Introduction: Digital Calendar Clock Made From CMOS Chips
This is a continuation of my 24 hr clock from 2012. I organically intended to include these circuits, but ran out of time (and PCB board space) to get it done.
This is what it does:
1) It keeps track of the day of the week with 7 separate LEDs. The weekend LEDs are a different color :)
2) It keeps track of the month with 12 separate LEDs
3) It keeps track of the day of the month with 7-segment displays ... with a catch
Here are some caveats:
1) Not every month has 31 days ... I know this, but considering I wanted to do this with only basic logic and not a micro-controller, I was aiming for simplicity. So, the clock is designed to count 31 days for each month and for one more catch, it counts from 00-30. So when it rolls around to 00 it really means its the first of the month.
2) The 4017 chip normally counts to 10, but I needed it to go to 12 to display all the months of the year so two 4017 chips are connected together with an AND gate. You may have to increment the month manually from August to September, but otherwise this is the only "bug"
Lastly, this project gave me an excuse to order a cool custom laser etched case for it from ponoko.com! This is a fairly niche project because it relies on my 24 hr clock I made last year, but it could be done I suppose if it had some other daily input mechanism.
Step 1: PCB Board Layout
The PCB is a 5x8 board. A signal from my 24-hour clock increments the day of the week and day of the month via 4017 decade counters. A "seconds timer" is honestly there just to make it look a little cooler. It flashes back and forth like a metronome.
Pin 8 of the AND gate of my 24 hr clock feeds into the daily pulse input of this board and increments the day of the week and day of the month. Pin 11 of the OR gate of my 24 hr clock feeds into the second pulse input of this board and creates the metronome flashing. Be careful with the 4543 chips, they're placed upside on the board.
Digikey Parts List in brackets. The quantity are in parentheses.
(2) 74HC390 Dual Decade Counters [568-1442-5-ND]
(2) 4543 BCD to Decimal Converters [568-3138-5-ND]
(20) 1000Ω drop down resistors for 7 segment displays
(3) 10kΩ Resistors
(1) Switching Transistor 2N3904
(2) Common Anode 7-Segment Displays [160-1575-5-ND]
(21) 5 mm Green/Red/Yellow or whatever color you want LEDs
(3) 0.1 uF ceramic capacitor
(3) Momentary Switches [P8071SCT-ND]
(3) 4017 Decade Counters [296-2037-5-ND]
(1) 3-Input AND Gate [296-2064-5-ND]
(1) 5V Power Supply
Step 2: PCB Art
The actual PCB art for etching. It should come out as 5x8. I always like to place actual ICs on the paper to make sure everything lines up incase the page setup size needs to be increased or decreased slightly.
Etching the board:
1) Lightly sand the copper clad board. This seems to make the pattern stick better.
2) Set your laser printer on max toner density
3) Print out the PCB art on magazine paper. It may jam a few times, but it gives great results.
4) Iron the PCB art onto the board at your iron's maximum temperature. Apply alot of pressure for 15 minutes.
5) Soak in water to dissolve paper. Remove any excess paper.
6) Fix any broken traces with a sharpee.
7) Etch in ferric chloride which you can get at Radio Shack.
Step 3: The Final Clock
Once you're done, it's a fairly cool device. Here is the other side of the enclosure showing the 24-hr clock and a view from the top.