Wordclock 11x10 using 75HC595

Projects Programming
1

Hi everyone,

I'm planning to build my own wordclock with 11 rows and 10 columns.

I don't want to use a DCF77 for getting the time, I want my Arduino Uno both to count the minutes and hours and printing the time on the LED matrix.
(As seen here: http://www.artschoolvets.com/news/2009/08/23/wort-uhr/)

Unfortunately I couldn't find any description of how to program it. I would me very thankful for help!

By the way, is it difficult to scroll a text (like a marquee) on the LED matrix? Where can I find a tutorial about it?

Thanks for helping me,
max :slight_smile:

2

Not 11x10 or using 75HC595 but it may give you pointers.
EDIT: Added missing URL
http://arduino.cc/forum/index.php/topic,118338.0.html

3

thanks for the answer, but i don't really understand what you mean. :~

max

4

max713:
thanks for the answer, but i don't really understand what you mean. :~

Sorry, my bad. Forgot to put the URL in the reply. Have now edited the post but for completeness here it is again
http://arduino.cc/forum/index.php/topic,118338.0.html

5

Wow nice clock Riva!

You don't use a DCF77, don't you?
Ist would be very kind of you if you could send me the whole code, of course only if you have time!

Thanks!
max

6

max713:
Wow nice clock Riva!
Thanks, It was my first Arduino project.

You don't use a DCF77, don't you?
Nope, I use a DS3231 RTC module.
Ist would be very kind of you if you could send me the whole code, of course only if you have time!
Everything is in that thread. Materials/parts used, schematics and the code.

7

I would think it is quite intensive to drive the display with hc595s. I would split it into half and drive each with max7219, assuming you are running this at 5v.

8

so you think it is too complicated to write the sketch when using the hc595?

I don't know much about the MAX7219, would it be easier to work with? But they cost about 7-8€!!
What did you choose Riva?

9

It is not much about programming complexity, but more cpu capabilities.

It takes about 50us or so to date a column. With ~10 columns, that's about 0.5ms per frame so you are limited about 0.5ms for anything else, assuming a 100hz update frequency.

With the max7219, it is a load-and-forget deal: your mcu isn't involved unless you have to change the display.

10

max713:
so you think it is too complicated to write the sketch when using the hc595?

I don't know much about the MAX7219, would it be easier to work with? But they cost about 7-8€!!
What did you choose Riva?

I used MAX7219 but buying them off ebay is a lot cheaper http://www.ebay.co.uk/itm/2pcs-Original-MAX7219CNG-DIP-24-MAX7219-MAXIM-LED-Display-Drive-NEW-m-/320777447581?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item4aafd3689d
As dhenry says the nice thing about the MAX7219/MAX7221 is it takes care of all the LED scanning so your program is a lot less complex. You tell it what leds to light and that's it, you can even use the much maligned delay() with no problems.

11

is it possible to split it in:
one MAX drives 5x11
the other MAX the other 5x11?

12

max713:
is it possible to split it in:
one MAX drives 5x11
the other MAX the other 5x11?

Should work, each MAX7219 is capable of driving 64 leds so 5x11 will fit on one. Not sure if you would need to round up to the nearest 8 though (58)

13

yes I have only 8 anodes and 8 cathodes available, so 5x11 wouldn't work very fine, wouldn't it?
Now I tend more to the shift registers, although writing the sketch is not that fine comparing to MAX7219...

14

I see you have 2 threads going on the 11x10 matrix - these will be combined before too long.

15

dhenry:
It is not much about programming complexity, but more cpu capabilities.

I think it is mostly about programming complexity and output dive capability vs time/duty-cycle.
There is more than enough cpu speed/cycle-power and pins to control/drive the LEDs directly
even without using shift registers.
(Although the slow Arduino core library functions like shiftout() or digitalWrite()
may have to be jetisoned to get back CPU cycles)

For a normal word clock very few LEDs are on any any give point in time so
even duty cycle (refresh rate) is not an issue there.
What can be a potential issue is if many or all of the LEDs need to appear to be on all
at the same time.
But even then it can resolved with some additional s/w complexity to allow multiple
LEDs to be on at the same time during the multiplexing.
With shift registers, duty cycle shouldn't be an issue, particularly if you stay
away from the arduino core libraries to drive them.

Here are some (non arduino) projects that show what you can do with some
simple multiplexing:
http://www.nerdkits.com/store/NKLEDARRAY001/
http://www.nerdkits.com/videos/ledarray2/

While their design needs some current limiting resistors, it demonstrates
a way to control 120 LEDs, which on the same scale as the desired 11x2 array,
without using any other components.

--- bill