13 segment character

Forum 2005-2010 (read only) General Frequently-Asked Questions
1

Hello!
I am planning on making an led digit in 13 segment character format (see below). As the Arduino Deci has 14-2 (rx & tx) = 12 pins, how is this done? Ideally, I would like to make Pin1 = A, Pin2 = B, etc. but with only 12 pins I'm short one. Thank you for any help.

2

Hi, if you don't need the analog pins you can use them as 6 additional digital IO-Pins

This is taken from the from the reference http://www.arduino.cc/en/Reference/DigitalWrite

Note

The analog input pins can also be used as digital pins, referred to as numbers 14 (analog input 0) to 19 (analog input 5).

Eberhard

3

You can also use some kind of I/O expansion.

  1. generic I/O expansion: use a serial-to-parallel shift register (74x595) to add arbitrary bits.
  2. light one segment at a time using something like a 74x154 4to16 line decoder.
  3. Use an character-generator sort of ROM, perhaps even a serial-driven one (which almost makes it a display controller.)
  4. Use an actual display controller chip. The MX7219 seems to be popular for up to 8 segments, but Maxim also has 14 and 16 segment drivers.
4

Or just think of the LEDs as a 3x5 matrix and drive them off 8 I/O lines?

5

Or just think of the LEDs as a 3x5 matrix and drive them off 8 I/O lines?

Usually this doesn't work with this type of display because there is only a single common cathode anode. (I checked an actual datasheet before my posting.) If your particular display has multiple CC or CA pins, then this could work...

6

Usually this doesn't work with this type of display because there is only a single common cathode anode. (I checked an actual datasheet before my posting.) If your particular display has multiple CC or CA pins, then this could work...

In his original post, he said he's thinking of making an LED digit in this format. My impression was that he's doing it out of discrete LEDs, which is why I made that suggestion. Of course, that impression could be wrong.

7

Speaking noob-to-noob, I would say you should first try to do it using the arduino Output pins; getting some extra outputs with the analog pins as wayoda suggested.

Next, I would suggest you to learn how shift registers work... if you are new to those things (and clocked devices), it might be a pain to learn how it works, but it worths it as you'll understand much better how ICs work.

You can check [u]http://www.arduino.cc/en/Tutorial/ShiftOut[/u] if you actually manage to find a 74HC595.

Otherwise, you can try an alternative shift register like an SN74164, which is easier to start with but has less functions. Go to google for a datasheet.

My favorite is a shift-store register, the HCF4094, which can control leds perfectly.

my 2 cents.