9-10-2010 – Updated program added that is void of errors. I’m not sure what I was thinking 2 years ago.
11-11-2008 – Program for Picaxe chip and parts list posted. This is now a complete project! Enjoy.
11-6-2008 – New schematic and board posted! If you have any questions about how to make a PCB, please search the net before posting questions. Make and Instructables are great starting points. The program will be written and posted soon. This will be a stable clock with many improvements that were neglected in earlier projects. (Surge suppression with capacitors on the power supply, caps and a ground ring on the real time clock’s crystal)
Parts List: (Digikey.com unless noted) $55 total average cost
1 – 604-1033-ND – 1.0F cap – $3.94EA
1 – 67-1443-ND – 4-digit 7-segment display – $7.40EA
1 – 300-8301-ND – 32.768kHz crystal – $.28EA
2 – P813-ND – 10uF cap – $.14EA
2 – 490-3752-ND – 6pF cap – $.34EA (Use 3pF caps 490-3717-ND…6pF is a design error)
1 – DS1305+-ND – real time clock – $5.06EA
1 – MAX7221CNG+ – display driver -$10.81EA
6 – SW400-ND – tact switches – $.18EA
1 – CFR-25JB-4K7 – 4.7k resistor – $.06EA
1 – CFR-25JB-2K2 – 2.2k resistor – $.06EA
6 – CFR-25JB-1K0 – 1k resistor – $.06EA
8 – CFR-25JB-10K – 10k resistor – $.06EA
1 – LM7805CT – 5v voltage regulator- $.45EA
1 – PC6-S – single side copper clad board – $5.10EA
1 – 28480 – 28×1 picaxe chip – $10.50EA – HVWTECH.COM
1 – 17040 – 4MHz ceramic resonator – $1.95EA - HVWTECH.COM
1 – 1586162 – 9v 500mA wall-wart – $4.95EA – JAMECO.COM (or free from something at home)
wire,solder,etchant,IC sockets (if desired)
Photos open up in a new window. Thumbnails are used on this page for quick loading.
Left photo is the toner transfer and drilling steps.
Right photo is etching process. Acid is dark when etching is finished and is like a black mirror.
Needed: Copper clad board (6″x6″ is good), glossy photo paper, iron, permanent marker, copy machine
- Print board PDF in black/white at 100%. If you are unsure about the sizing, print it and check the hole spacing with a DIP IC. If the holes do not line up, check the Adobe print settings.
- Take your printout and a piece of glossy photo paper to the copy machine. Copy the board layout to the photo paper at the darkest setting and highest toner contrast.
- Cut out the board layout and place it toner side down onto the copper clad board. Iron it at the highest setting the iron has (I did it at 400 degrees F). Iron until the paper has completely stuck to the copper board. Allow it to cool. Once cooled, slowly peel paper and check that it has transferred (photo 1).
- If anything does not transfer, try to repeat the ironing and cooling process. If you can’t (photo 2), then use permanent marker to draw your traces (photo 3).
- Once your traces are completed, drill your holes (photo 4). Use a #67 bit (.0320) for most of your holes. Small bits are tiny, brittle, and expensive, but they are also the best hole size. Check Ebay for these if you cannot find them locally.
- Once your holes are drilled, mark them again with permanent marker in case there is any bare copper showing.
- Etch in Ferric Chloride or whatever you choose to etch with. Some people use liquid pool acid and peroxide, but it is only at your own risk (right photo).
- Once your PCB is etched, you can clean the toner and marker off with acetone and scotch brite. Make sure that the copper is nice and shiny, and avoid fingerprints, dirt, and oil once they are clean.
- Solder the parts onto the board as indicated by the board layout and schematic. This is the most time consuming part. Make sure the parts belong there before you solder. This is the main reason why the clock doesn’t work. It’s tricky to get things where they belong. TAKE YOUR TIME!
(10-15-2008) While doing quality checks on my work, I have found some errors that need to be addressed. I sincerely apologize for this. I want you to be able to learn with as little opposition as possible. This tutorial will be changed slightly. It will still be geared towards the solderless breadboard, but will also have a step to make a printed circuit board to finish your project.
(8-26-2008) Note: When designing this circuit, I left off some important items. The 7805 voltage regulator should have capacitors connected to it to suppress any surges. Capacitors do not pass DC (direct current), but a surge is somewhat like AC (alternating current), and it will send it to ground. Adding this step will create a filtered power supply. You’ll need 2 – 10uF caps rated at 25v Digikey p/n P813-ND. Connect the positive leads of the caps to the 9v and 5v pins of the 7805 (pin 1 and 3), and then connect the negative leads to the ground pin (pin 2). If you used the PCB first clock tutorial posted in July 08, just drill some holes in the traces and solder these parts in, or just solder them to the traces.