Summary of White 7-segments clock ATtiny26
A compact white 7-segment digital clock built around an ATtiny26 microcontroller, using four multiplexed displays, selectable time modes, adjustable brightness, and simple pushbutton time setting. Prototype uses a 4.096 MHz crystal and discrete transistor drivers with per-segment resistors; firmware and HEX file provided for programming the ATtiny26.
Parts used in the White digital clock:
- ATtiny26
- xtal 4.096MHz
- 27pf ceramic (2x)
- 7-segment white CC (4x)
- pushbutton (2x)
- 78L05
- 47uF/16V electrolytic
- 0.1uF/16V tantalium
- 10k resistor
- 100n multilayer
- 150 Ohm resistors (8x)
- 6k8 Ohm resistors (4x)
- BC327-25 PNP transistors (4x)
1x ATtiny26
1x xtal 4.096MHz
2x 27pf ceramic
4x 7-segment white CC
2x pushbutton
1x 78L05
1x 47uF/16V electrolytic
1x 0.1uF/16V tantalium
1x 10k
1x 100n multilayer
8x 150 Ohm
4x 6k8 Ohm
4x BC327-25 PNP
Features (BETA)
1. Select Hrs/Min or Min/Sec
2. Time set/ready (single/fast-auto increment)
3. Adjustable intensity (12 steps)
System information
ATtiny26 fuses: sp12 -wF11101111
Refresh rate: 62.5 Hz
Timer1 @ ck/64 (4.096 MHz)
Timer overflow: 4 msec
Software code: 403 words
White digital clock
A white seven segments digital clock based on the AVR ATtiny26 microcontroller. On the right you see the diagram of the clock, and below a picture of the prototype. The diagram is straight forward design, eight resistors to the segments, four small signal transistors with four basis resistors. The four 7 segments displays are multiplexed, the white LED in the middle of the displays is for indicating the seconds.
Download: avrclock.zip (BETA version! (update: 24 FEB 09)
Upload the *.hex file inside the avrclock.zip file into an ATtiny26 AVR microcontroller with this programmer, and build the circuit, and you have a digital clock.
For more detail: White 7-segments clock ATtiny26
- What microcontroller does the project use?
The project uses an ATtiny26 microcontroller. - What crystal frequency is required?
The circuit uses a 4.096 MHz crystal. - How many 7-segment displays are used?
Four white common cathode 7-segment displays are used. - How is brightness adjusted?
Brightness is adjustable in 12 steps as stated in the features (BETA). - How are the displays driven?
The four 7-segment displays are multiplexed and driven via four small signal PNP transistors with base resistors. - What is the refresh rate of the display?
The refresh rate is 62.5 Hz. - What timer configuration is used for overflow timing?
Timer1 runs at clock divided by 64 with a timer overflow of 4 ms. - What files are provided to program the ATtiny26?
The avrclock.zip file contains the HEX file to upload to the ATtiny26. - What power regulation is used?
The design uses a 78L05 voltage regulator. - How many segment resistors are needed?
Eight 150 Ohm resistors are used for the segments.
