ATtiny Binary Clock
ATtiny Binary Clock
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Once I finished my 8x8x8 LED Cube, I had some extra LEDs and shift registers waiting to be used. I decided to make a little clock which uses 16 LEDs to show the time.
Once I finished my 8x8x8 LED Cube, I had some extra LEDs and shift registers waiting to be used. I decided to make a little clock which uses 16 LEDs to show the time.
Here's the schematic I put together. It's pretty straightforward, using 16 LEDs in a common cathode configuration.
Here's the schematic I put together. It's pretty straightforward, using 16 LEDs in a common cathode configuration.
sch2.pdfIt turns out that to display the time in binary, a minimum of 16 LEDs are needed, which neatly fits into two 8-bit shift registers. The brains lie in the bottom right IC, an ATtiny85 microcontroller. Everything is powered by a 9 volt battery passed through a linear voltage regulator.
It turns out that to display the time in binary, a minimum of 16 LEDs are needed, which neatly fits into two 8-bit shift registers. The brains lie in the bottom right IC, an ATtiny85 microcontroller. Everything is powered by a 9 volt battery passed through a linear voltage regulator.
This is the underside of the board I put together. I used 30 AWG wire wrap wire for everything (although I did not use the technique of wire wrapping to make my connections). I used 200 ohm 0805 sized surface mount resistors to limit the current on each LED.
This is the underside of the board I put together. I used 30 AWG wire wrap wire for everything (although I did not use the technique of wire wrapping to make my connections). I used 200 ohm 0805 sized surface mount resistors to limit the current on each LED.
The code I wrote was pretty basic. It manually writes different digital pins on the ATtiny to control the clock, data, and latch pins. There is one variable which increments each second in a loop. Once that variable reaches 60, it resets, and another variable corresponding to the current minute increments. Once that one reaches 60, it resets and an hour variable is incremented. The hour variable is shifted out, followed by the minute and then second variables. I didn't use any tricks to save power, meaning the LEDs are pretty much always on. If I wanted to upgrade this design, I could do a few things:
The code I wrote was pretty basic. It manually writes different digital pins on the ATtiny to control the clock, data, and latch pins. There is one variable which increments each second in a loop. Once that variable reaches 60, it resets, and another variable corresponding to the current minute increments. Once that one reaches 60, it resets and an hour variable is incremented. The hour variable is shifted out, followed by the minute and then second variables. I didn't use any tricks to save power, meaning the LEDs are pretty much always on. If I wanted to upgrade this design, I could do a few things:
Use a switching regulator to save losses generated by the linear regulator
Add an external crystal to keep precise track of the time
Up the code so that it uses persistence of vision and saves energy in the process
Increase the resistance on each output of the shift registers, trading off between brightness and power consumption
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