Summary of Wooden LED clock using PIC16LF876A microcontroller
Summary: A simple wooden LED clock uses a PIC16LF876A microcontroller, NJU6355 real time clock, low-power MOSFETs and a 3x9 multicolor LED matrix behind a veneered MDF case. Time and date are shown by randomized LED patterns; two buttons handle display and setting. The enclosure is MDF laminated with veneer and uses a plastic grid as a diffuser/window.
Parts used in the Wooden LED clock:
- PIC16LF876A microcontroller
- NJU6355 real time clock (with 32768 Hz crystal)
- CR2032 3V lithium coin cell (backup)
- LM7805 voltage regulator
- 2N7000 low power MOSFET transistors (3 units for columns)
- Bright LEDs in four colors: amber, green, red, blue (27 total in 3x9 matrix)
- Perforated PCB/board for LED matrix
- Single-sided PCB for controller (heat toner transfer made)
- 24 gauge stranded wire
- Tactile normally open buttons (2 units)
- 10K pull-up resistors for button inputs
- Pieces of plywood or MDF (1/2" frame, 1/4" front and back panels)
- Veneer sheets (maple and others)
- Plastic grid from luminescent light fixture (front window/diffuser)
- Carpenter's glue and hot glue
- 1" wooden screws and 1/8" drill bit for pilot holes
- Wooden putty
Wooden LED clock
I really like concept. So many different types of wooden clock have been already built. I’ve seen many of them but I still don’t have my own.
What a shame. I’m going to fix it right now.
Project is very simple and requires only few common wooden materials and hand tools.
Well, part cabinets and scrap bin are over there… What can we use for this project?
– microcontroller (any kind);
– cheap real time clock;
– low power MOSFET transistors;
– bunch of super bright LEDs;
– pieces of plywood or MDF;
– few sheets of different veneer;
…
Clock case is not solid wood but MDF frame laminated by veneer.
Regular maple veneer is transparent enough and bright LED can shine through wooden surface.
Nicely finished wooden block is a beautiful decoration for geek’s room.
Multicolored lights glow deep inside wood constantly form different “alien” symbols an make device very unusual and attractive.
Yes, this clock has no digits. Instead lights of different color represent ones and tens of minutes and hours.
Step 1
Microcontroller
Clock’s brain is based on PIC16LF876A microcontroller running at 10MHz.
Only function of microcontroller is to monitor two buttons and occasionally read data from real time clock and display time and date.
Clock displays current time by turning ON and OFF predefined number of LEDs of the same color. LED pattern is chosen randomly and microcontroller generates new LED pattern every second.
If button 1 is pressed clock shows current day and month in the same manner for a 30 seconds then switches back to time showing mode. Button 2 is used to activate time or date setting mode.
Real time clock is NJU6355 chip with 4-line serial interface and operating voltage 2 – 5V.
RTC is bundled with 32768 Hz watch crystal and 3V lithium coin cell battery CR 2032 as a backup power source.
Clock’s button are normally open tactile switches.
Buttons inputs are pulled up by 10K resistors and microcontroller reads logic “1” (high level) when button’s released and logic “0” when button’s pressed.
LM7805 voltage regulator supplies 5V for whole unit. Since controller consumes low current and all LEDs are working in pulse mode, regulator stays cool and doesn’t need radiator.
LED clock 2009.zip140 KBled_clock2.zip4 KBStep 2
LED matrix
Bright LEDs of 4 different colors (amber, green, red and blue) are organized into 3 x 9 matrix.
3 columns are controlled by dedicated 2N7000 low power MOSFETs.
Maximum DC current for this type of MOSFET is 200 mA and all 9 LEDs in a column can be ON simultaneously.
9 rows are connected directly to microcontroller’s digital outputs.
LED matrix is assembled on a perforated board. All wiring is done by 24 gauge stranded wire.
Step 3
MDF box
Simple frame is made from narrow panels of 1/2″ MDF.
Before joining pieces together I’ve applied some carpenter’s glue to matching surfaces. Glue fills gaps and add extra strength to joint.
All parts fastened with 1″ wooden screws. To avoid material splitting I’ve drilled 1/8″ pilot holes for screws and made countersinks.
Front and back panels are made from 1/4″ MDF and attached to frame with glue and screws. Wooden putty can be applied over top of screw heads to make surface even and smooth.
As front window I’ve used piece of plastic grid from luminescent light fixture.
Window grid physically isolates LEDs, eliminates color mixing, forms nice illuminated dots and prevents front sheet of veneer from flexing inward. For better contrast grid is painted black.
Window frame is mounted flush with front surface and secured with hot glue.
For more detail: Wooden LED clock using PIC16LF876A microcontroller
- What microcontroller is used in the clock?
The clock uses a PIC16LF876A microcontroller running at 10MHz. - Can the clock run from a backup battery?
Yes, a CR2032 3V lithium coin cell is used as a backup for the NJU6355 RTC. - How is the LED matrix organized?
The LEDs are organized as a 3 x 9 matrix with 3 columns and 9 rows. - What controls the LED columns?
Each of the 3 columns is controlled by a 2N7000 low power MOSFET. - How are button inputs handled by the microcontroller?
Buttons are normally open tactile switches with 10K pull-up resistors; released reads as logic 1 and pressed as logic 0. - What material is used for the clock case?
The case is made from MDF frame laminated with veneer sheets. - What is used as the front window or diffuser?
A plastic grid from a luminescent light fixture is used as the front window and is painted black for contrast. - How does the clock display time without digits?
It turns on predefined numbers of LEDs of specific colors; random LED patterns represent ones and tens of minutes and hours and change every second. - Does the voltage regulator need a heatsink?
No, the LM7805 stays cool because the controller consumes low current and LEDs operate in pulse mode, so no radiator is needed.
