 reasons, first it is designed to work 24/7 inside microwave so it is high performance. Second it comes with bridge rectifier and filter capacitor also found on the same board to be recycled from microwave oven. after assembly, the clock worked like a breeze. With standby CR2032 battery on board, the clock IC DS1307 will keep time even if the mains supply is cut.
Step 4: Wrap Up the Clock
I used an old PCB from junk as a chassis to put all the clock components together. of course since the chassis PCB is conductive, I used some plastic pieces to insulate it from the clock at the touch points. see the white plastic sheets cut in square and rectangle. since this will be some sort of a skeleton clock, notice that I used red shrink tubes to insulate the AC input pins for the little transformer.
Step 5: Add a Robotic Arm
Now to hang my clock on a wall, or attach to the roof, with flexibility to turn to any direction, I connected it to the table lamp arm using a metal angle from my ever growing junk boxes.
Tested it , all went well. Total cost was 4 hours + 2$.
I mentioned the time first because it is more valuable than money. So use it don t lose it.